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TIVA: Send 1 byte via I2C and receive 2 bytes

Zvi Vered
Expert 2010 points

Hello,

I'm using the following code in order to send one byte to a temp. sensor and get back 2 bytes.

But according to the I2C monitor, sometimes, only one byte is received (and not 2).

After sending 1 byte I can not send stop but a "start". This is required by the device.

Can you please check that my code is OK ?

Thanks,

Zvika

I2CMasterSlaveAddrSet(I2C6_BASE, SLAVE_ADDRESS, false);

//Send 0xAA
I2CMasterDataPut(I2C6_BASE, 0xAA);
I2CMasterControl(I2C6_BASE, I2C_MASTER_CMD_BURST_SEND_START);
while(I2CMasterBusy(I2C6_BASE)){};

I2CMasterSlaveAddrSet(I2C6_BASE, SLAVE_ADDRESS, true);

I2CMasterControl(I2C6_BASE, I2C_MASTER_CMD_BURST_RECEIVE_START);
while(I2CMasterBusy(I2C6_BASE)){};
*data=I2CMasterDataGet (I2C6_BASE);

I2CMasterControl(I2C6_BASE, I2C_MASTER_CMD_BURST_RECEIVE_FINISH);
while(I2CMasterBusy(I2C6_BASE)){};
dummy=I2CMasterDataGet (I2C6_BASE);

  • 0
    TI__Guru**** 244440 points

    Hello Zvika

    Try using the following code

    I2CMasterSlaveAddrSet(I2C6_BASE, SLAVE_ADDRESS, false);

//Send 0xAA
I2CMasterDataPut(I2C6_BASE, 0xAA);
I2CMasterControl(I2C6_BASE, I2C_MASTER_CMD_BURST_SEND_START);
while(!(I2CMasterBusy(I2C6_BASE))){};
    while(I2CMasterBusy(I2C6_BASE)){};

I2CMasterSlaveAddrSet(I2C6_BASE, SLAVE_ADDRESS, true);

I2CMasterControl(I2C6_BASE, I2C_MASTER_CMD_BURST_RECEIVE_START);
while(!(I2CMasterBusy(I2C6_BASE))){};
    while(I2CMasterBusy(I2C6_BASE)){};
*data=I2CMasterDataGet (I2C6_BASE);

I2CMasterControl(I2C6_BASE, I2C_MASTER_CMD_BURST_RECEIVE_FINISH);
while(!(I2CMasterBusy(I2C6_BASE))){};

    while(I2CMasterBusy(I2C6_BASE)){};
dummy=I2CMasterDataGet (I2C6_BASE);

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Intellectual 795 points

    Hi Amit,

    The <strong> tags are not doing what you wanted there, inside a code block.

    Zvi,

    Watch out for those <strong> tags.

  • 0 in reply to David Hubbard
    Expert 2010 points

    Hi Amit,

    Thank you for your fast reply.

    I2CMasterBusy(I2C6_BASE) returns true if the bus is busy.

    So why calling to: while ( ! I2CMasterBusy(I2C6_BASE)){}  ?

    I tried your code. It does not work.

    Can you clarify ?

    Thanks,

    Zvika

  • 0 in reply to Zvi Vered
    TI__Guru**** 244440 points

    Hello Zvi,

    After the control word is put, it takes some time for the I2C Controller to start the transaction. During this time the I2C Controller may not be busy and the original while loop may get skipped.

    By adding the new while loop, if the I2C Controller is not busy, it waits for it to get busy and then waits for it to complete. If the I2C Controller is already busy by the time the first loop is executed, it would move to the second loop.

    Since this is not working, I would have to ask you to send a scope shot or i2C Monitor details about when it is working how does the transaction look v/s when it does not work. Though this is described in the post, I would want to be clear. Also what is the slave device in this case?

    One more thing to check is if there is a clock low timeout that is occurring in the master controller?

    Regards

    Amit

  • 0 in reply to Amit Ashara
    TI__Guru**** 244440 points

    Hello Zvi,

    I am a bit confused here. If the issue is not resolved then "Verify Answer" does not qualify.

    If you can send the details as the last post and we close the issue I would be more glad.

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Expert 2010 points

    Hi Amit,

    I owe you an apology.

    I looked at your code and saw:

    while (! ....) and then while ( ) and it looks to me like a mistake.

    But after trying it, it solved the problem !!!

    Your help is highly appreciated.

    Best regards,

    Zvika