PI 2 - GPIO pin stays HIGH even when I toggle ( in Java)

Question

Hi my first Java program to control a LED has failed, the LED does not come on even though the pin state is continuously HIGH ?

Heres the Java code :-

final GpioController gpio = GpioFactory.getInstance();
System.out.println("Setting GPIO_04 as output");
final GpioPinDigitalOutput led = gpio.provisionDigitalOutputPin( RaspiPin.GPIO_04 );
boolean currentState = false;
for (;;) {
    Thread.sleep( 1000 );
    System.out.println("Current state is " + led.getState());
    led.toggle();
}

This prints out :-

Setting the GPIO_04 as output
Current state is HIGH
Current state is HIGH
Current state is HIGH

etc... ?? What am I doing wrong ? why is the state continuously HIGH and why isnt the LED on ? (It comes on if I connect to the 5v or 3.3v pins so the circuit is ok)

Answer 1

Did you use the correct pins? There is a difference between the old Rev1 and Rev2 GPIO layout so you might used a wrong reference.

If you plan to do loads of led GPIO, the time to designa GPIO LED overview board might save you a lot of time in the future.

A good reference for pin layouts is http://wiringpi.com/pins/ However actual GPIO numbers might differ depending on which lib you're using.