public static void main(String[] args) throws InterruptedException {
// START SNIPPET: usage-create-controller-snippet
// create gpio controller instance
final GpioController gpio = GpioFactory.getInstance();
// END SNIPPET: usage-create-controller-snippet
// START SNIPPET: usage-provision-input-pin-snippet
// provision gpio pin #02 as an input pin with its internal pull down resistor enabled
// (configure pin edge to both rising and falling to get notified for HIGH and LOW state
// changes)
GpioPinDigitalInput myButton =
gpio.provisionDigitalInputPin(
RaspiPin.GPIO_02, // PIN NUMBER
"MyButton", // PIN FRIENDLY NAME (optional)
PinPullResistance.PULL_DOWN); // PIN RESISTANCE (optional)
// END SNIPPET: usage-provision-input-pin-snippet
// START SNIPPET: usage-provision-output-pin-snippet
// provision gpio pins #04 as an output pin and make sure is is set to LOW at startup
GpioPinDigitalOutput myLed =
gpio.provisionDigitalOutputPin(
RaspiPin.GPIO_04, // PIN NUMBER
"My LED", // PIN FRIENDLY NAME (optional)
PinState.LOW); // PIN STARTUP STATE (optional)
// END SNIPPET: usage-provision-output-pin-snippet
// START SNIPPET: usage-shutdown-pin-snippet
// configure the pin shutdown behavior; these settings will be
// automatically applied to the pin when the application is terminated
// ensure that the LED is turned OFF when the application is shutdown
myLed.setShutdownOptions(true, PinState.LOW, PinPullResistance.OFF);
// END SNIPPET: usage-shutdown-pin-snippet
// START SNIPPET: usage-control-pin-snippet
// explicitly set a state on the pin object
myLed.setState(PinState.HIGH);
// use convenience wrapper method to set state on the pin object
myLed.low();
myLed.high();
// use toggle method to apply inverse state on the pin object
myLed.toggle();
// use pulse method to set the pin to the HIGH state for
// an explicit length of time in milliseconds
myLed.pulse(1000);
// END SNIPPET: usage-control-pin-snippet
// START SNIPPET: usage-read-pin-snippet
// get explicit state enumeration for the GPIO pin associated with the button
PinState myButtonState = myButton.getState();
// use convenience wrapper method to interrogate the button state
boolean buttonPressed = myButton.isHigh();
// END SNIPPET: usage-read-pin-snippet
// START SNIPPET: usage-register-listener-snippet
// create and register gpio pin listener
myButton.addListener(new GpioUsageExampleListener());
// END SNIPPET: usage-register-listener-snippet
// START SNIPPET: usage-trigger-snippet
// create a gpio synchronization trigger on the input pin
// when the input state changes, also set LED controlling gpio pin to same state
myButton.addTrigger(new GpioSyncStateTrigger(myLed));
// END SNIPPET: usage-trigger-snippet
// keep program running until user aborts (CTRL-C)
while (true) {
Thread.sleep(500);
}
// stop all GPIO activity/threads by shutting down the GPIO controller
// (this method will forcefully shutdown all GPIO monitoring threads and scheduled tasks)
// gpio.shutdown(); <--- implement this method call if you wish to terminate the Pi4J GPIO
// controller
}
/**
* [ARGUMENT/OPTION "--pin (#)" | "-p (#)" ] This example program accepts an optional argument for
* specifying the GPIO pin (by number) to use with this GPIO listener example. If no argument is
* provided, then GPIO #1 will be used. -- EXAMPLE: "--pin 4" or "-p 0".
*
* <p>[ARGUMENT/OPTION "--pull (up|down|off)" | "-l (up|down|off)" | "--up" | "--down" ] This
* example program accepts an optional argument for specifying pin pull resistance. Supported
* values: "up|down" (or simply "1|0"). If no value is specified in the command argument, then the
* pin pull resistance will be set to PULL_UP by default. -- EXAMPLES: "--pull up", "-pull down",
* "--pull off", "--up", "--down", "-pull 0", "--pull 1", "-l up", "-l down".
*
* @param args
* @throws InterruptedException
* @throws PlatformAlreadyAssignedException
*/
public static void main(String[] args)
throws InterruptedException, PlatformAlreadyAssignedException {
// ####################################################################
//
// since we are not using the default Raspberry Pi platform, we should
// explicitly assign the platform as the BananaPro platform.
//
// ####################################################################
PlatformManager.setPlatform(Platform.BANANAPRO);
// create Pi4J console wrapper/helper
// (This is a utility class to abstract some of the boilerplate code)
final Console console = new Console();
// print program title/header
console.title("<-- The Pi4J Project -->", "GPIO Input Example");
// allow for user to exit program using CTRL-C
console.promptForExit();
// create gpio controller
final GpioController gpio = GpioFactory.getInstance();
// ####################################################################
//
// When provisioning a pin, use the BananaProPin class.
//
// ####################################################################
// by default we will use gpio pin #01; however, if an argument
// has been provided, then lookup the pin by address
Pin pin =
CommandArgumentParser.getPin(
BananaProPin.class, // pin provider class to obtain pin instance from
BananaProPin.GPIO_01, // default pin if no pin argument found
args); // argument array to search in
// by default we will use gpio pin PULL-UP; however, if an argument
// has been provided, then use the specified pull resistance
PinPullResistance pull =
CommandArgumentParser.getPinPullResistance(
PinPullResistance.PULL_UP, // default pin pull resistance if no pull argument found
args); // argument array to search in
// provision gpio pin as an input pin
final GpioPinDigitalInput input = gpio.provisionDigitalInputPin(pin, "MyInput", pull);
// set shutdown state for this pin: unexport the pin
input.setShutdownOptions(true);
// prompt user that we are ready
console.println("Successfully provisioned [" + pin + "] with PULL resistance = [" + pull + "]");
console.emptyLine();
console.box("The GPIO input pin states will be displayed below.");
console.emptyLine();
// display pin state
console.emptyLine();
console.println(
" ["
+ input.toString()
+ "] digital state is: "
+ ConsoleColor.conditional(
input.getState().isHigh(), // conditional expression
ConsoleColor.GREEN, // positive conditional color
ConsoleColor.RED, // negative conditional color
input.getState()));
console.emptyLine();
// stop all GPIO activity/threads by shutting down the GPIO controller
// (this method will forcefully shutdown all GPIO monitoring threads and scheduled tasks)
gpio.shutdown();
}
