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Problem getting I2C to start

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#1 Pablo020


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Posted 06 December 2014 - 01:34 AM

Hello folks,

I have a ND+2, VS2103, Latest firmware etc..


I run the following code snippet:

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;

namespace BasicMaster
    public class Program
        private static I2CDevice.Configuration _i2cDeviceConfiguration = null;
        private static I2CDevice _i2cDevice;
        public static void Main()
            Debug.Print("Main started");
            _i2cDeviceConfiguration = new I2CDevice.Configuration(0x00, 400);
            _i2cDevice = new I2CDevice(_i2cDeviceConfiguration);

            for (int i = 0; i < 100000; i++)
        private static void SendOnlyI2cMessage(Int32 counter)
            I2CDevice.I2CTransaction[] transactions = new I2CDevice.I2CTransaction[1];

            byte[] RegisterNum = new byte[1] { 2 };
            transactions[0] = I2CDevice.CreateWriteTransaction(RegisterNum);
            Int32 executeResult = _i2cDevice.Execute(transactions, 1000);
            if (executeResult == 0)
                Debug.Print("I2C transaction, Counter = " + counter.ToString() + ", ExecuteResult = Failed (value = 0)");
                Debug.Print("I2C transaction, Counter = " + counter.ToString() + ", ExecuteResult = " + executeResult.ToString());

I connected the SD and SC pins via 10K resistors to the +3.3V.

A scope is connected to both the clock and the data (SC and SD pins).



Scenario 1:

- build app

- deploy and debug app

- app starts and code is running, as I see the debug print stuff coming in.



I see both channels on the scope indicating a flat 3.3V... but no signs of any signal generated by the netduino. (See first attachment)

Strange ... I expected the execute to fail, however, I ought to see some 'proof' of attempts on the signals.


Then ... 

- I disconnect 3.3V pin, and reconnect ....


I see the expected signal. See second attachment.



The same effect I get in the following scenario:


Scenario 2:

- above code is running. I did the 3.3V disconnect - reconnect routine. And i can see the signal.

- I press the reset button of the ND+2

- After restart, again I see the image 1... a flat 3.3V

- Disconnect 3.3V and Reconnect 3.3V 

- Result: image 2, a clear signal!



Am I doing something wrong?

Can I fix this from the software?


Any feedback would be appreciated!!



Attached Files

#2 dino4net


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Posted 08 December 2014 - 04:02 PM

There was a workaround some time ago I still use in my I2C projects.

Put it at the beginning of the project to give the port the right level. Also advice to get a Scanna Plus device from to debug this type of problems in minutes.

            //Workaround for a bug where you need to disconnect the I2C bevore it works.
            OutputPort p = new OutputPort(Pins.GPIO_PIN_SDA, true);

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