[CON3189] JavaOne 2016 - Introduction to Java ME development for the Raspberry Pi

Introduction to Java ME
for the Raspberry Pi
[JavaOne 2016 CON3189]
Kevin Hooke
Julio Palma Vazquez

Who Are We?
Copyright © 2016 Accenture All rights reserved.
Kevin Hooke
Technology Architect
Accenture Java Community Champion
@kevinhooke
Julio Palma
Technology Architect
Accenture Java Community Champion
@restalion

Related Sessions JavaOne 2016
Monday, Sep 19 Tuesday, Sep 20 Wednesday, Sep 21
Introduction to Java ME 8
[CON3189]
Java ME and Single-Board
Computers for Creating
Industrial
Middleware [CON3187]
All Your Faces Belong to Us:
Building an Open Face
Recognition Platform
[CON6217]
12:30 p.m. - 1:30 p.m 2:30 p.m. - 3:30 p.m 3:00 p.m. - 4:00 p.m
Hilton - Golden Gate 6/7/8 Hilton - Golden Gate 6/7/8 Hilton - Golden Gate 6/7/8
Kevin Hooke
Julio Palma
Jorge Hidalgo
Julio Palma
Jorge Hidalgo
Mariano Rodriguez

Session Goals
Java ME SDK + IDE Plugins+
+
+
By Afrank99 - Own work, CC BY-SA 2.0,
https://commons.wikimedia.org/w/index.php?curid=227264
By Inductiveload - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=8385509

Session Goals
Java ME SDK + IDE Plugins+
+
+
By Inductiveload - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=8385509
Build one of these:

Getting Started: Required Setup
Dev tools:
• Java ME SDK 8.3 (for Window or Linux)
• NetBeans 8.1 (Or Eclipse)
• NetBeans Java ME SDK 8.3 plugins (Or Eclipse)
Raspberry Pi runtime:
• Raspberry Pi (although can develop with emulator in ME SDK)
• Raspbian
• Java ME Embedded 8.3 for Raspberry Pi

NetBeans setup
• Tools / Plugins /
Settings tab, Add new
‘Update Center’
• Point to unzipped
Java ME SDK plugins
in a dir using file://
On Windows:
• Use file:///
• path to folder with no
spaces in name works
best)

NetBeans setup (2)
• ‘Available plugins’
tab
• Select:
• Java ME SDK
Tools
• Java ME SDK
Demos
• Press Install
• Ok and restart
NetBeans when
prompted

NetBeans setup (3)
• ME SDK Welcome
displayed on restart:

Creating a new ME Project
• File / New Project / Java
ME Embedded

Creating a new ME project (2)
• Defaults will use an emulated
Embedded Device
• Emulated devices and connections to
real hardware provided by Java ME
SDK Device Manager (Windows and
Linux)

Raspberry Pi setup
• SCP/SFTP Java ME JDK zip for Raspberry Pi to your Pi
• Unzip, cd to bin
• ./fix_permissions.sh
• Run with: sudo ./usertest.sh

Connect Device Manager to Java ME on Pi
• Press ‘+’ in Device Connection Manager
• If connected over network, give IP of the
remote Pi (might auto detect)
• Should see connection status listed as
connected (below):

Publish project to Pi
• Change Project Properties on Project
• Select ‘Platform’
• Change ‘Device’ to newly added Raspberry Pi

Java ME Hello World!
• Instead of a simple (typical)
System.out.println()
• Internet of Things (IoT) and
embedded devices are all about
hardware
• Let’s say ‘Hello World’ with a
flashing LED!
• First need to understand
available GPIO pins on the Pi

Raspberry Pi GPIO pins
• Pins for Input and Output – 3.3v
• For interacting with external devices:
switches, LEDs, sensors etc
• Building blocks for building IoT type
solutions!
From: Herbfargus - Own work, CC BY-SA 4.0,

Raspberry Pi GPIO pins(2)
• What pin does what? (not all are GPIO)
• Raspberry Pi docs site shows which pins are power/ground, and GPIO
• Interactive online diagrams, like https://pinout.xyz/
From: https://www.raspberrypi.org/documentation/usage/gpio-plus-and-
raspi2/README.md

Java ME and GPIO Pins
DeviceManager.open(int)
• refers to GPIO pin by Device Id (NOT GPIO pin number)
• e.g. 1 == GPIO4
• See mappings in docs here:
http://docs.oracle.com/javame/8.3/get-started-rpi/device-i-o-preconfigured-
list.htm#MEEPG148

Java ME and GPIO Pins
DeviceManager.open(int)
• refers to GPIO pin by Device Id (NOT GPIO pin number)
• e.g. 1 == GPIO4
• See mappings in docs here:
http://docs.oracle.com/javame/8.3/get-started-rpi/device-i-o-preconfigured-
list.htm#MEEPG148
Less confusing – open by “pin name”, e.g. “GPIO4”
DeviceManager.open(“GPIO4”, GPIOPin.class)
• Refers to pin by configured name, e.g. “GPIO4”.
• Mappings defined in same doc above

Java ME Preconfigured Pin example
From: http://docs.oracle.com/javame/8.3/get-started-rpi/device-i-o-preconfigured-
list.htm#MEEPG148
Device Id
Pin name

Java ME Hello World – Flashing LED!
GPIOPin pin18 = DeviceManager.open(“GPIO18”, GPIOPin.class);
boolean currentValue = false;
while(true){
currentValue = !currentValue;
pin18.setValue(currentValue);
System.out.println("Changing pin value to: " + currentValue);
Thread.sleep(2000);
}

Progress so far
Pin18.setValue(true);
+
We can now turn on/off LEDs!

Raspberry Pi Emulator Device
• Allows for local testing
• Use a preconfigured emulator device that represents pins on actual device:
https://github.com/SubOptimal/RaspberryPI_EmulatorDevice
• Download zip
• From Java ME Tools in NetBeans, select “Custom Device Emulator”
• Click Import, point to downloaded zip

Raspberry Pi Emulated Device (2)
• Now see
RaspberryPi_EmulatorDevice
in Device Selector list
• By default – does not include
libraries, need to select in
config too

Raspberry Pi Emulated Device (3)
In Custom Device Editor, Edit – add required libraries for your project
e.g. Device I/O Api – Access and Control (DeviceManager api) and GPIO (for GPIO pins
api)

Java ME API Security Permissions
• Deploying first app, you’ll likely see this error (if you’re not following a tutorial):

Java ME API Security Permissions (2)
• Select View / Device Log: “Permission check failed”
This indicates API
permissions are missing
You need to set Permissions
to access resources on the
device
From Project Properties /
Application Descriptor:

Java ME API Security Permissions (3)
• Click Add – add open permission for each GPIO pin you need to control (or wildcard *:*):

ME device id vs GPIO pin number error
Error:
jdk.dio.DeviceNotFoundException: Device 14 not found
- jdk/dio/DeviceManager.open(), bci=87
Check:
Are you trying to use GPIO pins ids, and not Device Ids?
e.g.
DeviceManager.open(14)
(there is no DeviceId == 14)

Configuring GPIO pins & creating Event Listeners
• To handle button clicks (button click = event)
• Configure pin for input, and register a listener:
GPIOPin gpio4 = DeviceManager.open(new GPIOPinConfig.Builder()
.setPinNumber(GPIO4_pin)
.setDirection(GPIOPinConfig.DIR_INPUT_ONLY)
.setTrigger(GPIOPinConfig.TRIGGER_FALLING_EDGE)
.build());
gpio4.setInputListener((PinListener) this);

Event Listeners (2)
• Implement the PinListener interface:
public class JavaMETestButton extends MIDlet implements PinListener {
// …
public void valueChanged(PinEvent event) {
//do something here!
System.out.println("gpio4 event/button press!");
}

Default Java ME defined pin mappings
DIR_INPUT_ONLY
• GPIO4
• GPIO17
• GPIO22
• GPIO27
DIR_OUTPUT_ONLY
• GPIO7
• GPIO18
• GPIO23
• GPIO24
• GPIO25
Pre-configured / default
pins:

Progress so far (2)
• You can now:
–Write code to interact with the physical world!
–Turn on/off pins - turn on LEDs/Lights, trigger relays
–Detect high/low on a pin - react to switch/button/sensor

Progress so far (3)
https://commons.wikimedia.org/w/index.php?curid
=227264
pin18.setValue(true);
+
By Inductiveload - Own work, Public Domain,
385509
+
GPIOPin gpio4 = DeviceManager.open(new GPIOPinConfig.Builder()
.setPinNumber(GPIO4_pin)
.setDirection(GPIOPinConfig.DIR_INPUT_ONLY)
.setTrigger(GPIOPinConfig.TRIGGER_FALLING_EDGE)
.build());
gpio4.setInputListener((PinListener) this);
Basic building blocks for any embedded project!

Demos!

Demo Source
https://github.com/kevinhooke/JavaMESimpleLEDTest
https://github.com/kevinhooke/RaspPiLEDsAndButtonsGame

Downloads & Useful Links
https://www.raspberrypi.org
https://netbeans.org/
http://www.oracle.com/technetwork/java/embedded/javame/javame-
sdk/downloads/javamesdkdownloads-2166598.html

[CON3189] JavaOne 2016 - Introduction to Java ME development for the Raspberry Pi

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