Pi4J Version 2

The pigpio library is loaded through a call to

libraries/pi4j-library-pigpio/src/main/java/com/pi4j/library/pigpio/util/NativeLibraryLoader.java/load(String fileName, String libName)

This call comes from libraries/pi4j-library-pigpio/src/main/java/com/pi4j/library/pigpio/internal/PIGPIO.java where there's a static block defined calling the NativeLibraryLoader.load() method:

static {

        // Load the platform library

        NativeLibraryLoader.load("libpi4j-pigpio.so", "pi4j-pigpio");

    }

In the load() method a check is done if the library cannot be found through the System properties.  But that returns null on a RPi.  Hence, the OS architecture is then requested and on a RPi this should be arm (unless you have the 64-bit OS in use, which should give arm64, I guess...).

Using NetBeans, create a new project.  Call it I2cTest (what's in a name...).  We're going to manipulate an MCP23016 IO expander very basically.

Next, once the project is created, include the necessary libraries: right-click on the Libraries node in the project and select Add Library...

Now add the following code into the I2cTest application:

import com.pi4j.Pi4J;

import com.pi4j.context.Context;

import com.pi4j.io.i2c.I2C;

import com.pi4j.io.i2c.I2CConfig;

import com.pi4j.io.i2c.I2CProvider;

import com.pi4j.util.Console;

public class I2cTest {

    private static final int I2C_BUS = 15;

    private static final int MCP23017_ADDRESS = 0x22;

    private static final byte MCP23017_IODIR_A = 0x00;

    private static final byte MCP23017_OLAT_A = 0x14;

    private static final byte TCA9534_REG_ADDR_CFG = 0x03;

        /**

     * @param args the command line arguments

     */

    public static void main(String[] args) {

        // TODO code application logic here

        I2cTest i2cTest = new I2cTest();

        i2cTest.doStart();

    }

    private void doStart() {

        Console console = new Console();

        console.box("Welcome");

        Context pi4j = Pi4J.newAutoContext();

        I2CProvider i2CProvider = pi4j.provider("pigpio-i2c");

        I2CConfig i2cConfig = I2C.newConfigBuilder(pi4j).id("MCP23017").bus(I2C_BUS).device(MCP23017_ADDRESS).build();

        try (I2C mcp23017 = i2CProvider.create(i2cConfig)) {

            int config = mcp23017.readRegister(MCP23017_IODIR_A);

            if (config < 0) {

                    throw new IllegalStateException(

                                        "Failed to read configuration from address 0x" + String.format("%02x", MCP23017_IODIR_A));

            }

            byte currentState = (byte) mcp23017.readRegister(MCP23017_IODIR_A);

            if (config != 0x00) {

                System.out.println("MCP23017 is not configured as OUTPUT, setting register 0x" + String

                                        .format("%02x", MCP23017_IODIR_A) + " to 0x00");

                currentState = 0x00;

                mcp23017.writeRegister(MCP23017_IODIR_A, currentState);

                mcp23017.writeRegister(MCP23017_IODIR_A, (byte) 0x00);

            }

            // bit 8, is pin 1 on the board itself, so set pins in reverse:

            currentState = setPin(currentState, 8, mcp23017, true);

            sleep(500);

            currentState = setPin(currentState, 8, mcp23017, false);

            sleep(500);

            currentState = setPin(currentState, 7, mcp23017, true);

            sleep(500);

            currentState = setPin(currentState, 7, mcp23017, false);

            sleep(500);

        }

    }

    private void sleep(long time) {

        try {

            Thread.sleep(time);            

        }

        catch (InterruptedException iex) {

            System.out.println("Exception: [" + iex.getMessage() + "].");

        }

    }

    private byte setPin(byte currentState, int pin, I2C mcp23017, boolean high) {

        byte newState;

        if (high) {

            newState = (byte) (currentState | (1 << pin));

        }

        else {

            newState = (byte) (currentState & ~(1 << pin));

        }

        System.out.println("Setting MCP23017 to new state " + asBinary(newState));

        mcp23017.writeRegister(MCP23017_OLAT_A, newState);

        return newState;

    }

    private String asBinary(byte b) {

        StringBuilder sb = new StringBuilder();

        sb.append("b");

        sb.append(((b >>> 7) & 1));

        sb.append(((b >>> 6) & 1));

        sb.append(((b >>> 5) & 1));

        sb.append(((b >>> 4) & 1));

        sb.append("_");

        sb.append(((b >>> 3) & 1));

        sb.append(((b >>> 2) & 1));

        sb.append(((b >>> 1) & 1));

        sb.append(((b >>> 0) & 1));

        return sb.toString();

    }

}