package com.pi4j.example;
import com.pi4j.Pi4J;
import com.pi4j.io.gpio.digital.DigitalInput;
import com.pi4j.io.gpio.digital.DigitalOutput;
import com.pi4j.io.gpio.digital.DigitalState;
import com.pi4j.io.gpio.digital.PullResistance;
import com.pi4j.util.Console;
/**
* <p>This example fully describes the base usage of Pi4J by providing extensive comments in each step.</p>
*
* @author Frank Delporte (<a href="https://www.webtechie.be">https://www.webtechie.be</a>)
* @version $Id: $Id
*/
public class MinimalExample {
private static final int PIN_BUTTON = 24; // PIN 18 = BCM 24
private static final int PIN_LED = 22; // PIN 15 = BCM 22
private static int pressCount = 0;
/**
* This application blinks a led and counts the number the button is pressed. The blink speed increases with each
* button press, and after 5 presses the application finishes.
*
* @param args an array of {@link java.lang.String} objects.
* @throws java.lang.Exception if any.
*/
public static void main(String[] args) throws Exception {
// Create Pi4J console wrapper/helper
// (This is a utility class to abstract some of the boilerplate stdin/stdout code)
final var console = new Console();
// Print program title/header
console.title("<-- The Pi4J Project -->", "Minimal Example project");
// ************************************************************
//
// WELCOME TO Pi4J:
//
// Here we will use this getting started example to
// demonstrate the basic fundamentals of the Pi4J library.
//
// This example is to introduce you to the boilerplate
// logic and concepts required for all applications using
// the Pi4J library. This example will do use some basic I/O.
// Check the pi4j-examples project to learn about all the I/O
// functions of Pi4J.
//
// ************************************************************
// ------------------------------------------------------------
// Initialize the Pi4J Runtime Context
// ------------------------------------------------------------
// Before you can use Pi4J you must initialize a new runtime
// context.
//
// The 'Pi4J' static class includes a few helper context
// creators for the most common use cases. The 'newAutoContext()'
// method will automatically load all available Pi4J
// extensions found in the application's classpath which
// may include 'Platforms' and 'I/O Providers'
var pi4j = Pi4J.newAutoContext();
// ------------------------------------------------------------
// Output Pi4J Context information
// ------------------------------------------------------------
// The created Pi4J Context initializes platforms, providers
// and the I/O registry. To help you to better understand this
// approach, we print out the info of these. This can be removed
// from your own application.
// OPTIONAL
PrintInfo.printLoadedPlatforms(console, pi4j);
PrintInfo.printDefaultPlatform(console, pi4j);
PrintInfo.printProviders(console, pi4j);
// Here we will create I/O interfaces for a (GPIO) digital output
// and input pin. We define the 'provider' to use PiGpio to control
// the GPIO.
var ledConfig = DigitalOutput.newConfigBuilder(pi4j)
.id("led")
.name("LED Flasher")
.address(PIN_LED)
.shutdown(DigitalState.LOW)
.initial(DigitalState.LOW)
.provider("pigpio-digital-output");
var led = pi4j.create(ledConfig);
var buttonConfig = DigitalInput.newConfigBuilder(pi4j)
.id("button")
.name("Press button")
.address(PIN_BUTTON)
.pull(PullResistance.PULL_DOWN)
.debounce(3000L)
.provider("pigpio-digital-input");
var button = pi4j.create(buttonConfig);
button.addListener(e -> {
if (e.state() == DigitalState.LOW) {
pressCount++;
console.println("Button was pressed for the " + pressCount + "th time");
}
});
// OPTIONAL: print the registry
PrintInfo.printRegistry(console, pi4j);
while (pressCount < 5) {
if (led.equals(DigitalState.HIGH)) {
console.println("LED low");
led.low();
} else {
console.println("LED high");
led.high();
}
Thread.sleep(500 / (pressCount + 1));
}
// ------------------------------------------------------------
// Terminate the Pi4J library
// ------------------------------------------------------------
// We we are all done and want to exit our application, we must
// call the 'shutdown()' function on the Pi4J static helper class.
// This will ensure that all I/O instances are properly shutdown,
// released by the the system and shutdown in the appropriate
// manner. Terminate will also ensure that any background
// threads/processes are cleanly shutdown and any used memory
// is returned to the system.
// Shutdown Pi4J
pi4j.shutdown();
}
}
