[charrisTTI]

I spent the better part of a day looking at the magnetic encoder I/O options. We ruled out the analog angle output because of the slow response at the rollover point. I did not give the PWM output much thought. I tried two different approaches for which I am including code samples. The first reads the data digitally using the SPI support and the second uses two analog channels to read the sin/cos outputs (be sure to remove the solder jumper to enable these ports).

Here is the digital one using SPI:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package edu.wpi.first.wpilibj;

import edu.wpi.first.wpilibj.fpga.tSPI;

/**
 *
 * @author charris
 */
public class AS5030FourWireSPI extends SensorBase {

    public class AS5030Result
    {
        public double angle;
        public int agc;
    }


    tSPI spi;
    DigitalModule module;
    int slot;
    int clockPin;
    int dataOutPin;
    int dataInPin;
    int chipSelectPin;


    public AS5030FourWireSPI( int slotParam, int clockPinParam, int dataOutPinParam, int dataInPinParam, int chipSelectPinParam )
    {
        slot = slotParam;
        clockPin = clockPinParam;
        dataOutPin = dataOutPinParam;
        dataInPin = dataInPinParam;
        chipSelectPin = chipSelectPinParam;
        
        // get our module
        module = DigitalModule.getInstance(slot);

        // create SPI instance
        //spi = new tSPI();

        // allocate our pins
        module.allocateDIO(clockPin, false);
        module.allocateDIO(dataOutPin, false);
        module.allocateDIO(dataInPin, true);
        module.allocateDIO(chipSelectPin, false);

        // setup for SPI
        tSPI.writeChannels_SCLK_Module(DigitalModule.slotToIndex(slot));
        tSPI.writeChannels_SCLK_Channel(DigitalModule.remapDigitalChannel(clockPin-1));

        tSPI.writeChannels_MOSI_Module(DigitalModule.slotToIndex(slot));
        tSPI.writeChannels_MOSI_Channel(DigitalModule.remapDigitalChannel(dataOutPin-1));

        tSPI.writeChannels_MISO_Module(DigitalModule.slotToIndex(slot));
        tSPI.writeChannels_MISO_Channel(DigitalModule.remapDigitalChannel(dataInPin-1));
    }

    public void initialize()
    {
        // set chip select low to start
        module.setDIO(chipSelectPin, true);

        // data is valid on rising edge of clock
        tSPI.writeConfig_DataOnFalling(false);

        // set the bit order
        tSPI.writeConfig_MSBfirst(true);

        tSPI.strobeReset();
        tSPI.strobeClearReceivedData();
    }

    public AS5030Result getData( )
    {
        // select the chip
        module.setDIO(chipSelectPin, false);

        // write the 5 bit command
        // set the width
        tSPI.writeConfig_BusBitWidth(5);

        // write the data to load
        tSPI.writeDataToLoad(0x1F);

        // strobe out the data
        tSPI.strobeLoad();

        // wait for completion
        while( !tSPI.readStatus_Idle() )
        {
            java.lang.Thread.yield();
        }

        // change back to 16 bits
        tSPI.writeConfig_BusBitWidth(16);
        // clear the data to load
        tSPI.writeDataToLoad(0x0);

        // clear received data
        tSPI.strobeClearReceivedData();

        // strobe in the data
        tSPI.strobeLoad();


        // wait for completion
        //while( !tSPI.readStatus_Idle() )
        while( tSPI.readReceivedElements() == 0 )
        {
            java.lang.Thread.yield();
        }

        // strobe in the received data
        tSPI.strobeReadReceivedData();

        // read the data
        long rawData = tSPI.readReceivedData();

        // deselect the chip
        module.setDIO(chipSelectPin, true);

        AS5030Result result = new AS5030Result();

        long rawAngle = rawData & 0xFF;

        int agc = (int)((rawData >> 8) & 0x3F);

        result.angle = (double)rawAngle * 360.0 / 256.0;
        result.agc = agc;
        
        return result;
    }
}

Here is the dual analog input approach:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package edu.wpi.first.wpilibj;

import  com.sun.squawk.util.MathUtils;

/**
 *
 * @author charris
 */
public class AS5030DualAnalog extends SensorBase implements PIDSource {

    private static final double biasVoltage = 2.25;
    private AnalogChannel sinChannel;
    private AnalogChannel cosChannel;

    public AS5030DualAnalog( int slotParam, int sinChannelParam, int cosChannelParam)
    {
        sinChannel = new AnalogChannel( slotParam, sinChannelParam );
        cosChannel = new AnalogChannel( slotParam, cosChannelParam );
    }

    protected double getCos()
    {
        return cosChannel.getVoltage() - biasVoltage;
    }

    protected double getSin()
    {
        return sinChannel.getVoltage() - biasVoltage;
    }

    public double getAngle()
    {
        // calculate the angle
        double theta = MathUtils.atan2( getSin(), getCos() );
        // convert to degrees
        return Math.toDegrees(theta) + 180.0;
    }

    /**
     * Get the angle of the encoder for use with PIDControllers
     * @return the current angle according to the encoder
     */
    public double pidGet() {
        return getAngle();
    }


}

Give them a try.