Pi4J Version 1.2 Release

Version 1.2 of the Pi4J Library is finally released!

The long overdue release of version 1.2 is finally here!  It's been over two year since the 1.1 release and there have been about 136 new commits to the 1.2 release which include many enhancements, optimizations, bug fixes and additional platform support for Odroid, BananaPi, BananaPro, and OrangePi boards as well as adding support for the new RaspberryPi models introduced during this time..

Pi4J Version 1.2 is also available in Maven Central.  <<View in Maven Central>>

Notable Version 1.2 Changes:

• Removed support for statically compiled wiringPi library (for Raspberry Pi).
• Added support for Raspberry Pi 3B+
• Added support for Raspberry Pi Zero W
• Added support for Raspberry Pi Compute Module 3
• Updated to Java 8 (enhancement #203)
• Updated build dependencies/plugins to latest versions.
• Removed unsupported sub-projects (pi4j-temp, pi4j-service).
• Added SPI mode support for Odroid, BananaPi, BananaPro, and OrangePi platforms.
• Added experimental support for OrangePi platform.
• Added experimental support for Synovoip BPI (BananaPi) platform.
• Added experimental support for NanoPi platform.
• Fixed #438: ArrayIndex Out of Bounds when pin address address is >= 100
• Fixed #278: wiringPiSetup*: You must only call this once per program run.
• Fixed #294; added java runtime and compiler check to pi4j helper script
• Fixed #291; W1Device name contains "\n"
• Fixed #275; LCDExample.java doesn't work in release
• Fixed #276; RaspiBcmPin pins not firing pin state change events
• Fixed #198; Problems with data from HMC5883L class
• Fixed #351; Pi4J packages excluded in OSGI manifest ImportPackage declaration
• Fixed #360; Serial.setBreak(TRUE|FALSE) is printing debug lines to stdout
• Fixed #355; ButtonBase Executor Service should be closed on GpioController.shutdown()
• Fixed #356; SystemInfoProvider CPU temperature was divided by 1000 on OrangePi
• Fixed #272; SerialDataEvent should not fire when event.length() == 0
• Fixed #361; SerialFactory isShutdown() state not getting updated on new instance

Special Thanks:

Thank You to all the Pi4J users, contributors, testers, and tinkerers for all your help and support to continue making Pi4J the go-to library for Java access to the Raspberry Pi's hardware interfaces. 

Pi4J Related Links: 

• Pi4J Website
• Pi4J Github Repository
• Pi4J Google Groups/Forum
• Pi4J JavaDoc

ModMyPiIn this article, I am reviewing the new ModMyPi PiOT Relay Board.

First Impressions

After un-boxing the relay board, my first impressions are just .. Wow!  You can tell immediately that somebody really put some thought into creating a sophisticated relay board for direct use with the Raspberry Pi. 

Most relay boards I have worked with have been either cheap (both in cost and in quality) relay boards with the most primitive of options or relay boards that I have hand-built using relays, transistors, resistors, diodes, capacitors, etc.  The nicest in terms of quality relay board I had prior to this board was the PiFace relay board.  However, it is controlled via software and SPI communication rather than direct GPIO control.  So it's a very different use case.

PiOT Relay Board

Where To Buy

You can purchase the PiOT Relay Board directly from ModMyPi for about $34 USD plus shipping.

• http://www.modmypi.com/raspberry-pi/breakout-boards/modmypi/modmypi-piot-relay-board

Features

The ModMyPi PiOT Relay Board offers the following features:

• 4 x OMRON G5LA-1 Relays for Switching up to 10A @ 250VAC, or 10A @ 24VDC
• 4 x Tactile Buttons for GPIO/Relay Bonding
• Two-Digit 7 Segment Display for Visual Feedback & Setting Control
• Micro-controlled GPIO/Relay Setting & Switching (No Jumpers Required!)
• 40 Point Raspberry Pi GPIO Modelled Input
• 5V & 3.3V Input Compatible
• Low Holding Current via PWM ~ 100mA per Relay Board
• Stackable Relay Board (Up to 5 Without External Power)
• Multiple Start-Up Modes to Negate Boot GPIO Chatter (Delayed/Handshake)
• Pi Zero Mounting Points

Installation

There are a number of installation options for connecting to your Raspberry Pi.  You can stack mount it on top of your Raspberry Pi like most shields and add-on boards.  You can use a 40-pin male connector and ribbon cable to have a flexible connection between the relay board and the Raspberry Pi.  Or if you have a Pi Zero you can surface mount the PiZero on top of the relay board.  The PiOT Relay Board Wiki has a page that demonstrates each option.  Some options may require additional parts, so you may want to consider how you will want to mount or connect the relay board to your Raspberry Pi before placing your order.

https://github.com/modmypi/PiOT-Relay-Board/wiki/Installation

Stack MountRibbon Connecrtion

PiZero - Surface Mount

For my testing, I chose to insert a 40-pin male header on the top side of the relay board and use a ribbon cable to attach to my Raspberry Pi.

Configuration

In order to control each of the four relays you must first access the configuration menu on the relay board and configure the pin numbering scheme.

See the the following link for details on how to access the configuration menu:
https://github.com/modmypi/PiOT-Relay-Board/wiki/Menu---Access 

A detailed explanation of the pin numbering schemes and a pin mapping diagram is included in the next section of this article.

After configuring the preferred pin numbering scheme, you can then following the instructions linked below to set/assign/select the GPIO pin to control each each relay:
https://github.com/modmypi/PiOT-Relay-Board/wiki/Basics 

Pin Numbering Scheme

The ModMyPi PiOT Relay Board supports a soft (software-based) mapping between each of the four relays and GPIO pins on the Raspberry Pi. The relay board allows you to configure this mapping using one of two pin numbering schemes.  Instructions for configuring your relay boards pin numbering scheme can be found here: https://github.com/modmypi/PiOT-Relay-Board/wiki/Menu---Io---Pin-Numbering

• GPIO (also known as BCM or Broadcom pin numbering)
  This numbering scheme denotes each GPIO pin by their actual GPIO number on the Broadcom SoC chipset.  This numbering scheme is the predominate numbering scheme used by the firmware, raw C code, the GPIO device driver, the GPIO Python library and more.  The SoC GPIO pins can, albeit rare, vary from model to model or RPi board revisions and may be exposed on difference physical header pins.  For this reason, this is considered a direct pin mapping where there is no software abstraction layer re-mapping pins to ensure consistency across models/board revisions.
  
  When configured for the GPIO pin numbering scheme, the relay board will display "gP" on the LED digital display. 
  
  
  
• PN (Header Pin Numbering)
  This numbering scheme denotes each GPIO pin by their physical pin location on the 40-pin GPIO header. This numbering scheme is easier to follow because the pin numbers directly match the actual (address) location on the header connector.  This pin numbering scheme is considered an abstract pin mapping because there is a software abstraction layer that is responsible for mapping the physical header pin number (address) back to the appropriate GPIO number on the Broadcom SoC.  The WiringPi C library supports addressing by header pin numbers.  
  
  When configured for the header pin numbering scheme, the relay board will display "Pn" on the LED digital display. 
   

You can use the diagram below to help map the pin numbering scheme you choose to the actual GPIO pins on your Raspberry Pi.  This pin mapping diagrams includes both of the supported pin numbering schemes supported by the ModMyPi PiOT Relay Board as well as the WiringPi/Pi4J pin numbers in case you are using the WiringPi/Pi4J pin numbering scheme in your software.  (You can click the image to download a high resolution copy of the diagram.)

Click the image above for a hi-resolution copy of the pinout diagram.

Tutorial and Documentation

There is an excellent and easy to follow set of instructions available for the ModMyPi PiOT Relay Board located on GitHub:

https://github.com/modmypi/PiOT-Relay-Board/wiki

Sample Python code is also available to help get started with your relay board.

https://github.com/modmypi/PiOT-Relay-Board

I did not use the sample code, instead I tested the board using the command line commands in the following "Testing" section of this article.

Testing

After you have configured the pin numbering scheme and have set the GPIO pin assignments for each relay you are ready to test controlling the relay by toggling the GPIO pin states between HI and LOW.  You can use the example Python program included in the PiOT Relay Wiki or you can simply use the following "gpio" command line instructions to test.

Export the GPIO Pin

The first thing we must do is export the GPIO pin as an output pin.  To do this via the gpio utility, you must to use the BCM GPIO number.  So lets use the GPIO #2 (Header Pin #3, WiringPi Pin #8) in our example.

> sudo gpio export 2 out

Control Relay in "GP" (GPIO) Pin Numbering Mode

Now we can control the GPIO assigned relay using the following commands:

Turn the relay ON; do do this we need to set GPIO#2 to the HIGH (1) state.

> sudo gpio -g write 2 1

Turn the relay OFF; do do this we need to set GPIO#2 to the LOW (0) state.

> sudo gpio -g write 2 0

(Note, the "-g" argument used with the gpio utility instructs the gpio utility to use the BCM pin numbering scheme.  Without this argument, the gpio utility would attempt to use the WiringPi pin numbering scheme by default.)

Control Relay in "PN" (Header) Pin Numbering Mode

Now we can control the GPIO assigned relay using the following commands:

Turn the relay ON; do do this we need to set GPIO on header pin #3 to the HIGH (1) state.

> sudo gpio -1 write 3 1

Turn the relay OFF; do do this we need to set GPIO on header pin #3 to the LOW (0) state.

> sudo gpio -1 write 3 0

(Note, the "-1" argument used with the gpio utility instructs the gpio utility to use the header pin numbering scheme.  Without this argument, the gpio utility would attempt to use the WiringPi pin numbering scheme by default.)

Wish List

Here are some of my thoughts as a wish list for a future version/revision of the product :-) 

I wish ... that there was a way to lock down the configuration of pin assignments once you have them configured just how you want them.  It's a bit too easy to accidentally re-map a pin when fumbling with the buttons.

I wish ... that pin assignment/configuration put the board into a mode where it would not toggle the configured relay state until the assignment was complete.  Currently as you cycle thru the pin numbers the relay toggles immediately based on the GPIO pin state of the pin number you are cycling through.    

I wish ... there was a method via software to configure pin assignments.  This way a booting application could ensure the proper pin mapping for it's needs.  This would make the board highly reusable across multiple projects without manual interaction to assign pins.   This would especially be helpful for users who potentially just download some software application to run on their system and may not be as geeky to understand or configure relay pin assignments.

I wish ... there were 4 opto-isolated inputs on the board.  The relays do a great job for outputs but often your project needs both inputs and outputs.  I realize this may be an increased cost and perhaps a different SKU at a higher price point.   

Final Thoughts

In closing, I just have to say this is a very nice board and a nice prototyping tool to have on hand when building a project that requires relay control via GPIO.  Sure its a bit more expensive than a cheap Chinese relay board, but as with most things in life .. you get what you pay for.  

I think this board is very well suited as a prototyping tool for a professional developer and also a perfect tool for for hobbyists wanting to use their Raspberry Pi's to control things and are not well versed in concepts like active-hi, active-low, coil suppression, level-shifting, etc. when interfacing to relay boards.   

The design and features of the ModMyPi PiOT Relay Board are very well thought out and offer unprecedented flexibility for relay-based projects using a Raspberry Pi.  The features I like most are the optional boot up modes, the soft-mapping of GPIO pins, the direct test button control and the friction connector allowing surface or bottom mount connections.  I can certainly see projects where just this board and a Pi Zero together comprise an elegant and compact solution for things like remote or expanded sprinkler zone controllers and other home automation projects.   

Disclaimer:

This relay board was provided to me at no cost for an honest and unbiased review.

(click to enlarge)The Pibrella add-on board serves as a simple and easy platform to get started with and learn about inputs and outputs on your Raspberry Pi.  

Pibrella is an excellent development tool for both hobbyist and students to learn about programmatic interfacing with inputs and outputs to monitor and control things in the real world. 

For beginners, three LED lights and a momentary button are provided directly on the board so you can get started playing with the input signals for the momentary button and output signals for controlling the LED lights without having to wire any circuits yourself.  

One you are ready to sense (inputs) or control (outputs) other external devices you can use the 4 generic inputs and 4 generic outputs at the bottom of the Pibrella board via the 2 8-pin header connectors.  (Note, breadboard/prototyping jump wires fit perfectly into these header blocks.) 

<<< BUY PIBRELLA ON AMAZON $22.99 with Prime Shipping >>>

More details and instructions for getting started can be found at: http://pibrella.com/

Pi4J + Pibrella

The Pibrella documentation primarily includes information about programming the Pibrella using Python.  However, we at Pi4J recognizing the Pibrella device as an excellent tool for beginners did not want to leave Java programmers out of the party.  So, we have added native support for the Pibrella board directly into Pi4J.  

Sources

The Pibrella devices interfaces can be found here:
https://github.com/Pi4J/pi4j/tree/develop/pi4j-device/src/main/java/com/pi4j/device/pibrella

An example program demonstrating the usage of the Pibrella device interface can be found here:
https://github.com/Pi4J/pi4j/blob/develop/pi4j-example/src/main/java/PiBrellaExample.java 

Example

Below is a sample program to help you get started using the Pibrella board in your Java program.

Board Layout

<<< BUY PIBRELLA ON AMAZON $22.99 with Prime Shipping >>>

Thanks to all that attended yesterday's #Devoxx "Let's Get Physical" talk on #Raspberry_Pi & #Pi4J #java #iot #raspi pic.twitter.com/3dyngd6jKY

— Robert Savage (@savageautomate) November 13, 2014

Thanks to all that attended today's #Devoxx talk on #Java 8 #Raspberry_Pi & #Pi4J with @steveonjava @JavaFXpert & me. pic.twitter.com/mbz5dH11vW

— Robert Savage (@savageautomate) November 11, 2014

Overview 

(click image to enlarge) While this is certainly far from the first article on how-to power your Raspberry Pi via POE (Power-Over-Ethernet), I thought I would go ahead and document my setup and the equipment I ordered to pull this off successfully.  

First, lets be clear -- I am using a real POE switch -- so I wanted a real POE solution for the Raspberry Pi, not one of those splitter cable solutions that simply supply a fixed power voltage over the unused pairs in a CAT5/6 ethernet cable. There is nothing wrong with that type of solution ... its pretty cost effective, but its not real POE per the IEEE 802.3af (POE) or IEEE 802.3at (POE+) specifications.   

So to pull this off, we need a POE splitter that can provide the required 5 VDC voltage and an adapter micro USB cable to plug into the Raspberry Pi's power port.  (And a short ethernet cable which you may already have laying around the house.)

Shopping List

The following items are included in this article:  

• Raspberry Pi POE to Micro USB 1m Heavy Duty DC Power Cable (LONG) ($7.80 USB + S&H)
  ~ or ~
• Raspberry Pi POE to Micro USB 8" (20cm) Heavy Duty DC Power Cable (SHORT) ($6.80 USB + S&H)
• 1 ft CAT5/6 Ethernet Patch Cable (Varies)

• TRENDnet Gigabit Power over Ethernet (PoE) Splitter, TPE-114GS  ($24.99 USD)
  ~ or ~
• TP-LINK TL-POE10R Gigabit PoE Splitter Adapter  (~ $13.74 USD)

POE Splitter

You need a POE splitter than can output 5 VDC.  I chose the TRENDnet Gigabit Power over Ethernet (PoE) splitter as it has a nice little selector switch where you can select between 5, 7.5, 9, and 12 VDC.  You don't really need the Gigabit capability for the Raspberry Pi since it only supports 10/100 Mbps and TRENDnet does make a 10/100 POE splitter model that costs a little less.  I purchased the Gigabit model thinking about other future projects I have in mind and wanted the additional speed.  

I also (later) purchased the TP-LINK TL-POE10R Gigabit PoE Splitter Adapter adapter which was less expensive and as a bonus included a short CAT-5 ethernet cable.  On the down-side it doesn't have the discrete LEDs specifically identifying which output voltage is selected, but that is a minor trade-off for the reduced cost.

Micro USB Adapter Cable

Since the POE splitter uses a barrel connector and the Raspberry Pi is powered using a micro USB connector, you will need an adapter cable to connect the POE splitter to your Raspberry Pi.  At first I was going to make my own cable from spare cables lying around the house, but then I found this pre-made adapter cable on Amazon that fits perfectly.  (Why reinvent the wheel .. Right?)

It's available in a short and long lengths:

• Raspberry Pi POE to Micro USB 1m Heavy Duty DC Power Cable (LONG) ($7.80 USB + S&H)
  ~ or ~
• Raspberry Pi POE to Micro USB 8" (20cm) Heavy Duty DC Power Cable (SHORT) ($6.80 USB + S&H)

Note:  If you would like to purchase multiple quantities of this adapter cable you can order direct from Sean Kelley at Innovative Electronic Solutions and save on combined shipping.  
http://www.innovativeelectronicsolutions.com/ 

Installation Steps

1. First, before attaching anything to the Raspberry Pi, make sure that the voltage selector on the POE splitter is set to 5 VDC. (You don't want to accidentally fry your Raspberry Pi!)
2. Connect your POE powered Ethernet cable from your network switch (or from your POE injector if you are using an injector) to the Data Power In port.  Two green LEDs should be illuminated, the POWER LED and the 5V LED.  
3. Connect the Micro USB adapter cable into the Power Out port and into the micro USB port on your Raspberry Pi.
4. Connect the short Ethernet patch cable between the Data Out port on the splitter and into the Ethernet jack on your Raspberry Pi.  

Select 5 VDC

Attach POE Ethernet Cable HereConnect power & ethernet to Raspberry Pi

Final Results

At this point your Raspberry Pi should be powered up and working.  There is not really much else to say.  Enjoy your POE powered Raspberry Pi :-)

For anyone that may have missed it, check out this article in May/June issue of Java Magazine featuring me and the Pi4J project.
http://www.oraclejavamagazine-digital.com/javamagazine_open/20140506/?pg=18&pm=1&u1=friend

	Look inside >
PI4J PROJECT

In the previous article Raspberry Pi - Installing a RS232 Serial Port we discussed how to install a RS232 port on the Raspberry Pi (model A, B, B+).  This is a follow up article provides the same information for connecting a RS232 serial cable to the new Raspberry Pi Compute Module Development board..

There are two primary RS232 interface options you can choose from for serial connectivity:  

• USB (USB to Serial Adapter)
• DB9 (Level Shifter)

Once you have a serial interface connected you can use the serial port for

• Serial Console
• Software Application

(Click one of the above options to jump to that part of the article.)

Shopping List

The following items are included in this article:

• PL2303HX USB to TTL to UART RS232 COM Cable module Converter
• MAX232 RS232 to TTL Converter Adapter Board
• 40pcs Female to Female 2.54mm 0.1 in Jumper Wires F/F 
• Jumper Wires Premium 6" F/F Pack of 10

Serial Communication via USB

If you are just looking to communicate to your Raspberry Pi via its serial UART, then you may prefer a USB interface.  Most recent models of computers and laptops do not have the traditional RS232 DB9 port anymore, so connecting using a USB port may be preferred.   

The following adapter is only $5.47 USD and it provides a USB to serial converter chip:     

• PL2303HX USB to TTL to UART RS232 COM Cable module Converter  (Buy Here)

This adapter is based on the Prolific PL2303HX chipset.  To use this USB to serial interface you will have to install a USB serial port driver on your host operating system.  Many operating systems already include support for the prolific drivers.  But in case you need it, the drivers can be found here:  http://prolificusa.com/portfolio/pl2303hx-rev-d-usb-to-serial-bridge-controller/

Below is a wiring diagram illustrating how to connect the USB to serial interface to the RaspberryPi Compute Module development board:

Photos of the connected USB to Serial interface (click to enlarge):

NOTE:  Please secure the RED lead from the USB adapter so that it does not come into contact with any of the other pins or components on the Raspberry Pi.  This RED pin carries +5VDC and could damage the Pi if it makes contact.

Now that you have the serial interface connected, you can skip down to the Serial Console section to test the interface.

Serial Communication via DB9 (Level Shifter)

For certain applications and especially projects involving interfacing with other hardware devices a standard RS232 serial device with a DB9 connector is preferred.  A standard serial port such as this does not require any drivers.  RS232 serial communication is standardized at the hardware layer.  RS232 communication can also achieve longer distance runs (maximum distance depends on baud rate).  

The following interface adapter is available for $4.50 USD:

• MAX232 RS232 to TTL Converter Adapter Board  (Buy Here)

In addition to the adapter, you will need at least 4 female to female jumper wires. 

Here are a couple of purchase options:

• 40pcs Female to Female 2.54mm 0.1 in Jumper Wires F/F 
• Jumper Wires Premium 6" F/F Pack of 10

Why is special circuitry (level shifter) needed for RS232 serial communication?

So .. what is a level shifter  and why is it needed you ask.  A level shifter is a circuit that can take the low voltage (±3.3VDC) TTL signals for serial transmit (TX) and receive (RX) from the UART on the Pi and shift them to ±5VDC the voltage signals required for RS232 standard communication.  Want to know more?  Click here.   

Below is a wiring diagram illustrating how to connect the level shifter serial interface:

Now that you have the serial interface connected, you can skip down to the Serial Console section to test the interface.
(Use a straight-thru cable for connecting to a computer.) 

Serial Console

The Debian/Raspbian distribution images include support out-of-the-box for accessing the shell console via the hardware serial port.  This can be extremely convenient if you need to access your Raspberry Pi Compute Module when it is not connected to a monitor and network remote access is not available.

Open a terminal emulation software such as Hyperterminal (Windows), Procom Plus (Windows), Indigo Terminal Emulator (Windows), minicom (Linux/OSX) or screen (Linux/OSX) and connect to the serial port using settings "115200, N, 8, 1".   You may need to press the enter key a time or two to see the prompt.  Authenticate using your credentials and you are good to go.         

Here is a screenshot of the terminal displaying the boot up information and then prompting for a login:

Software use of the Serial Port

If you intend to use the serial port for a software application running on the Raspberry Pi, there is a bit of configuration required to disable the console from using this port.   By default, the serial port is configured as a console port for interacting with the Linux OS shell.  The following steps will guide you through disabling the port from console access.

First, lets make of backup of the two files that we intend to modify.

sudo cp /boot/cmdline.txt /boot/cmdline.bak
sudo cp /etc/inittab /etc/inittab.bak

Next, we need to remove the "console=ttyAMA0,115200" and "kgdboc=ttyAMA0,115200" configuration parameters from the "/boot/cmdline.txt" configuration file. 

To edit the file use this command:

sudo nano /boot/cmdline.txt

The file probably contains this default configuration line:

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 
console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

After removing the two configuration parameters, it will look similar to this:

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 
elevator=deadline rootwait

The last step is to edit the "/etc/inittab" file and comment out the use of the "ttyAMA0" serial port.  To edit the file use this command:

sudo nano /etc/inittab

Now towards the bottom of the file, look for a configuration line that includes the "ttyAMA0" port address.

Place a pound sign ("#") in front of the line to comment it out.  With a pound sign ("#") at the beginning of the line, Linux will ignore this configuration line.  

Save the "/etc/inittab" file and then issue this command to reboot the Raspberry Pi:

sudo reboot

Now you are ready to use the serial port with a software application and the operating system won't interfere with the port.  Use the device address "ttyAMA0" in your application to access this serial port.  

If are interested in using the serial port with Java programming, please see this page: http://pi4j.com/example/serial.html

My Raspberry Pi just got a whole lot *sweeter*.

While attending JavaOne this year, Oracle announced that the Raspberry Pi foundation would soon start shipping the Oracle JDK/JVM (Java) baked into the Raspbian distribution.

Here was the official announcement on raspberrypi.org:
http://www.raspberrypi.org/archives/4920

And a day later new images were posted for download that include Oracle Java SE fully "baked in".
http://www.raspberrypi.org/archives/4959 

You can download the latest Raspian image that includes Oracle Java SE 7 here:
http://www.raspberrypi.org/downloads 

Here is a slide (photo) from the JavaOne Community Keynote where this was announced.

Photo by @yarasenger

Its a real treat to flash and boot up a fresh Raspberry Pi (Raspbian) image and Java be there without requiring additional steps to install it.

Java SE 8 - Developer Preview

If you prefer to install the JDK8 developer preview/early access version, please see this page:
Install Oracle Java SE8 (Milestone 8) Developer Preview (JDK)

Thank You

Thank You JavaOne attendees for joining my session today on I/O programming with Java using Pi4J on the Raspberry Pi.  Thank You Oracle for accepting my talk and providing the opportunity to for me to spead the embedded/IOT message.

I do plan on posting additional in-depth articles to this blog that cover how I built the demo system and the access control solution.  In the meantime,  I have posted a couple of photos from the session as well as the slides and links to the source code below.

Photos

Slides / Presentation

Source Code

All of the source code examples used in the presentation can be found here on GitHub:
https://github.com/savagehomeautomation/pi4j-javaone-demos

Here is a recent interview with Steven Chin (steveonjava) on the NightHacking Tour for my upcoming JavaOne session.

Session: CON7968 - Let’s Get Physical: I/O Programming with Java on the Raspberry Pi with Pi4J
When: Wednesday, Sep 25, 11:30 AM - 12:30 PM
Where: Hotel Nikko - Monterey I/II

Video streaming by Ustream

We will be reviewing into the fundamentals of programming with Pi4J and jumping into some real world demos of how you can use Pi4J and the Raspberry Pi platform to automate things in your life!    

Session: CON7968 - Let’s Get Physical: I/O Programming with Java on the Raspberry Pi with Pi4J
When: Wednesday, Sep 25, 11:30 AM - 12:30 PM
Where: Hotel Nikko - Monterey I/II

Abstract:

The Oracle JDK8 Developer Preview (Milestone 8) for ARM v6/7 (hard-float ABI) is now available!  
This release represents a feature complete and Oracle tested version of the JDK.

Please see Mark Reinhold's blog post for more details:  http://mreinhold.org/blog/jdk8-preview

This article will provide the necessary instructions on how to install the Oracle Java Development Kit 8 (JDK8) on your Raspberry Pi.  

Prerequisites

• Install and boot the Raspberry Pi using the Rasbian "Wheezy" (2013-07-26 or newer) image.  
• Get the Raspberry Pi's IP address.

Tools & Downloads:

All:

• Raspberry Pi  - Raspbian "Wheezy" image (2013-09-10)
• Oracle Java SE Development Kit (Select JDK Download, then Linux ARM v6/v7 VFP Hard Float ABI - jdk-7u40-linux-arm-vfp-hflt.tar.gz)

Windows:

• WinSCP

Mac-OSX:

• Cyberduck

Download the Oracle JDK for the Raspberry Pi

You can download the JDK 8 Developer Preview on this page:
https://jdk8.java.net/download.html

Select the Linux ARMv6/7 VFP, HardFP ABI distribution (jdk-8-ea-b106-linux-arm-vfp-hflt-04_sep_2013.tar.gz). 

Transfer the Oracle JDK to the Raspberry Pi

After downloading the Oracle JDK to you desktop computer, we need to transfer it over to the Raspberry Pi.  We will use SCP to transfer the file over the network.  If you are running on a Windows desktop, then download and install WinSCP.

 If you are using Mac OSX, you can download and install Cyberduck.  The screens will look different but the goals are the same.

Create a new session in WinSCP using the IP address of you Raspberry Pi.  The default authentication credentials for the Raspbian Wheezy image is username "pi" and password "raspberry".  Save the session and then login.  You may be prompted to accept the SSH fingerprint, choose "Yes" to accept and continue.

After successfully establishing a connection, select the drive and folder location in the left pane where you download the Oracle JDK file to on your local desktop system.  In the right pane is the file system on the Raspberry Pi, we will leave it in it's default location in the "pi" user's home directory.  Drag and drop the Oracle JDK file from the left pane to the right pane and WinSCP will start the file transfer process.  You will be prompted with a transfer dialog, just click the "Copy" button to start the transfer.  

When the file transfer is complete, you can close WinSCP (or CyberDuck).

Installation Procedure on Raspberry Pi

The remaining steps should be performed directly on the console of the Raspberry Pi or using a SSH terminal connection with shell access.  In the last step, we transfered the Oracle JDK file to the "pi" user's home directory.  We should be logged in as the "pi" user and already in the user's home directory.

Lets create a new directory where we will install the JDK files to. 

sudo mkdir -p -v /opt/java

Next, lets unpack the Oracle JDK .gz file using this command:

sudo tar xvzf ~/jdk-8-ea-b106-linux-arm-vfp-hflt-04_sep_2013.tar.gz -C /opt/java

The unpacking process will take a few seconds to complete.  It unpacks all the contents of the Oracle JDK gz file to a new directory named "jdk1.8.0" located in the "/opt/java" directory.

We can now delete the original .gz file as it is no longer needed 

rm ~/jdk-8-ea-b106-linux-arm-vfp-hflt-04_sep_2013.tar.gz

To complete the JDK installation we need to let the system know there is a new JVM installed and where it is located.  Use the following command to perform this task.

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/java/jdk1.8.0/bin/java" 1

And finally we also need to tell the system that we want this JDK to be the default Java runtime for the system. The following command will perform this action.

sudo update-alternatives --set java /opt/java/jdk1.8.0/bin/java

Now java is installed.  To test and verify we can execute the java command using the version argument.

java -version

You should get the following response:

That's it the Oracle JDK is installed and ready for use.

Add JAVA_HOME Environment Variable

Some Java programs require a JAVA_HOME environment variable to be configured on the system.  Add the following line to you "/etc/environment" using your favorite text editor.

JAVA_HOME="/opt/java/jdk1.8.0"

Also, edit your "~/.bashrc" file using this command

nano ~/.bashrc

and add the following two lines to the bottom of the file and save.

export JAVA_HOME="/opt/java/jdk1.8.0"
export PATH=$PATH:$JAVA_HOME/bin 

Reboot or re-login to apply the export to your environment.  

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

If you prefer to install the JDK7 release version, please see this page:
Install Oracle Java 7 SE Development Kit (JDK)  

UPDATE!

The Oracle Java SE 7 JDK/JRE now comes pre-installed in Raspbian images!
See this post for more details:  Oracle JDK/JVM Now Pre-Installed on Raspbian

The Oracle JDK7 for ARM v6/7 (hard-float ABI) is now available!  This article will provide the necessary instructions on how to install the Oracle Java Development Kit (JDK) on your Raspberry Pi.  

Prerequisites

• Install and boot the Raspberry Pi using the Rasbian "Wheezy" (2013-07-26 or newer) image.  
• Enable the Raspberry Pi for SSH remote network connections.  
  Update:  The Debian "Wheezy" image comes with SSH access enabled in the default image.
• Get the Raspberry Pi's IP address.

Tools & Downloads:

All:

• Raspberry Pi  - Raspbian "Wheezy" image (2013-09-10)
• Oracle Java SE Development Kit (Select JDK Download, then Linux ARM v6/v7 VFP Hard Float ABI - jdk-7u40-linux-arm-vfp-hflt.tar.gz)

Windows:

• WinSCP

Mac-OSX:

• Cyberduck

Download the Oracle JDK for the Raspberry Pi

You can download the Oracle Java SE Development Kit 7u40 on this page:
http://www.oracle.com/technetwork/java/javase/downloads/index.html

First, select JDK Download button under JDK SE 7, then select the Linux ARM v6/v7 VFP Hard Float AB distribution (jdk-7u40-linux-arm-vfp-hflt.tar.gz). 

Transfer the Oracle JDK to the Raspberry Pi

After downloading the Oracle JDK to you desktop computer, we need to transfer it over to the Raspberry Pi.  We will use SCP to transfer the file over the network.  If you are running on a Windows desktop, then download and install WinSCP.

 If you are using Mac OSX, you can download and install Cyberduck.  The screens will look different but the goals are the same.

Create a new session in WinSCP using the IP address of you Raspberry Pi.  The default authentication credentials for the Raspbian Wheezy image is username "pi" and password "raspberry".  Save the session and then login.  You may be prompted to accept the SSH fingerprint, choose "Yes" to accept and continue.

After successfully establishing a connection, select the drive and folder location in the left pane where you download the Oracle JDK file to on your local desktop system.  In the right pane is the file system on the Raspberry Pi, we will leave it in it's default location in the "pi" user's home directory.  Drag and drop the Oracle JDK file from the left pane to the right pane and WinSCP will start the file transfer process.  You will be prompted with a transfer dialog, just click the "Copy" button to start the transfer.  

When the file transfer is complete, you can close WinSCP (or CyberDuck).

Installation Procedure on Raspberry Pi

The remaining steps should be performed directly on the console of the Raspberry Pi or using a SSH terminal connection with shell access.  In the last step, we transfered the Oracle JDK file to the "pi" user's home directory.  We should be logged in as the "pi" user and already in the user's home directory.

Lets create a new directory where we will install the JDK files to. 

sudo mkdir -p -v /opt/java

Next, lets unpack the Oracle JDK .gz file using this command:

sudo tar xvzf ~/jdk-7u40-linux-arm-vfp-hflt.gz -C /opt/java

The unpacking process will take a few seconds to complete.  It unpacks all the contents of the Oracle JDK gz file to a new directory named "jdk1.7.0_40" located in the "/opt/java" directory.

We can now delete the original .gz file as it is no longer needed 

rm ~/jdk-7u40-linux-arm-vfp-hflt.gz

To complete the JDK installation we need to let the system know there is a new JVM installed and where it is located.  Use the following command to perform this task.

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/java/jdk1.7.0_40/bin/java" 1

And finally we also need to tell the system that we want this JDK to be the default Java runtime for the system. The following command will perform this action.

sudo update-alternatives --set java /opt/java/jdk1.7.0_40/bin/java

Now java is installed.  To test and verify we can execute the java command using the version argument.

java -version

You should get the following response:

That's it the Oracle JDK is installed and ready for use.

Add JAVA_HOME Environment Variable

Some Java programs require a JAVA_HOME environment variable to be configured on the system.  Add the following line to you "/etc/environment" using your favorite text editor.

JAVA_HOME="/opt/java/jdk1.7.0_40"

Also, edit your "~/.bashrc" file using this command

nano ~/.bashrc

and add the following two lines to the bottom of the file and save.

export JAVA_HOME="/opt/java/jdk1.7.0_40"
export PATH=$PATH:$JAVA_HOME/bin 

Reboot or re-login to apply the export to your environment.  

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

If you prefer to install the JDK8 developer preview/early access version, please see this page:
Install Oracle Java SE8 (Milestone 8) Developer Preview (JDK)

Overview

The Airlink 101 Wireless N 150 Ultra Mini-USB Adapter is another low-cost wireless network adapter for use with the Raspberry Pi.  Here is what this little adapter has going for it:  

• It is on the approved list of known working peripherals.
• Works directly attached to the Raspberry Pi USB port. 
  (Some network adapters used with the Pi require an external USB powered hub) 
• The latest Raspbian distributions come with the driver for this adapter pre-installed.  
• It's tiny!  It does not block access to the second USB port on the Raspberry Pi (Model B).  
• Supports 150 Mbps 802.11n  
• Backward compatible with 802.11b/g  
• Internal chip antenna  
• Affordable / Reasonably priced at $9.49 USD (Buy it here) 

Shopping List

• 1 @ Raspberry Pi  (see this page for more Raspberry Pi related supplies)
• 1 @ Airlink 101 Wireless N 150 Ultra Mini-USB Adapter

Photos

(Click photo to enlarge.)

Packaging / Specs

(Click image to enlarge.)

Installation

The latest Raspian distribution (Raspbian “wheezy” 2012-12-16) already includes the drivers for this adapter pre-installed.  This greatly simplifies the installation.  (If you are using a different distribution or an older distribution you may have to install the Linux driver for the Realtek RTL8192CU driver.)

Insert the Airlink 101 USB adapter into your Raspberry Pi's USB port.   Next, lets make sure that the Raspberry Pi recognizes the device.  Use the following command to verify that the Pi "sees" the Airlink 101 WiFi adapter.

lsusb

You should see the RealTek RTL8188CUS 802.11n WLAN Adapter device listed in the output.  This is the chipset used by the Airlink 101 adapter.

Now that we have verified that the Airlink 101 adapter is recognized, lets check to make sure the kernel driver is loaded.  Use the following command to list the kernel modules:

lsmod

You should see the "8192cu" kernel module loaded.  If not, try removing and re-inserting the Airlink 101 USB adapter. 

As a final validation check to make sure that the Airlink 101 adapter is ready to use, send the "iwconfig" command to display a listing of the current wireless network configuration. 

iwconfig

We are just looking to ensure that the "wlan0" adapter is present.

Now we are ready to move on to the configuration steps.

Configuration

One you have installed the adapter, verified the kernel driver is loaded, and confirmed that a wireless network interface ("wlan0") is available, you will need to configure the wireless connection settings to securely connect to your wireless network.

First, let's open the network interfaces configuration file for editing using the following command:

sudo nano /etc/network/interfaces

Make sure the following lines are added to (or un-commented in) your file

auto wlan0
allow-hotplug wlan0
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf

After modifying the network interface configuration file, we need to create the wireless configuration file. Use the following command to create (or edit) this file.

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

Add the following data to this wireless configuration file. (Replace the "_SSID_" and "_WPA_SHARED_KEY_" text with your actual SSID and WPA key values.)

network={
ssid="_SSID_"
proto=RSN
key_mgmt=WPA-PSK
pairwise=CCMP TKIP
group=CCMP TKIP
psk="_WPA_SHARED_KEY_"
}

(Note:  This configuration is intended for WPA protected wireless networks.)

Once the configuration files are complete, use the following command to restart the wireless adapter / interface.

sudo ifup wlan0

This command will restart the network interface and use the newly defined interface and wireless settings to establish a wireless network connection.  Assuming the configuration is correct, the wlan0 interface should connect and acquire an IP address.

For connection verification and an alternate way to see your assigned IP address, use the following command to list the network configuration:

ifconfig wlan0

If you have any trouble getting connected using the "ifup" command, verify your wireless connection settings and reboot your Raspberry Pi.  If you have the Raspberry Pi connected to a display you can watch the Pi attempt the connection during startup.  

That's it, hopefully you now have a WiFiPi.

* Raspberry Pi is a trademark of the Raspberry Pi foundation.

Also check out the installation instructions for installing and configuring the

>> Edimax EW-7811Un 150 Mbps Wireless 802.11bgn USB Adapter

The following article is an excellent resource describing many different wireless network configurations for Debian based distributions: 

• Debian : How to use a WiFi interface

(click image to enlarge)

I picked up a new Raspberry Pi case a few days ago from Amazon and was impressed so much that I decided to write this review article.

• SB Clear Raspberry Pi Enclosure

PROS

• Clear / See-Thru
• Great Looking
• Lightweight
• Compact
• Slot for GPIO 26P ribbon cable (P1 header)
• Access to all onboard headers / connectors / ports
• Easy disassembly for access to hardware if needed
• Minimal assembly required
• Available in multiple colors
• Screw "+" slots on bottom for mounting solution
• Ventilation slots on bottom 

CONS

• The plastic seems potentially brittle whereby constant opening and reassembly of the hard plastic shell may end up breaking the retention clips.  (I have reopened mine a number of times and no issues yet.)
• The price at $19.95 is a bit high, but with Amazon Prime free shipping on this item, that offsets the costs back into the appropriate range.  (NOTE:  This case is also available (and cheaper, but shipping costs apply) on eBay, SparkFun and Adafruit.)

I really do like this case overall and think it is my personal favorite so far.  It is very compact and will make an excellent travel case for my Pi on the go.   

You can purchase this case via the link below directly on Amazon:

• SB Clear Raspberry Pi Enclosure 

Here are additional photos.  Click any of the images to enlarge hi-resolution photo.

The Oracle JDK8 for ARM with support for hard-float ABI is now available as a developer preview edition!  This article will provide the necessary instructions on how to install the Oracle Java SE 8 (with JavaFX) Developer Preview for ARM on your Raspberry Pi.  

Prerequisites

• Install and boot the Raspberry Pi using the latest Raspbian "Wheezy" (2012-12-16-wheezy-raspbian.zip) image.  
  (This is the first Oracle JDK compatible with the Raspian "Wheezy" image) 
• Get the Raspberry Pi's IP address.

Tools & Downloads:

All:

• Raspberry Pi Raspbian "Wheezy" image (2012-12-16)
• Java SE 8 (with JavaFX) Developer Preview for ARM

Windows:

• WinSCP

Mac-OSX:

• Cyberduck

Download the Oracle JDK for the Raspberry Pi

You can download the Oracle Java SE 8 (with JavaFX) Developer Preview for ARM on this page:
http://jdk8.java.net/fxarmpreview/

Transfer the Oracle JDK to the Raspberry Pi

After downloading the Oracle JDK to you desktop computer, we need to transfer it over to the Raspberry Pi.  We will use SCP to transfer the file over the network.  If you are running on a Windows desktop, then download and install WinSCP.

 If you are using Mac OSX, you can download and install Cyberduck.  The screens will look different but the goals are the same.

Create a new session in WinSCP using the IP address of you Raspberry Pi.  The default authentication credentials for the Debian Squeeze image is username "pi" and password "raspberry".  Save the session and then login.  You may be prompted to accept the SSH fingerprint, choose "Yes" to accept and continue.

After successfully establishing a connection, select the drive and folder location in the left pane where you download the Oracle JDK file to on your local desktop system.  In the right pane is the file system on the Raspberry Pi, we will leave it in it's default location in the "pi" user's home directory.  Drag and drop the Oracle JDK file from the left pane to the right pane and WinSCP will start the file transfer process.  You will be prompted with a transfer dialog, just click the "Copy" button to start the transfer.  

When the file transfer is complete, you can close WinSCP (or CyberDuck).

Installation Procedure on Raspberry Pi

The remaining steps should be performed directly on the console of the Raspberry Pi or using a SSH terminal connection with shell access.  In the last step, we transfered the Oracle JDK file to the "pi" user's home directory.  We should be logged in as the "pi" user and already in the user's home directory.

Lets create a new directory where we will install the JDK files to. 

sudo mkdir -p -v /opt/java

Next, lets unpack the Oracle JDK .gz file using this command

tar xvzf ~/jdk-8-ea-b36e-linux-arm-hflt-29_nov_2012.tar.gz

The unpacking process will take a few seconds to complete.  It unpacks all the contents of the Oracle JDK tz file to a new directory named "jdk1.8.0" located in the user's home directory.

With the unpack complete its now time to move the new unpacked directory to the Java install location that we created earlier under "opt/java".  

sudo mv -v ~/jdk1.8.0 /opt/java

We can also delete the original .gz file as it is no longer needed 

rm ~/jdk-8-ea-b36e-linux-arm-hflt-29_nov_2012.tar.gz

To complete the JDK installation we need to let the system know there is a new JVM installed and where it is located.  Use the following command to perform this task.

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/java/jdk1.8.0/bin/java" 1

And finally we also need to tell the system that we want this JDK to be the default Java runtime for the system. The following command will perform this action.

sudo update-alternatives --set java /opt/java/jdk1.8.0/bin/java

Now java is installed.  To test and verify we can execute the java command using the version argument.

java -version

You should get the following response:

That's it the Oracle JDK is installed and ready for use.

Add JAVA_HOME Environment Variable

Some Java programs require a JAVA_HOME environment variable to be configured on the system.  Add the following line to you "/etc/environment" using your favorite text editor.

JAVA_HOME="/opt/java/jdk1.8.0"

Also, edit your "~/.bashrc" file using this command

nano ~/.bashrc

and add the following two lines to the bottom of the file and save.

export JAVA_HOME="/opt/java/jdk1.8.0"
export PATH=$PATH:$JAVA_HOME/bin 

Reboot or re-login to apply the export to your environment.  

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

The Oracle JDK for ARM is now available!  This article will provide the necessary instructions on how to install the Oracle Java Development Kit (JDK) on your Raspberry Pi.  

Prerequisites

• Install and boot the Raspberry Pi using the Debian "Wheezy" (2012-08-08 soft-float) image.  
  (The Oracle JDK is not currently compatible with the Raspian "Wheezy" image) 
• Enable the Raspberry Pi for SSH remote network connections.  
  Update:  The Debian "Wheezy" image comes with SSH access enabled in the default image.
  (Here is an article on how to enable SSH in the Debian Squeeze distribution)
• Get the Raspberry Pi's IP address.

Tools & Downloads:

All:

• Raspberry Pi Debian "Wheezy" image (2012-08-08)
• Oracle Java SE Development Kit (Select JDK Download, then Linux ARM - jdk-7u10-linux-arm-sfp.tar.gz)

Windows:

• WinSCP

Mac-OSX:

• Cyberduck

Download the Oracle JDK for the Raspberry Pi

You can download the Oracle Java SE Development Kit 7u10 on this page:
http://www.oracle.com/technetwork/java/javase/downloads/index.html

First, select JDK Download button under JDK SE 7, then select the Linux ARM JDK7 SE distribution (jdk-7u10-linux-arm-sfp.gz). 

Transfer the Oracle JDK to the Raspberry Pi

After downloading the Oracle JDK to you desktop computer, we need to transfer it over to the Raspberry Pi.  We will use SCP to transfer the file over the network.  If you are running on a Windows desktop, then download and install WinSCP.

 If you are using Mac OSX, you can download and install Cyberduck.  The screens will look different but the goals are the same.

Create a new session in WinSCP using the IP address of you Raspberry Pi.  The default authentication credentials for the Debian Squeeze image is username "pi" and password "raspberry".  Save the session and then login.  You may be prompted to accept the SSH fingerprint, choose "Yes" to accept and continue.

After successfully establishing a connection, select the drive and folder location in the left pane where you download the Oracle JDK file to on your local desktop system.  In the right pane is the file system on the Raspberry Pi, we will leave it in it's default location in the "pi" user's home directory.  Drag and drop the Oracle JDK file from the left pane to the right pane and WinSCP will start the file transfer process.  You will be prompted with a transfer dialog, just click the "Copy" button to start the transfer.  

When the file transfer is complete, you can close WinSCP (or CyberDuck).

Installation Procedure on Raspberry Pi

The remaining steps should be performed directly on the console of the Raspberry Pi or using a SSH terminal connection with shell access.  In the last step, we transfered the Oracle JDK file to the "pi" user's home directory.  We should be logged in as the "pi" user and already in the user's home directory.

Lets create a new directory where we will install the JDK files to. 

sudo mkdir -p -v /opt/java

Next, lets unpack the Oracle JDK .gz file using this command

tar xvzf ~/jdk-7u10-linux-arm-sfp.gz

The unpacking process will take a few seconds to complete.  It unpacks all the contents of the Oracle JDK tz file to a new directory named "jdk1.7.0_10" located in the user's home directory.

With the unpack complete its now time to move the new unpacked directory to the Java install location that we created earlier under "opt/java".  

sudo mv -v ~/jdk1.7.0_10 /opt/java

We can also delete the original .tz file as it is no longer needed 

rm ~/jdk-7u10-linux-arm-sfp.gz

To complete the JDK installation we need to let the system know there is a new JVM installed and where it is located.  Use the following command to perform this task.

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/java/jdk1.7.0_10/bin/java" 1

And finally we also need to tell the system that we want this JDK to be the default Java runtime for the system. The following command will perform this action.

sudo update-alternatives --set java /opt/java/jdk1.7.0_10/bin/java

Now java is installed.  To test and verify we can execute the java command using the version argument.

java -version

You should get the following response:

That's it the Oracle JDK is installed and ready for use.

Add JAVA_HOME Environment Variable

Some Java programs require a JAVA_HOME environment variable to be configured on the system.  Add the following line to you "/etc/environment" using your favorite text editor.

JAVA_HOME="/opt/java/jdk1.7.0_10"

Also, edit your "~/.bashrc" file using this command

nano ~/.bashrc

and add the following two lines to the bottom of the file and save.

export JAVA_HOME="/opt/java/jdk1.7.0_10"
export PATH=$PATH:$JAVA_HOME/bin 

Reboot or re-login to apply the export to your environment.  

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

Announcing the release of Version 0.0.4 of the Pi4J project!

Version 0.0.4 is the first "official" release of the Pi4J project.  Development snapshot builds have been available since September but now an official release is available complete with an installer and a number of sample projects to help you get started.    

Project Summary

This project is intended to provide a bridge between the native hardware and Java for full access to the Raspberry Pi in with a Java-friendly object-oriented approach.  Pi4J provides a set of advanced features that make working with the Raspberry Pi an easy to implement and more convenient experience for Java developers.   

>> View original project announcement.

Pi4J Project Website

The Pi4J website content has been updated with instructions and examples for 0.0.4.

• http://www.pi4j.com

Follow @Pi4J on Twitter

The Pi4J project now posts announcements on Twitter.  
Follow us to get the latest Pi4J release notices and other Pi4J news.

Follow @pi4j  

Pi4J Google Groups - Forums

The Pi4J project has started a Pi4J Google Groups forum for community discussions on Pi4J project development.

• https://groups.google.com/forum/#!forum/pi4j  

Raspberry Pi Java Forums

For general questions and support try posting to the Java topic on the Raspberry Pi community forums:

• Raspberry Pi > Programming > Java 

New Installation Package

Version 0.0.4 introduces a new installer package that makes it easy to install the Pi4J libraries and examples on a Raspbian / Debian OS distribution.  See the link below for instructions on downloading and installing Pi4J.

• http://pi4j.com/install.html

Maven Central

With the release of 0.0.4, the Pi4J project artifacts are now available on Maven Central:

• http://search.maven.org/#search|ga|1|pi4j

Release Notes - Version 0.0.4

2012-12-16 :: 0.0.4

• Added support for building a Pi4J .deb installer package for Debian/Raspian Linux distribution. (BETA)
• Modified NetworkInfo static methods to permit empty array return values when a network property cannot be obtained.https://github.com/Pi4J/pi4j/issues/3
• Fixed issue in newer Raspberry Pi 512mb firmware where Pi4J was not compiled against latest wiringPi library and thus not detecting the hardware properly. https://github.com/Pi4J/pi4j/issues/3
• Fixed defect where Pi4J library prevented consuming program from exiting properly. https://github.com/Pi4J/pi4j/issues/4 | https://github.com/Pi4J/pi4j/issues/6
• Added support for MCP23008 GPIO Provider using I2C bus.
• Added support for MCP23017 GPIO Provider using I2C bus.
• Modified build script to support concurrent soft-float and hard-float native library builds
• Modified build script to include pulling wiringPi sources and compiling when building native library
• Added power controller device interface, base impl, and reference impl
• Added GpioController.provisionXXXPin methods that allow name to be optional
• Relocated project downloads location to google code site; github deprecated downloads.
• Added Google Groups discussion forum to project docs.
• Added getTag() and setTag() to GpioPin interface and impl.
• Added TemperatureConversion utility.
• Added optional blocking argument to GpioPin pulse method to support blocking pulse invocations

>> Click here to see the full: Release Notes

Getting Started

To get started using the Pi4J library, please see the Usage page and review each of the examples to explore the functionality provided by the Pi4j library.

Overview

Overview

> sudo apt-get install openjdk-7-jdk

> wget https://github.com/downloads/savagehomeautomation/raspi-sspc/raspi-sspc-1.0.0.jar

> wget https://github.com/downloads/Pi4J/pi4j/pi4j-core-0.0.3-SNAPSHOT.jar

> sudo java -classpath classes:./'*' SSPC

> sudo java -classpath classes:./'*' SSPC -longitude=-73.985538 -latitude=40.748362

Oracle announces EA builds for Linux ARM hard float ABI will be available by the end of the year. #javaonebrasil

— Java (@java) December 4, 2012

This is great news for Java programmers on the Raspberry Pi!  See this earlier post on JVM benchmarks using the current Oracle JDK for soft-float.

I will post updates to the Oracle JVM installation instructions and benchmarks articles when the new JVM for hard-float becomes available.

While working on The Pi4J Project, I found the need to have some type of GPIO prototyping board to quickly visualize the state of GPIO pins and control the state of GPIO pins.   I purchased a handful of electronics parts and set out to build my GPIO testing board.

The picture below is the final result of building this test board:

Design Goals

My design goals included:

• Support 7 GPIO pins.
• Small/compact footprint.
• Connect to Raspberry Pi via ribbon cable.
• Support for momentary and fix on/off switches.
• Display GPIO state using LEDs.
• Captive screw terminals for connecting GPIO pins to external devices.
• Order the GPIO test IO hardware based on the Pi4J/WiringPi pin numbering scheme. 

Supplies / Parts

I purchased most of the parts used in this project on eBay.  

• 1 @ 26P ribbon cable (1 meter or less)
• 2 @ 26P female IDC connectors (press-fit)
• 1 @ 26P box header IDC male sockets (right angle or straight)
• 7 @ 1.5 VDC red LED
• 7 @ 220 ohm resistors
• 7 @ 0.3A DC 50V Mini Vertical Slide Switch SPDT 3 Pin PCB
• 7 @ 6mm x 5mm Panel PCB Momentary Tactile Tact Push Button Switch DIP (normally open)
• 4 @ 3pin Block Terminal screw connector 5mm pitch
• Solder (lead-free)
• Scrap wire

Tools Needed

• Wire snips (Hakko CHP170 Micro Cutter, 16AWG Clean Cut)
• Wire strippers (Paladin Tools 1118 GripP 20 Wire Stripper/Cutter, 30-20 AWG)
• Solder Iron (Weller WLC100 40-Watt Soldering Station)
• Digital Multimeter w/ Continuity Testing (Extech MN35 Digital Mini MultiMeter)

Logic

• When a GPIO pin is configured as an OUTPUT pin and its state is set to HIGH, the corresponding LED should be ON. (+3.3 VDC is delivered to the anode lead of the LED)
• When a GPIO pin is configured as an OUTPUT pin and its state is set to LOW, the corresponding LED should be OFF. (0 VDC is delivered to the anode lead of the LED)
• When a GPIO pin is configured as an INPUT pin and the correspondingly momentary switch is depressed or the toggle switch is in the ON position, the LED should be ON and +3.3 VDC is delivered to the GPIO pin on the Pi.
• When a GPIO pin is configured as an INPUT pin and the correspondingly momentary switch is not depressed and the toggle switch is in the OFF position, the LED should be OFF and 0 VDC is delivered to the GPIO pin on the Pi.

Wiring Diagram

The following illustration depicts the wiring schematic used to create this GPIO test board.

(NOTE:  The GPIO pin numbering is based on the Pi4J/WiringPi GPIO pin numbering scheme.  But of course you can apply whatever GPIO pin numbering scheme to meet your needs.)

Click diagram to enlarge.

Photos

Click any photo to enlarge.

Videos

This is a simple demonstration video of this GPIO test board in action with a simple Java program cycling states on the 7 GPIO output pins.

In the previous article Raspberry Pi - Installing a RS232 Serial Port we discussed how to install a RS232 port on the Raspberry Pi.  This is a follow up article to suggest a few alternative interface options as the XBit RS232 level-shifter board has been unavailable (sold out) for while now.

There are two primary RS232 interface options you can choose from for serial connectivity:  

• USB (USB to Serial Adapter)
• DB9 (Level Shifter)

Once you have a serial interface connected you can use the serial port for

• Serial Console
• Software Application

(Click one of the above options to jump to that part of the article.)

Shopping List

The following items are included in this article:

• PL2303HX USB to TTL to UART RS232 COM Cable module Converter
• MAX232 RS232 to TTL Converter Adapter Board
• 40pcs Female to Female 2.54mm 0.1 in Jumper Wires F/F 
• Jumper Wires Premium 6" F/F Pack of 10

Serial Communication via USB

If you are just looking to communicate to your Raspberry Pi via its serial UART, then you may prefer a USB interface.  Most recent models of computers and laptops do not have the traditional RS232 DB9 port anymore, so connecting using a USB port may be preferred.   

The following adapter is only $5.47 USD and it provides a USB to serial converter chip:     

• PL2303HX USB to TTL to UART RS232 COM Cable module Converter  (Buy Here)

This adapter is based on the Prolific PL2303HX chipset.  To use this USB to serial interface you will have to install a USB serial port driver on your host operating system.  Many operating systems already include support for theserolific drivers.  But in case you need it, the drivers can be found here:  http://prolificusa.com/portfolio/pl-2303hx-usb-to-serial-bridge-controller/

Below is a wiring diagram illustrating how to connect the USB to serial interface:

Photos of the connected USB to Serial interface (click to enlarge):

NOTE:  Please secure the RED lead from the USB adapter so that it does not come into contact with any of the other pins or components on the Raspberry Pi.  This RED pin carries +5VDC and could damage the Pi if it makes contact.

Now that you have the serial interface connected, you can skip down to the Serial Console section to test the interface.

Serial Communication via DB9 (Level Shifter)

For certain applications and especially project involving interfacing with other hardware devices a standard RS232 serial device with a DB9 connector is preferred.  A standard serial port such as this does not require any drivers.  RS232 serial communication is standardized at the hardware layer.  RS232 communication can also achieve longer distance runs (maximum distance depends on baud rate).  

The following interface adapter is available for $9.99 USD:

• MAX232 RS232 to TTL Converter Adapter Board  (Buy Here)

In addition to the adapter, you will need at least 4 female to female 2.54mm .1 in jumper wires. 

Here are a couple of purchase options:

• 40pcs Female to Female 2.54mm 0.1 in Jumper Wires F/F 
• Jumper Wires Premium 6" F/F Pack of 10

Why is special circuitry (level shifter) needed for RS232 serial communication?

So .. what a level shifter  and why is it needed you ask.  A level shifter is a circuit that can take the low voltage (±3.3VDC) TTL signals for serial transmit (TX) and receive (RX) from the UART on the Pi and shift them to ±5VDC the voltage signals required for RS232 standard communication.  Want to know more?  Click here.   

Below is a wiring diagram illustrating how to connect the level shifter serial interface:

Now that you have the serial interface connected, you can skip down to the Serial Console section to test the interface.
(Use a straight-thru cable for connecting to a computer.) 

Serial Console

The Debian/Raspbian distribution images include support out-of-the-box for accessing the shell console via the hardware serial port.  This can be extremely convenient if you need to access your Raspberry Pi when it is not connected to a monitor and network remote access is not available.

Open a terminal emulation software such as Hyperterminal, Procom Plus, or Indigo Terminal Emulator and connect to the serial port using settings "115200, N, 8, 1".   You may need to press the enter key a time or two to see the prompt.  Authenticate using your credentials and you are good to go.         

Here is a screenshot of the terminal displaying the boot up information and then prompting for a login:

Software use of the Serial Port

If you intend to use the serial port for a software application running on the Raspberry Pi, there is a bit of configuration required to disable the console from using this port.   By default, the serial port is configured as a console port for interacting with the Linux OS shell.  The following steps will guide you through disabling the port from console access.

First, lets make of backup of the two files that we intend to modify.

sudo cp /boot/cmdline.txt /boot/cmdline.bak
sudo cp /etc/inittab /etc/inittab.bak

Next, we need to remove the "console=ttyAMA0,115200" and "kgdboc=ttyAMA0,115200" configuration parameters from the "/boot/cmdline.txt" configuration file. 

To edit the file use this command:

sudo nano /boot/cmdline.txt

The file probably contains this default configuration line:

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 
console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

After removing the two configuration parameters, it will look similar to this:

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 
elevator=deadline rootwait

The last step is to edit the "/etc/inittab" file and comment out the use of the "ttyAMA0" serial port.  To edit the file use this command:

sudo nano /etc/inittab

Now towards the bottom of the file, look for a configuration line that includes the "ttyAMA0" port address.

Place a pound sign ("#") in front of the line to comment it out.  With a pound sign ("#") at the beginning of the line, Linux will ignore this configuration line.  

Save the "/etc/inittab" file and then issue this command to reboot the Raspberry Pi:

sudo reboot

Now you are ready to use the serial port with a software application and the operating system won't interfere with the port.  Use the device address "ttyAMA0" in your application to access this serial port.  

If are interested in using the serial port with Java programming, please see this page: http://pi4j.com/example/serial.html

Announcing the Pi4J project!

This project is intended to provide a bridge between the native hardware and Java for full access to the Raspberry Pi in with a Java-friendly object-oriented approach.  Pi4J is an open source project developed by professional software engineers.  In addition to the basic raw hardware access functionality, this project also attempts to provide a set of advanced features that make working with the Raspberry Pi an easy to implement and more convenient experience for Java developers.   

Project Website

• http://www.pi4j.com

Source Repository

• https://github.com/Pi4J/pi4j/

Basic Features

• Export & unexport GPIO pins
• Configure GPIO pin direction
• Configure GPIO pin edge detection
• Control/write/set GPIO pin states
• Read GPIO pin states
• Send & receive data via RS232 serial communication

Advanced Features

• Pulse GPIO pin states
• Listen for GPIO pin state changes (interrupt-based events; not polling)
• Automatically set GPIO states on program termination (GPIO shutdown)
• Triggers for automation based on pin state changes
• Access system information and network information from the Raspberry Pi
• Wrapper classes for direct access to WiringPi Library from Java

Getting Started

To get started using the Pi4J library, please see the Usage page and review each of the examples below to explore the functionality provided by the Pi4j library.

• Control GPIO
• Listen for GPIO Events
• Shutdown GPIO
• Trigger GPIO on Events
• Serial Communication
• System/Network Information

Simple Usage Example

Below is a simple example demonstrating controlling a single GPIO pin state.
(Please visit this page for a more in-depth view of this example: Control GPIO Example) 

public static void main(String[] args) throws InterruptedException
{
    System.out.println("<--Pi4J--> GPIO Control Example ... started.");
        
    // create gpio controller
    Gpio gpio = GpioFactory.createInstance();
        
    // provision gpio pin #01 as an output pin and turn on
    GpioPin pin = gpio.provisionOuputPin(Pin.GPIO_01, "MyLED", 
                                                PinState.HIGH);
    System.out.println("--> GPIO state should be: ON");
        
    Thread.sleep(5000);
        
    // turn off gpio pin #01
    pin.low();
    System.out.println("--> GPIO state should be: OFF");

    Thread.sleep(5000);

    // toggle the current state of gpio pin #01 (should turn on)
    pin.toggle();
    System.out.println("--> GPIO state should be: ON");

    Thread.sleep(5000);

    // toggle the current state of gpio pin #01  (should turn off)
    pin.toggle();
    System.out.println("--> GPIO state should be: OFF");
        
    Thread.sleep(5000);

    // turn on gpio pin #01 for 1 second and then off
    System.out.println("--> GPIO state should be: ON for only 1 second");
    pin.pulse(1000);
}

Stay tuned ... more articles to come on using the Pi4J library.

Just a quick experiment powering the Raspberry Pi using the 5VDC and GND pins via the 26P GPIO header.   The Pi powered up with no problems including providing sufficient power for my direct attached Edimax EW-7811Un 150 Mbps Wireless 11b|g|n Nano Sized USB Adapter.  I was able to remotely connect to the Pi using the WiFi connection and control the GPIO pins.  

Important Note!  

Please be aware that if you attempt this, you should use a regulated power supply.  Don't connect a battery pack or unregulated power supply unless you are using a voltage regulation circuit. Un-filtered/unregulated power may cause damage to you Pi.  

You can see the specific header pins used in the photo below:

• PIN 2   =   +5VDC (VCC)    (Red wire in photo)
• PIN 6   =   GROUND           (Green wire in photo)

* Raspberry Pi is a trademark of the Raspberry Pi foundation.

I received my Pi Box from Adafruit and immediately assembled the kit.  

I love the size and look of this case.  

PROS:

• Clear / See-Thru
• Great Looking
• Lightweight
• Compact
• Slot/Slit for GPIO 26P ribbon cable
• Easy disassembly for access to hardware if needed

CONS

• Assembly required
• The plastic panels all comes with the protective film which I appreciate, but removing this protective film can be a chore.
• The panels fit together and snap to lock in place; however the panels are somewhat loose fitting and the assembled enclosure can feel a bit "loose".  
  (There is nothing structurally wrong with the design, I just wish it had a tighter, more solid fit.)    
• The price at $15 feel a bit high for 6 plastic panels that I had to remove the films and assemble.  (Probably due to low production volumes.)
  
  

Despite the CONS listed, I really do like this case overall.  There is room for improvement but this is great looking simple little case.  For assembly time, expect around 20-30 minutes.    

You can purchase this case via the link below:
https://www.adafruit.com/products/859 

Here are a few additional photos.  Click any of the images to enlarge.

* Raspberry Pi is a trademark of the Raspberry Pi foundation.

For users wanting to beginning working with the Raspberry Pi, here is a shopping list for the necessary supplies, optional components and other learning resources to get started.

Raspberry Pi

• Raspberry Pi - Model B (from Farnell/Newark)
• Raspberry Pi - Model B (from RS Components/Allied Electronics)

Books

• Raspberry Pi User Guide (Personally Read) 
• Programming the Raspberry Pi: Getting Started with Python
• Getting Started with Raspberry Pi
• Meet the Raspberry Pi
• Beginning Raspberry Pi
• Raspberry Pi - A Complete Beginner's Guide

Power Supply (5 VDC, at least 700 mA)

• Motorola Micro-USB Home and Travel Charger
• Apple iPhone Charger (1A)  (Personally Tested) 
• USB to Micro-USB Cable
• Adafruit 5V 1A USB Power Supply
• AmazonBasics USB Cable - 2.0 A Male to Micro B (6 Feet / 1.8 Meters) (Personally Tested)

SD Memory Card (4GB or above)

• AmazonBasics 8 GB SDHC Card (Class 10)
• AmazonBasics 16 GB SDHC Card (Class 10) (Personally Tested) 
• AmazonBasics 32 GB SDHC Card (Class 10)
• Transcend 8 GB SDHC Card (Class 10)   (Personally Tested) 
• Transcend 16 GB SDHC Card (Class 10)  (Personally Tested) 
• Transcend 32 GB SDHC Card (Class 10)

HDMI Cable

• AmazonBasics HDMI Cable (2 meters) - If your display supports HDMI input (Personally Tested)
• AmazonBasics HDMI to DVI Cable (3 meters) - If your display only supports DVI input (Personally Tested) 
• HDMI to Display Port Cable (10 feet) - If your display only supports Display Port

Network 

• AmazonBasics RJ45 Cat5e Ethernet Patch Cable (4.2 Meters)
• AmazonBasics RJ45 Cat5e Ethernet Patch Cable (15.2 Meters)

Wireless Network (Optional)

• Edimax EW-7811Un 150 Mbps Wireless 11b|g|n Nano Sized USB Adapter  (Personally Tested) 
  >> Review & Installation Instructions 
• Airlink 101 Wireless N 150 Ultra Mini-USB Adapter  (Personally Tested) 
  >> Review & Installation Instructions  

USB Keyboard & Mouse

• AmazonBasics Wired USB Keyboard (Black)
• AmazonBasics Wired USB Mouse (Black)
• Logitech Desktop MK120 Mouse and keyboard Combo 

Case / Enclosure (Optional)

• SB Clear Raspberry Pi Enclosure    (Personally Tested > REVIEW) 
• Multicomp Clear Raspberry Pi Enclosure
• ModMyPi Cases
• Bud Industries PS-11591 Red Plastic Enclosure (Personally Tested) 
• Adafruit Pi Box   (Personally Tested > REVIEW) 
• Pilbow

Powered USB Hub (Optional)

• Macally Mini 4-Port USB 2.0 Hub with AC Adapter
• Macally Mini 7-Port USB 2.0 Hub with AC Adapter
• D-Link DUB-H7 High Speed USB 2.0 7-Port Hub
• D-Link DUB-H4 High Speed USB 2.0 4-Port Hub

Expansion (Optional - Programming)

• Gertboard  (Buy)
• Adafruit Pi Plate
• Adafruit Pi Dish
• Adafruit USB to TTL Serial Cable - Debug/Console (Personally Tested) 
• Adafruit Pi Cobler (Personally Tested) 
• Xbit Electronics RS-232 Level Shifter with DB9 Connector  (How To Install)  (Personally Tested) 
• Prototyping Jumer Wires (Male-to-Male | Female-to-Female | Male-to-Female)
• Solderless Breadboard
• John Jay's 8 LED & Button Breakout Board  (How To Build/Install)  (Personally Tested) 

Kits / Starter Packs

• CanaKit Raspberry Pi (512 MB) Complete Starter Kit
• Adafruit Raspberry Pi Starter Pack
• Adafruit Budget Pack for Raspberry Pi

RATINGS

I only rate items that I have personally used and or tested.

•  - Highest rating.  I really like it and use it regularly.
•   - Medium rating.  It's OK, there may be a more preferred option.
•  - Lowest rating.  I don't really like it and/or no longer use it regularly.

Also, please see the Quick Start Guide on the Raspberry Pi website:
http://www.raspberrypi.org/quick-start-guide

And the Getting Started post on this website

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

You can install multiple Java virtual machines (JVM) on your Raspberry Pi and switch between them as needed.  After installing the JVMs that you want, use the following command to select the default JVM/JRE.  

sudo update-alternatives --config java

With the new JVM selected, you can test and verify that is is the new default by  executing the java command using the version argument.

java -version

You should a response displaying the selected java version and VM:

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

I have recently been performing some benchmarks of the various Java Virtual Machines available on the Raspberry Pi ARM11 platform and thought I would share the results.  I used this test suite:  http://dacapobench.org/

Thanks to forum member chrisg on the Raspberry Pi forums who posted these benchmarks results for the previous Debian "Squeeze" image.  The results listed below for the OpenJDK are taken directly from chrisg's post.  I also ran these same tests on my Pi with Debian "Squeeze" and received very similar (maybe slightly higher) results.  

The following JVMs are represented:

• Oracle SE 7 JDK (7u6)
• Oracle SE 7 Embedded JRE (7u4) 
• OpenJDK Zero VM (6u18)
• OpenJDK Cacao VM (6u18)

The following chart includes all the tests performed and the resulting time in milliseconds that each test took to complete.  Obviously the lower number the better :-) 

I included a TOTAL line that sums up all the test results in minutes for each test case for rough comparisons, but please note that it does not compensate for the time missing from failed tests.

The test results are charted below for a visual representation.

I was particularly interested in the performance between the two available Oracle JVMs.  The results (as expected) were almost negligible.  The graph below illustrates the results of the two Oracle JVMs. 

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

The Oracle JDK for ARM is now available!  This article will provide the necessary instructions on how to install the Oracle Java Development Kit (JDK) on your Raspberry Pi.  

Prerequisites

• Install and boot the Raspberry Pi using the Debian "Wheezy" (2012-08-08 soft-float) image.  
  (The Oracle JDK is not currently compatible with the Raspian "Wheezy" image) 
• Enable the Raspberry Pi for SSH remote network connections.  
  Update:  The Debian "Wheezy" image comes with SSH access enabled in the default image.
  (Here is an article on how to enable SSH in the Debian Squeeze distribution)
• Get the Raspberry Pi's IP address.

Tools & Downloads:

All:

• Raspberry Pi Debian "Wheezy" image (2012-08-08)
• Oracle Java SE Development Kit (Select JDK Download, then Linux ARM - jdk-7u6-linux-arm-sfp.tar.gz)

Windows:

• WinSCP

Mac-OSX:

• Cyberduck

Download the Oracle JDK for the Raspberry Pi

You can download the Oracle Java SE Development Kit 7u6 on this page:
http://www.oracle.com/technetwork/java/javase/downloads/index.html

First, select JDK Download button under JDK SE 7, then select the LinuxARM JDK7 SE distribution (jdk-7u6-linux-arm-sfp.tar.gz). 

Transfer the Oracle JDK to the Raspberry Pi

After downloading the Oracle JDK to you desktop computer, we need to transfer it over to the Raspberry Pi.  We will use SCP to transfer the file over the network.  If you are running on a Windows desktop, then download and install WinSCP.

 If you are using Mac OSX, you can download and install Cyberduck.  The screens will look different but the goals are the same.

Create a new session in WinSCP using the IP address of you Raspberry Pi.  The default authentication credentials for the Debian Squeeze image is username "pi" and password "raspberry".  Save the session and then login.  You may be prompted to accept the SSH fingerprint, choose "Yes" to accept and continue.

After successfully establishing a connection, select the drive and folder location in the left pane where you download the Oracle JDK file to on your local desktop system.  In the right pane is the file system on the Raspberry Pi, we will leave it in it's default location in the "pi" user's home directory.  Drag and drop the Oracle JDK file from the left pane to the right pane and WinSCP will start the file transfer process.  You will be prompted with a transfer dialog, just click the "Copy" button to start the transfer.  

When the file transfer is complete, you can close WinSCP (or CyberDuck).

Installation Procedure on Raspberry Pi

The remaining steps should be performed directly on the console of the Raspberry Pi or using a SSH terminal connection with shell access.  In the last step, we transfered the Oracle JDK file to the "pi" user's home directory.  We should be logged in as the "pi" user and already in the user's home directory.

Lets create a new directory where we will install the JDK files to. 

sudo mkdir -p -v /opt/java

Next, lets unpack the Oracle JDK .gz file using this command

tar xvzf ~/jdk-7u6-linux-arm-sfp.gz

The unpacking process will take a few seconds to complete.  It unpacks all the contents of the Oracle JDK tz file to a new directory named "jdk1.7.0_06" located in the user's home directory.

With the unpack complete its now time to move the new unpacked directory to the Java install location that we created earlier under "opt/java".  

sudo mv -v ~/jdk1.7.0_06 /opt/java

We can also delete the original .tz file as it is no longer needed 

rm ~/jdk-7u6-linux-arm-sfp.gz

To complete the JDK installation we need to let the system know there is a new JVM installed and where it is located.  Use the following command to perform this task.

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/java/jdk1.7.0_06/bin/java" 1

And finally we also need to tell the system that we want this JDK to be the default Java runtime for the system. The following command will perform this action.

sudo update-alternatives --set java /opt/java/jdk1.7.0_06/bin/java

Now java is installed.  To test and verify we can execute the java command using the version argument.

java -version

You should get the following response:

That's it the Oracle JDK is installed and ready for use.

Add JAVA_HOME Environment Variable

Some Java programs require a JAVA_HOME environment variable to be configured on the system.  Add the following line to you "/etc/environment" using your favorite text editor.

JAVA_HOME="/opt/java/jdk1.7.0_06"

Also, edit your "~/.bashrc" file using this command

nano ~/.bashrc

and add the following two lines to the bottom of the file and save.

export JAVA_HOME="/opt/java/jdk1.7.0_06"
export PATH=$PATH:$JAVA_HOME/bin 

Reboot or re-login to apply the export to your environment.  

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

Attention

A new article has been posted that provides additional RS232 serial interface options, hardware, and wiring digrams.

• Raspberry Pi - RS232 Serial Interface Options (Revisit)

If you are trying to connect to a Raspberry Pi Compute Module Development board then see this article:

• RS232 Serial on Raspberry Pi Compute Module 

Do you need your Raspberry Pi to talk to serial controlled devices?  Do you need to access the Linux shell when you don't have a network connection and don't have the ability to connect the Pi to a keyboard and monitor?  Do you want to add more geek cred to your Pi by having a series of wires leads dangling from the GPIO header?  If the answer to any of these questions is YES!, then this is the post for you!  

Adding a RS232 serial port to the Raspberry Pi is actually quite simple.  Add you need is a RS-232 level shifter and a four wire leads to connect to the GPIO header.  So .. what a level shifter you ask.  A level shifter is a circuit that can take the low voltage (±3.3VDC) TTL signals for serial transmit (TX) and receive (RX) from the UART on the Pi and shift them to ±5VDC the voltage signals required for RS232 standard communication.  Want to know more?  Click here.     

There a many level shifters out there and the information here can be used to adapt any of them for you Raspberry Pi, but for wiring schematic and the illustrations used in this article I will focus on one that I had laying around the house available from XBit Electronics.

Xbit Electronics - RS-232 Level Shifter with DB9 Connector

Note:  The Xbit RS-232 level shifter is no longer available.  Any RS-232 level shifter that supports an input voltage down to 3 VDC should work juts fine.  Here are a couple of examples:

• Ableconn PI232DB9M Compact GPIO TX / RX to DB9M RS232 Serial Expansion Board for Raspberry Pi
• RS232 to TTL converter board DCE with Female DB9 3.3V to 5V

(click image to enlarge)

I used the following jumper wires to connect between the level-shifter and the Raspberry Pi GPIO header.  The Xbit level-shifter comes with a 5 pin header that you can solder directly on to the circuit board.  Mine is soldered on to the bottom of the level shifter so that I can insert it directly into the prototyping breadboard.  If you are not using a breadboard, then it is probably more convenient to solder the 5 pin header to the top of the Xbit circuit board.

I also used a prototyping breadboard to make my connections, but you could just as easily solder leads to the level-shifter if you want a more permanent solution.  Do not solder wires to the GPIO header, that is not a good idea.  Use either these prototype push pin connectors or a press-fit connect to interface with the GPIO header.  

(click image to enlarge)

This level-shifter uses a source supply (VCC) voltage of 3.3-5VDC.  Fortunately the Raspberry GPIO includes a pin that provide the 3.3 VDC neccessary for the VCC connection on the level-shifter.  The next three wiring connections are as simple as it gets ... Ground to Ground, TX to TX, and RX to RX.  A wiring diagram and close up photos are included below to help provide a clear picture of the connections.

(click any image to enlarge)

Here are a few alternatives to the XBit level shifter including an option without the DB9 connector and a USB option. 

• https://www.sparkfun.com/products/11189
• https://www.sparkfun.com/products/449
• https://www.sparkfun.com/products/718

(NOTE: I have not personally used or tested these alternative options but based on the specs they should work just fine.  Also when connecting a level shifter, please take note of the source voltage required to drive the level shifter.  Some are 5VDC only and other may support 3.3VDC.  Make sure to get one that support 3.3 VDC and connect it  to appropriate 3.3 VDC source voltage pin on the P1 header!)

Connecting to the Raspberry Pi Console

Both the Debian "Squeeze" and Raspian "Wheezy" images by default include support for accessing the shell by connecting a terminal emulation program to the serial port.  Just connect a straight thru serial cable (not a null modem cable) between the computer and your new DB9 port on your Raspberry Pi.  Open a terminal emulation software such as Hyperterminal, Procom Plus, or Indigo Terminal Emulator and connect to the serial port using settings "115200, N, 8, 1".   You may need to press the enter key a time or two to see the prompt.  Authenticate using your credentials and you are good to go.  

Enjoy the world of serial connectivity!

The Raspberry Pi is an inexpensive little ARM-based embedded computer developed as a teaching and experiment platform.  I wanted to experiment running Java applications on my Raspberry Pi so I need to install a Java Runtime to execute Java-based applications.  

I first installed the Open JDK on the device since this is the JRE flavor most commonly found in mainstream Linux OS distributions.   Installing the Open JDK is quite simple.  All you have to do is enter the following command and it will download and install the Open JDK.  

apt-get install openjdk-6-jdk

However, the performance I experienced while using the Open JDK on the Raspberry Pi was quite disappointing and dare I say unusable for any reasonably sophisticated Java program.  ChrisG posts some pretty revealing benchmarks using various JVMs in this blog article:  http://www.raspberrypi.org/phpBB3/viewtopic.php?f=34&t=6369   I ran the same benchmark tests on my Pi and got very similar results.  If you notice the Oracle JRE benchmark results in ChrisG's post you will see that they are an order of magnitude better in performance than the Open JDK Zero and Open JDK Cacao JVMs.  For my goals, this make the Oracle JVM the only suitable candidate for running my Java applications.  

This article will provide the necessary instructions on how to install the Oracle Java Runtime Environment on your Raspberry Pi.  

Prerequisites

• Install and boot the Raspberry Pi using the Debian "Wheezy" (2012-08-08 soft-float) image.  (or the older Debian "Squeeze" (2012-04-19) image) 
  (The Oracle JRE is not currently compatible with the Raspian "Wheezy" image) 
• Enable the Raspberry Pi for SSH remote network connections.  
  Update:  The Debian "Wheezy" image comes with SSH access enabled in the default image.
  (Here is an article on how to enable SSH in the Debian Squeeze distribution)
• Get the Raspberry Pi's IP address.

Tools & Downloads:

All:

• Raspberry Pi Debian "Wheezy" image (2012-08-08)
• Raspberry Pi Debian "Squeeze" image (2012-04-19)
• Oracle Java SE Embedded 7 (ARMv6/7 Linux - Headless - 1.7.0u4)

Windows:

• WinSCP

Mac-OSX:

• Cyberduck

Download the Oracle JRE for the Raspberry Pi

You can download the Oracle Java SE Embedded 7 JRE for ARMv6/7 Linux - Headless on this page:
http://www.oracle.com/technetwork/java/embedded/downloads/javase/index.html

Please note that you do unfortunately have to fill out a survey to download the JVM.  This means that you cannot simply use a tool such as wget or curl to download the JVM directly to the Raspberry Pi. (oracle-fail!)  Well I guess you could technically run "startx" and use a graphical browser in the X-Windows GUI to complete this step, but this article will use SCP to get the JVM file transferred to the Raspberry Pi.

Transfer the Oracle JRE to the Raspberry Pi

After downloading the Oracle JRE to you desktop computer, we need to transfer it over to the Raspberry Pi.  We will use SCP to transfer the file over the network.  If you are running on a Windows desktop, then download and install WinSCP.

 If you are using Mac OSX, you can download and install Cyberduck.  The screens will look different but the goals are the same.

Create a new session in WinSCP using the IP address of you Raspberry Pi.  The default authentication credentials for the Debian Squeeze image is username "pi" and password "raspberry".  Save the session and then login.  You may be prompted to accept the SSH fingerprint, choose "Yes" to accept and continue.

After successfully establishing a connection, select the drive and folder location in the left pane where you download the Oracle JRE file to on your local desktop system.  In the right pane is the file system on the Raspberry Pi, we will leave it in it's default location in the "pi" user's home directory.  Drag and drop the Oracle JRE file from the left pane to the right pane and WinSCP will start the file transfer process.  You will be prompted with a transfer dialog, just click the "Copy" button to start the transfer.  

When the file transfer is complete, you can close WinSCP (or CyberDuck).

Installation Procedure on Raspberry Pi

The remaining steps should be performed directly on the console of the Raspberry Pi or using a SSH terminal connection with shell access.  In the last step, we transfered the Oracle JRE file to the "pi" user's home directory.  We should be logged in as the "pi" user and already in the user's home directory.

Lets create a new directory where we will install the JRE files to. 

sudo mkdir -p -v /opt/java

Next, lets unpack the Oracle JRE tar file using this command

tar xvzf ~/ejre-7u4-fcs-b20-linux-arm-vfp-client_headless-12_apr_2012.gz

The unpacking process will take a few seconds to complete.  It unpacks all the contents of the Oracle JRE tar file to a new directory named "ejre1.7.0_04" located in the user's home directory.

With the unpack complete its now time to move the new unpacked directory to the Java install location that we created earlier under "opt/java".  

sudo mv -v ~/ejre1.7.0_04 /opt/java

We can also delete the original taf file as it is no longer needed 

rm ~/ejre-7u4-fcs-b20-linux-arm-vfp-client_headless-12_apr_2012.gz

To complete the JRE installation we need to let the system know there is a new JVM installed and where it is located.  Use the following command to perform this task.

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/java/ejre1.7.0_04/bin/java" 1

And finally we also need to tell the system that we want this JRE to be the default JRE for the system. The following command will perform this action.

sudo update-alternatives --set java /opt/java/ejre1.7.0_04/bin/java

Now java is installed.  To test and verify we can execute the java command using the version argument.

java -version

You should get the following response:

That's it the Oracle JRE is installed and ready for use.

Add JAVA_HOME Environment Variable

Some Java programs require a JAVA_HOME environment variable to be configured on the system.  Add the following line to you "/etc/environment" or your "~/.bashrc" file using your favorite text editor.

JAVA_HOME="/opt/java/ejre1.7.0_04"

Reboot or re-login to apply the export to your environment.  

Coffee & Pie  - what could be better!  

Demo Video 

Hinkmond Wong and Gary Collins of Oracle are going to introduce you to developing for the Raspberry Pi using Java Embedded technology.

In addition to demoing the Raspberry Pi running Java Embedded, they will cover:

• What is Java SE Embedded?
• Developing with Java for Embedded
• Best practices w/ Java for Embedded 
• Downloading and installing Java SE Embedded Platform

* Raspberry Pi is a trademark of the Raspberry Pi foundation.
* Oracle and Java are registered trademarks of Oracle.

For some applications you may not want your Raspberry Pi permanenenty attached to a monitor and keyboard or perhaps you just would like to be able to access your Raspberry Pi remotely.  Enabling the SSH server on your Raspberry Pi will provide SSH terminal access over your network.  This article will cover the steps need to enable the SSH server for remote access and how to connect to the Raspberry Pi using a SSH terminal enumation software from Windows and Mac OSX.  

Enable SSH Server on Raspberry Pi    

NOTE:  

If you are running the Raspian "Wheezy" image or the Debian "Wheezy" image, please note that SSH is already enabled by default.  You can also use the Raspberry configuration utility to enable/disable the SSH server by running the command and selecting the SSH item from the menu: 

sudo raspi-config 

 

You can skip this section and proceed to the next section in the article.

From the console on the Raspberry Pi please enter the following two commands:

sudo rm /etc/ssh/ssh_host_*
sudo dpkg-reconfigure openssh-server

These steps will create the RSA and DSA encryption keys enable the SSH server.  The SSH server will also be started automatically each time you reboot your Raspberry Pi.  

Now, lets get connected.

Getting the IP Adrress from your Raspberry Pi    

Before we can connect remotely, we first need to determine what the IP address is for the Raspberry Pi.  For most users, when the Raspberry Pi boots up and is connected to you router/switch/residential gateway it will dynamically obtain an IP address using DHCP.  

Use the following command from the console to get the IP adress:

ifconfig

In the resulting output on the screen, look for the inet add for the eth0 device.

Connect from Windows

You can use any terminal emulation software you like; however, for this demonstration we will use Putty a very popular an free terminal software for Windows.

You can download the Putty software here.

Double click the putty.exe program to start Putty.  You will be prompted with the Putty configuration dialog.  Enter the IP address of your Raspberry Pi in the Host Name field and make sure the the connection type is set to SSH.  

To persist these setting so you don't have to re-enter them every time you start Putty, enter a name such as "RaspberyrPi" in the Saved Sessions field and press the Save button.

Click the Open button to connect to the Raspberry Pi and start the SSH session.
You will be prompted with a message to cache the RSA2 fingerprint.  Select Yes to accept the key and continue the connection. 

Upon connection, you will need to provide the authentication credentials to logon to the Raspberry Pi. 
The credentials may vary depending on the operating system image that you installed on your Raspberry.  If you loaded Raspian "Wheezy" or Debian "Squeeze" then use username "pi" and password "raspberry".    

Now you can interact with your Raspberry Pi just as if you where setting at the keyboard console.  

Connect from Mac OSX

No additional software is needed for OSX to connect to the Raspberry SSH server.  Just open theTerminal application and enter the ssh command with the username@ip-address format:

ssh pi@10.1.1.194

Upon connection, you will need to provide the authentication credentials to logon to the Raspberry Pi.  The credentials may vary depending on the operating system image that you installed on your Raspberry.  If you loaded Raspian "Wheezy" or Debian "Squeeze" then use username "pi" and password "raspberry".   

Now you can interact with your Raspberry Pi just as if you where setting at the keyboard console.  

The Raspberry Pi is a revolutionary step forward in bringing low cost embedded computing to the masses.  Designed as an educational learning tool and the "B" model priced at only $35 USD, the Raspberry Pi makes a great little device for DIYers and hobbyists. 

This article will provide the necessary information on the basic supplies needed and instructions on getting started with your new Raspberry Pi.   

Supplies

• Raspberry Pi - Model B
• SDHC Card (4 GB or more; Preferably Class 10)
• Micro USB Cable
• Power Supply (5 volt with at least 700mA)
• HDMI Cable
• USB Keyboard
• USB Mouse
• Ethernet Cable (optional)
• Case / Enclosure (optional)

A shopping list with direct linked items is available via this post.

Power

To power the Raspberry Pi you will need a 5 VDC power supply with a minimum of 700 mA and micro USB connector to plug into the micros USB port on the board.  

If you have an extra Apple iPhone charger laying around, this makes a perfect power supply for the Raspberry Pi.  The Apple iPhone charger is 5VDC @ 1A (1000mA).  Using the Apple iPhone charger or similar USB charger you will still need a USB to micro USB adapter (A Male to Micro B).  I used this AmazonBasics USB Cable - 2.0 A Male to Micro B (6 Feet / 1.8 Meters)

NOTE:  
Do not attempt to use your computer's USB port to power the Raspberry Pi.

Video/Display

The Raspberry Pi includes a HDMI port to connect the device to a computer or TV monitor.  If you monitor does not accept a HDMI connection directly, then you many need a HDMI to DVI or HDMI to display port adapter/cable.  I am using this HDMI/DVI adapter cable that I picked up from Amazon:  Eforcity Black 6FT /2 Meter HDMI Male to DVI Male Cable  

Keyboard/Mouse

You can plug in just about any standard USB keyboard and mouse.  I am using a USB to PS2 adapter with an old PS2 keyboard and PS2 mouse. 

Network Connectivity

You will need a network (CAT-5) ethernet cable to connect the Raspberry Pi to you network switch/hub/router/residential gateway.

Installing OS Image

Before booting your Raspberry Pi for the first time, you will need to flash an operating system to a SD card using a Windows, Apple Mac. or other Linux computer with an SD card reader.  You can download your choice of operating system image from the main Raspberry Pi download page:
http://www.raspberrypi.org/downloads 

Or from the Raspberry Pi Wiki distributions page:
http://elinux.org/RaspberryPiBoardDistributions

The following page includes detailed instructions based on your desktop operating system for flashing the image to the SD card.
http://elinux.org/RPi_Easy_SD_Card_Setup 

Once your SD card has been flashed successfully, you are ready to insert it into the Raspberry Pi and boot it up.

NOTE:  If you are planning on running Java-based applications and want to run using the Oracle JRE, then you should use the "Debian ARM 2012-04-19 (Squeeze)" distribution at this time instead of the newer "2012-08-07 (raspbian/wheezy)" distribution.  The newer distribution supports hardware floating point, but is incompatible with the Oracle JRE at this time. 

Booting & Initial Configuration

On inital boot, depending on the image you load, the Raspberry Pi may reboot one or more times while setting itself up.  Once complete a login prompt should be provided allowing you to enter credentials to access the console.  The login credentials vary depending on which distribution you have loaded, but the default credentials for Raspbian and Debian distributions are username "pi" and password "raspberry".

If you are using the Raspbian "Wheezy" image, the raspi-config configuration utility should load on the first boot and allow you to select your local configuration options.

If you are using the Debian "Squeeze" image, you will need to run the following commands to configure the system your your locale, keyboard and timezone.

sudo dpkg-reconfigure locales
sudo dpkg-reconfigure keyboard-configuration
sudo dpkg-reconfigure tzdata 

For information on other distributions, please see this page:  http://elinux.org/RaspberryPiBoardDistributions

Starting X (GUI)

Run the following command from the console to start the graphical user interface.

startx

Now you are up and running .. have fun with your Raspberry Pi! 

* Raspberry Pi is a trademark of the Raspberry Pi foundation.