Pi4 GPIO Control with Java

Question

I am basically trying to turn on a led by using pi4j library. My code is pretty simple:

public static void main(String args[]) throws InterruptedException {
    GpioController gpioController = GpioFactory.getInstance();
    GpioPinDigitalOutput pinOut = gpioController.provisionDigitalOutputPin(RaspiPin.GPIO_17);
    pinOut.high();
    Thread.sleep(5000);
    pinOut.low();
}

I am exporting the jar file from my computer, copying to my Raspberry Pi 4 than running in there.

To check if my led is not broken or GPIO is set, I've executed following Python scripts and I see my led works perfectly:

python
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)
GPIO.output(17,True)

What am I missing?

score 1 · Accepted Answer · answered Oct 12 '20 at 06:51

Indeed as mentioned in the comments, Pi4J is using a different pin numbering scheme. "Under the hood", WiringPi is used to control the GPIOs. This library uses a different numbering scheme. This means BCM pin 17 you are using in Python is pin 0 in the WiringPi scheme.

See below a full table with BCM, WiringPi, and physical pin numbering (see link 2 below).

Next to that, the internal wiring of the Raspberry Pi 4 is different compared to the previous ones, so you'll need to upgrade your WiringPi to the latest version 2.52 with:

$ gpio -v
gpio version: 2.50
$ cd /tmp
$ wget https://project-downloads.drogon.net/wiringpi-latest.deb
$ sudo dpkg -i wiringpi-latest.deb
$ gpio -v
gpio version: 2.52

As a side note: we are working on a new version of Pi4J which will make things easiers, but work-in-progress... ;-)

Pi4 GPIO Control with Java

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