MicroMag 3-axis Magnetometer

Hi, this is my first "real" project using the Netduino. I don't have a lot of experience in hardware programming and the code below is a simple port of what I already found online. But the code combined with the datasheet taught me a few things. I just hope what I learned is consistent with other hardware and datasheet.

I tested the results against a friend's phone that has a built-in compass and they agreed.

http://www.sparkfun....products_id=244

I don't have a diagram to show you but hopefully the pin assignments will help.

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;

namespace Magnetometer
{
    public class Program
    {

        static Cpu.Pin SCLK = Pins.GPIO_PIN_D7;
        static Cpu.Pin MISO = Pins.GPIO_PIN_D6;
        static Cpu.Pin MOSI = Pins.GPIO_PIN_D5;
        static Cpu.Pin SSNOT = Pins.GPIO_PIN_D4;
        static Cpu.Pin DRDY = Pins.GPIO_PIN_D3;
        static Cpu.Pin RESET = Pins.GPIO_PIN_D2;
        static OutputPort sclk = new OutputPort(SCLK, false);
        static OutputPort reset = new OutputPort(RESET, false);
        static OutputPort mosi = new OutputPort(MOSI, false);
        static OutputPort ssnot = new OutputPort(SSNOT, false);
        static InputPort miso = new InputPort(MISO, false, Port.ResistorMode.Disabled);
        static InputPort drdy = new InputPort(DRDY, false, Port.ResistorMode.Disabled);
        static float x = 0, y = 0, z = 0;
        static float heading = 0;

        public static void Main()
        {
            // write your code here
            while (true)
            {
                x = QueryMag(0);
                y = QueryMag(1);
                z = QueryMag(2);
                heading = getHeading(x, y, z);
                Debug.Print("X: " + x.ToString());
                Debug.Print("Y: " + y.ToString());
                Debug.Print("Z: " + z.ToString());
                Debug.Print("Heading: " + heading.ToString());
                Thread.Sleep(5000);

            }
        }

        private static float getHeading(float x, float y, float z)
        {
            heading = 0;
            if ((x == 0) && (y < 0))
                heading = (float)(System.Math.PI / 2.0);
            if ((x == 0) && (y > 0))
                heading = (float)(3.0 * System.Math.PI / 2.0);
            if (x < 0)
                heading = (float)(System.Math.PI - MathLib.Atan(y / x));
            if ((x > 0) && (y < 0))
                heading = (float)MathLib.Atan(y / x) * -1;
            if ((x > 0) && (y > 0))
                heading = (float)(2.0 * System.Math.PI - MathLib.Atan(y / x));
            return (float)(heading * 180 / System.Math.PI);

        }

        private static void ResetMag()
        {
            reset.Write(false);
            Thread.Sleep(2);
            reset.Write(true);
            Thread.Sleep(2);
            reset.Write(false);
            Thread.Sleep(2);
            Debug.Print("resetted");
        }

        private static void sendBit(bool hilo)
        {
            mosi.Write(hilo);
            Thread.Sleep(2);
            sclk.Write(true);
            Thread.Sleep(2);
            sclk.Write(false);
            Thread.Sleep(2);
        }

        private static float QueryMag(int axis)
        {
            ResetMag();

            sendBit(false);
            sendBit(true);
            sendBit(true);
            sendBit(false);
            sendBit(false);
            sendBit(false);

            switch (axis)
            {
                case 0 :
                    sendBit(false);
                    sendBit(true);
                    break;
                case 1 :
                    sendBit(true);
                    sendBit(false);
                    break;
                case 2 :
                    sendBit(true);
                    sendBit(true);
                    break;
                default:
                    break;
            }

            while (drdy.Read() == false)
            {
                Debug.Print("waiting for DRDY");
            }

            long total = 0;

            long sign = recieveBit();

            for (int ii = 14; ii >= 0; ii--)
            {
                long thisbit = recieveBit();
                thisbit = thisbit << ii;
                total = total | thisbit;
                Debug.Print("fired");
            }

            if (sign == 1)
            {
                total = total - 32768;
            }

            return total;
        }

        private static long recieveBit()
        {
            sclk.Write(true);
            Thread.Sleep(2);
            int bit;
            if (miso.Read() == true)
                bit = 1;
            else
                bit = 0;
            Thread.Sleep(2);
            sclk.Write(false);
            Thread.Sleep(2);
            return bit;
        }

    }
}

I needed a math library for the atan, which I got from http://www.microfram...-with-full-net/

I hope others find this useful.

Nice, Kamal! Now to think what I can build with compass logic... Chris

I tried out the code with the same part from SparkFun and it worked great for me. Thanks Kamal!