2 replies to this topic

[spcboog]

Hi all, I am trying to read the WHO_AM_I register from my ITG-3200 (Sparkfun breakout board: http://www.sparkfun.com/products/9801). I couldn't get this to work with 4.1.0.6 so I performed the required upgrade steps to get to 4.2: - Netduino Plus - .NET MF SDK 4.2 RTM - Netduino SDK 4.2.0 June 11 Beta - Updated tinybooterloader and firmware (4.2 RC3) Now I'm trying with the following code: var gyroscope = new I2CDevice(new I2CDevice.Configuration(0x69, 400)); var readBuffer = new byte[1]; var actions = new I2CDevice.I2CTransaction[] { I2CDevice.CreateWriteTransaction(new byte[] { 0x00 }), CreateReadTransaction(readBuffer, 0x00, 1) }; var result = gyroscope.Execute(actions, 1000); Where CreateReadTransaction is the method posted here: http://forums.netdui...rt-bit-support/ 0x00 is the WHO_AM_I register address. Previously (with 4.1.0.6), gyroscope.Execute(actions, 1000) would return 1, I'm assuming that the read action failed since the buffer remained zeroed. With the new firmware, gyroscope.Execute(actions, 1000) returns 0 (implying that neither action is successful?). Does anyone have any ideas? thanks The ITG-3200 datasheet is here: http://invensense.co...200-00-01.4.pdf

[spcboog]

Sorry folks, I didn't have pullups, added 2 4k7's and the read works now. I had mistakenly thought that the sparkfun breakout board already had pullups included but there are just spots for you to add them yourself. I got a BlinkM to see if I could get anything I2C to work at all and when I couldn't get that to work either (also due to me thinking the pullups were already included), I read this: http://forums.netdui...__fromsearch__1 which pointed to the missing pullups.

[Jack Chidley]

I got this to work too, thanks to this forum entry and a host of other, unremembered, entries. I used 10k pull up resistors.

My horrible but work-in-progress, code.

using System;
using System.Reflection;
using System.Net;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.NetduinoPlus;

namespace NPlus_IT3200
{
    public class Program
    {
        //create a empty i2c device object
        static I2CDevice myI2C = new I2CDevice(new I2CDevice.Configuration(0, 0));

        public static void Main()
        {
            int r;

            while (true)
            {
                r = (int)read_gyro_state(); //read value from gyro
                Debug.Print("R = " + r.ToString());
                Thread.Sleep(1000);
            }
        }


        I2CDevice.I2CWriteTransaction CreateWriteTransaction(byte[] buffer, uint internalAddress, byte internalAddressSize)
        {
            I2CDevice.I2CWriteTransaction writeTransaction = I2CDevice.CreateWriteTransaction(buffer);
            Type writeTransactionType = typeof(I2CDevice.I2CWriteTransaction);

            FieldInfo fieldInfo = writeTransactionType.GetField("Custom_InternalAddress", BindingFlags.NonPublic | BindingFlags.Instance);
            fieldInfo.SetValue(writeTransaction, internalAddress);

            fieldInfo = writeTransactionType.GetField("Custom_InternalAddressSize", BindingFlags.NonPublic | BindingFlags.Instance);
            fieldInfo.SetValue(writeTransaction, internalAddressSize);

            return writeTransaction;
        }

        I2CDevice.I2CReadTransaction CreateReadTransaction(byte[] buffer, uint internalAddress, byte internalAddressSize)
        {
            I2CDevice.I2CReadTransaction readTransaction = I2CDevice.CreateReadTransaction(buffer);
            Type readTransactionType = typeof(I2CDevice.I2CReadTransaction);

            FieldInfo fieldInfo = readTransactionType.GetField("Custom_InternalAddress", BindingFlags.NonPublic | BindingFlags.Instance);
            fieldInfo.SetValue(readTransaction, internalAddress);

            fieldInfo = readTransactionType.GetField("Custom_InternalAddressSize", BindingFlags.NonPublic | BindingFlags.Instance);
            fieldInfo.SetValue(readTransaction, internalAddressSize);

            return readTransaction;
        }


        //Function to read value from ITG3200 gyro
        //16-bit value over two registers 
        public static double read_gyro_state()
        {
            byte[] WHO_AM_I = new byte [] {0x00};
            byte[] SMPLRT_DIV = new byte[] { 0x15 };
            byte[] DLPF_FS = new byte[] { 0x16 };
            byte[] GYRO_XOUT_H = new byte[] { 0x1D };
            byte[] GYRO_XOUT_L = new byte[] { 0x1E };
            byte[] GYRO_YOUT_H = new byte[] { 0x1F };
            byte[] GYRO_YOUT_L = new byte[] { 0x20 };
            byte[] GYRO_ZOUT_H = new byte[] { 0x21 };
            byte[] GYRO_ZOUT_L = new byte[] { 0x22 };
            byte[] readBuffer = new byte[1];
            int val = 0;
            double readX = 0, readY = 0, readZ = 0;

            myI2C.Config = new I2CDevice.Configuration(0x69, 400); //Set i2c device configuration

            readX = ReadGyroAxis(GYRO_XOUT_H, GYRO_XOUT_L, readBuffer, val);
            readY = ReadGyroAxis(GYRO_YOUT_H, GYRO_YOUT_L, readBuffer, val);
            readZ = ReadGyroAxis(GYRO_ZOUT_H, GYRO_ZOUT_L, readBuffer, val);

            return readX;
        }

        private static int ReadGyroAxis(byte[] GYRO_XOUT_H, byte[] GYRO_XOUT_L, byte[] readBuffer, int val)
        {
            myI2C.Execute(new I2CDevice.I2CTransaction[] {
                    I2CDevice.CreateWriteTransaction(GYRO_XOUT_H)
                    ,
                I2CDevice.CreateReadTransaction(readBuffer)
                }, 5000);

            val = (sbyte)readBuffer[0] << 8; //bit shift first resiter value

            myI2C.Execute(new I2CDevice.I2CTransaction[] {
                    I2CDevice.CreateWriteTransaction(GYRO_XOUT_L)
                    ,
                I2CDevice.CreateReadTransaction(readBuffer)
                }, 5000);

            val = val | readBuffer[0]; //combined with second register value

            return (int) (val / 14.735); //apply scaling and return
        }
    }

}

Jack