TheIceManProgrammeth

Thanks Paul. Got readings from both the magnet and accelerometer now but I'm intrigued as to why the standard I2C stuff didn't work. Think one of the other posters mentioned repeated-start condition so going to experiment with that to see if I can see what is wrong with the standard transaction based stuff.

Will post all results to the wiki once I've finished.

Seems so easy now it's working properly!

I had the same issue. Try amending:

byte write = { AddressOfFirstRegisterIneed };

to

byte write = { AddressOfFirstRegisterIneed | (1 << 7) };

Ok update on this one. I eventually started to get some readings when I switched the I2C sensor code to the toolbox MultiI2c but only for the magnet not the accelerometer. No resistors needed and worked using the sensor shield I bought so haven't wasted money after all.

Will post the code when I get the accelerometer working!

Thanks to Paul for his suggestions and I've certainly learnt a lot more about how I2C works!

Haha thanks Paul well this is the sensor for the heading so it could end up anywhere in Berkshire if it doesn't work! ;-)
 
So the code sends 8bytes to be populated by the sensor and then checks if the number of bytes coming back is equal to the buffer.

            lock (_slaveDevice)

            {

                // the i2c data is received here from the device.

                int transferred = _slaveDevice.Execute(readXAction, transactionTimeout);

                // make sure the data was received.

                if (transferred != readBuffer.Length)

                   throw new Exception("Could not read from device.");

            }

When I use the code above transferred is always 0. When I use the same _slaveDevice.Execute method for the write it returns 2 for the init and 1 for the pre-read send. Adding the resistors has no impact (I've placed one between the power and the SDA and one one betwen the SCL and power). Even without anything connected to the netduino the write returns 2 and 1 from the method and the read still returns 0.

So what I can't get my head round is why is the netduino saying the write worked when clearly there was nothing attached to it? Your earlier post suggested the ACK was being wrongly interpreted but since there is nothing connected to the pin where did the ACK come from?

Thanks for any suggestions you can give me.

Cool hopefully you will see one of my netduino projects flying around the Reading area soon!

So I tried the i2C again and still nothing.

With absolutely nothing attached to the netduino the write seems to work sending 2 bytes for the init and 1 for the pre-read. The read returns 0. This is exactly the same result when I plug in the sensor with or without resistors between them and the board.

I did notice the arduino library code for the sensor was slightly different to the Netduino conversion but even changing those had no effect and would explain why the sensor seems to have no impact on the results whatsoever.

Pretty frustrating. Is there any way to test the i2c using something simpler?

Thanks again in advance for any help. I'm sure it's probably something silly.