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Pi4J V2 :: CrowPi Examples

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This project contains both example applications and ready-made component classes for interacting with the CrowPi using the Pi4J (V2) library. You can easily get started with electronics programming by testing and modifying the bundled examples or even write your own application.


The provided component classes as part of this library provide an implementation for every available component of the CrowPi. The following table provides an overview of all supported components with a link to their implementation and example app:

Component Example App Implementation
Humidity/Temperature Sensor
IR Receiver
LCD Display
LED Matrix
Light Sensor
PIR Motion Sensor
Servo Motor
Seven Segment Display
Step Motor
Tilt Sensor
Touch Sensor
Ultrasonic Distance Sensor
Vibration Motor

Due to very tight timing constraints, two of the components had to use an alternative implementation without relying on Java. This could be improved in the future by moving this logic into native code using JNI or putting these components behind a dedicated microcontroller:

  • IR Receiver: This component relies on the mode2 binary for retrieving the signal pulses, provided as part of the LIRC software bundle. While all parsing and logic has been implemented in Java, measuring the pulses accurately enough was not possible.
  • Humidity/Temperature Sensor: Due to being based on a DHT11 sensor, this component requires an extreme amount of precision in terms of timing, resulting in measurement failures even when running as native code on a Raspberry Pi. To still provide some support for this component, it requires setting up the dht11 kernel module which is part of Linux Industrial I/O.

The CrowPi OS image mentioned further down below supports both workarounds out of the box without further configuration.


The Pi4J-team provides several pre-built custom OS images. It's highly recommended to use the so called CrowPi OS for your CrowPi experiments to get the following set of benefits:

  • Preconfigured locale (en_US), keyboard (US) and timezone (Europe/Zurich)
  • Preconfigured wireless country (Switzerland) by default
  • Remote management via SSH and VNC possible without configuration
  • Preinstalled OpenJDK 17 and JavaFX to get quickly started
  • Preconfigured /boot/config.txt which supports all components out of the box
  • Dynamic wallpaper which shows Ethernet/WLAN address and hostname
  • Comes with lirc preinstalled to run the IR receiver component

Download the latest zip-compressed archive, extract it and flash it with the imaging tool of your choice to get started. The default installation provides an user account pi with the password crowpi and sudo privileges.


To simplify adding and launching new applications, a custom launcher has been built using PicoCLI. The class contains a static list of available targets called APPLICATIONS which has to be adjusted when adding new applications to the project.

By default, an interactive menu gets shown which allows selecting a single target to launch. After executing this target, the application will automatically end. You may optionally specify the name of an application as the first argument, i.e. BuzzerApp, to directly launch this specific application.

If you want to comfortably test all supported components at once, you may specify the flag --demo which will return to the interactive launcher menu once a target has been executed.

Creating your own applications is as simple as implementing the provided interface, which only requires a single void execute(Context pi4j) method.


This project uses Maven for building, testing and running the various applications. While it can be used directly on a Raspberry Pi / CrowPi, it also supports compiling everything together locally, then pushing the artifacts to the device and running them remotely. The build system defaults to local deployments, but the following set of Maven properties can be set for remote deployments:

  • (required): Current IP address of the CrowPi, e.g., used for SCP/SSH
  • crowpi.remote.port (optional): Port to use for SCP/SSH communication, defaults to 22
  • crowpi.remote.username (optional): Username to use for SCP/SSH, defaults to pi
  • crowpi.remote.password (optional): Password to use for SCP/SSH, defaults to crowpi
  • (optional): Default directory to temporarily store built artifacts, defaults to /home/pi/deploy
  • crowpi.remote.jvmOptions (optional): Additional JVM options, defaults to an empty string

In case of a remote deployment, the artifacts get pushed via SCP and will be automatically executed using SSH. Please note that any existing files in the deployment folder are being automatically overwritten.

Regardless of which deployment mode you have chosen, the property crowpi.launcher.args can be set to specify which arguments should be passed as-is when running the launcher. This can be used for launching demo mode or directly executing a single application.


You may skip this section when using the pre-built CrowPi OS image. Should you choose to run your own image instead, you will need to ensure that the following lines are present in your /boot/config.txt:

# Enable X with 128MB GPU memory and support the custom resolution of the CrowPi LCD panel
start_x = 1
gpu_mem = 128
hdmi_cvt 1024 600 60 6 0 0 0

# Enable I2C and SPI
dtparam = i2c_arm=on
dtparam = spi=on

# Enable audio
dtparam = audio=on

# Enable GPIO-IR
dtoverlay = gpio-ir,gpio_pin=20

# Enable DHT11
dtoverlay = dht11,gpiopin=4

# Enable DRM VC4 V3D with up to 2 frame buffers
dtoverlay = vc4-fkms-v3d
max_framebuffers = 2

If you want to use the IR receiver and/or humidity/temperature sensor component, you will have to ensure that the required dependencies mentioned in the "COMPONENTS" section of this README have also been fulfilled.


This project has the following runtime dependency requirements:


$ git clone
$ cd pi4j-example-crowpi
$ mvn package
$ cd target/distribution/
$ sudo java --module-path . --module com.pi4j.crowpi/com.pi4j.crowpi.Launcher $@

> No application has been specified, defaulting to interactive selection
> Run this launcher with --help for further information
[main] INFO com.pi4j.Pi4J - New context builder
[main] INFO com.pi4j.platform.impl.DefaultRuntimePlatforms - adding platform to managed platform map [id=raspberrypi; name=RaspberryPi Platform; priority=5; class=com.pi4j.crowpi.helpers.CrowPiPlatform]
> The following launch targets are available:
1) Exit launcher without running application
2) ButtonApp (com.pi4j.crowpi.applications.ButtonApp)
3) ButtonMatrixApp (com.pi4j.crowpi.applications.ButtonMatrixApp)
4) BuzzerApp (com.pi4j.crowpi.applications.BuzzerApp)
5) ExampleApp (com.pi4j.crowpi.applications.ExampleApp)
6) HumiTempApp (com.pi4j.crowpi.applications.HumiTempApp)
7) IrReceiverApp (com.pi4j.crowpi.applications.IrReceiverApp)
8) LcdDisplayApp (com.pi4j.crowpi.applications.LcdDisplayApp)
9) LedMatrixApp (com.pi4j.crowpi.applications.LedMatrixApp)
10) LightSensorApp (com.pi4j.crowpi.applications.LightSensorApp)
11) RfidApp (com.pi4j.crowpi.applications.RfidApp)
12) PirMotionSensorApp (com.pi4j.crowpi.applications.PirMotionSensorApp)
13) RelayApp (com.pi4j.crowpi.applications.RelayApp)
14) ServoMotorApp (com.pi4j.crowpi.applications.ServoMotorApp)
15) SevenSegmentApp (com.pi4j.crowpi.applications.SevenSegmentApp)
16) SoundSensorApp (com.pi4j.crowpi.applications.SoundSensorApp)
17) StepMotorApp (com.pi4j.crowpi.applications.StepMotorApp)
18) TiltSensorApp (com.pi4j.crowpi.applications.TiltSensorApp)
19) TouchSensorApp (com.pi4j.crowpi.applications.TouchSensorApp)
20) UltrasonicDistanceSensorApp (com.pi4j.crowpi.applications.UltrasonicDistanceSensorApp)
21) VibrationMotorApp (com.pi4j.crowpi.applications.VibrationMotorApp)
> Please choose your desired launch target by typing its number:


This repository is licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at:

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


Pi4J V2 example which introduces you to electronics programming with Java on the Raspberry Pi and CrowPi







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