Communication between Java, Dynamixel AX-12A and Raspberry Pi

[Paulo Consoni]

Good Evening

We're working with PI4J and we are tring to transcribe this python code to Java:

   from time import sleep

   from serial import Serial

   import RPi.GPIO as GPIO

    class Ax12:

       # important AX-12 constants

       AX_START = 255

       AX_GOAL_LENGTH = 5

       AX_WRITE_DATA = 3

       AX_GOAL_POSITION_L = 30

       TX_DELAY_TIME = 0.00002

        # RPi constants

       RPI_DIRECTION_PIN = 2

       RPI_DIRECTION_TX = GPIO.HIGH

       RPI_DIRECTION_RX = GPIO.LOW

       RPI_DIRECTION_SWITCH_DELAY = 0.0001

        # static variables

       port = None

       gpioSet = False

        def __init__(self):

           if(Ax12.port == None):

               Ax12.port = Serial("/dev/ttyAMA0", baudrate=1000000, timeout=0.001)

           if(not Ax12.gpioSet):

               GPIO.setwarnings(False)

               GPIO.setmode(GPIO.BCM)

               GPIO.setup(Ax12.RPI_DIRECTION_PIN, GPIO.OUT)

               Ax12.gpioSet = True

           self.direction(Ax12.RPI_DIRECTION_RX)

        def direction(self,d):

           GPIO.output(Ax12.RPI_DIRECTION_PIN, d)

           sleep(Ax12.RPI_DIRECTION_SWITCH_DELAY)

        def move(self, id, position):

           self.direction(Ax12.RPI_DIRECTION_TX)

           Ax12.port.flushInput()

           p = [position&0xff, position>>8]

           checksum = (~(id + Ax12.AX_GOAL_LENGTH + Ax12.AX_WRITE_DATA + Ax12.AX_GOAL_POSITION_L + p[0] + p[1]))&0xff

           outData = chr(Ax12.AX_START)

           outData += chr(Ax12.AX_START)

           outData += chr(id)

           outData += chr(Ax12.AX_GOAL_LENGTH)

           outData += chr(Ax12.AX_WRITE_DATA)

           outData += chr(Ax12.AX_GOAL_POSITION_L)

           outData += chr(p[0])

           outData += chr(p[1])

           outData += chr(checksum)

           print(Ax12.AX_START,Ax12.AX_START,id,Ax12.AX_GOAL_LENGTH,Ax12.AX_WRITE_DATA,Ax12.AX_GOAL_POSITION_L,p[0],p[1],checksum)

           print(chr(Ax12.AX_START),chr(Ax12.AX_START),chr(id),chr(Ax12.AX_GOAL_LENGTH),chr(Ax12.AX_WRITE_DATA),chr(Ax12.AX_GOAL_POSITION_L),chr(p[0]),chr(p[1]),chr(checksum))

           Ax12.port.write(outData)

           sleep(Ax12.TX_DELAY_TIME)

  

This code run the AX-12A motor in the wished position, and we are tring to do the same using Java (IDE: BlueJ). We have translated the most part of the code, and we just need a help to correct it.

    import com.pi4j.io.gpio.GpioController;

   import com.pi4j.io.gpio.GpioFactory;

   import com.pi4j.io.gpio.GpioPinDigitalOutput;

   import com.pi4j.io.gpio.PinState;

   import com.pi4j.io.gpio.RaspiPin;

   import com.pi4j.wiringpi.Serial;

    public class Ax12 {

   

       # important AX-12 constants

       public static final int AX_START = 255;

       public static final int AX_GOAL_LENGTH = 5;

       public static final int AX_WRITE_DATA = 3;

       public static final int AX_GOAL_POSITION_L = 30;

       public static final long TX_DELAY_TIME = 2; #0.00002

        # RPi constants

       public static final int RPI_DIRECTION_PIN = 2;

   

       # Opening GPIO comunication and defining TX and RX ports

        final static GpioController raspi = GpioFactory.getInstance();

        final static GpioPinDigitalOutput RPI_DIRECTION_TX = raspi.provisionDigitalOutputPin(RaspiPin.GPIO_14, "TX", PinState.HIGH);

       final static GpioPinDigitalOutput RPI_DIRECTION_RX = raspi.provisionDigitalOutputPin(RaspiPin.GPIO_15, "RX", PinState.LOW);

   

       public static final long RPI_DIRECTION_SWITCH_DELAY = 1; # 0.0001

        # static variables

       static int port = 0;  # static Integer port = null;

       static boolean gpioSet = false;

        Ax12(){

            if(Ax12.port==0)

                       Ax12.port = Serial.serialOpen(Serial.DEFAULT_COM_PORT, 1000000);

           

           if (!Ax12.gpioSet)

                     Ax12.gpioSet = true;

       }

   

   

       public static void direction(int d) throws InterruptedException {

       

           if (d==1)

               raspi.provisionDigitalOutputPin(RaspiPin.GPIO_02, "2-H", PinState.HIGH);

           else

               raspi.provisionDigitalOutputPin(RaspiPin.GPIO_02, "2-L", PinState.LOW);

   

           Thread.sleep(RPI_DIRECTION_SWITCH_DELAY);

       }

   

   

       public void move (int id, int position) throws InterruptedException {

       

           Ax12.direction(1); # TX port on

       

           Serial.serialFlush(Ax12.port);

           System.out.println("it move!");

            int [] p = new int[2];

       

           p[0] = position&0xff;

           p[1] = position >> 8;

       

            int checksum = (~(id + Ax12.AX_GOAL_LENGTH + Ax12.AX_WRITE_DATA + Ax12.AX_GOAL_POSITION_L + p[0] + p[1]))&0xff;

       

           String outData;

           outData = "\\x"+Integer.toHexString(Ax12.AX_START);

            outData += "\\x"+Integer.toHexString(Ax12.AX_START);

           outData += "\\x0"+Integer.toHexString(id);

           outData += "\\x0"+Integer.toHexString(Ax12.AX_GOAL_LENGTH);

           outData += "\\x0"+Integer.toHexString(Ax12.AX_WRITE_DATA);

           outData += "\\x"+Integer.toHexString(Ax12.AX_GOAL_POSITION_L);

           outData += "\\x0"+Integer.toHexString(p[0]);

           outData += "\\x0"+Integer.toHexString(p[1]);

           outData += "\\x"+Integer.toHexString(checksum);

           System.out.println(outData);

           Serial.serialPuts(Ax12.port, outData);

           Thread.sleep(Ax12.TX_DELAY_TIME);

       

       }

    }

The code compiled, but didn't move the motor. We need to understand where are our mistake. We believe it is in the GPIO library used, but we have a uncertainty about that. If someone could help us, we thank you.