TMS320F28335: F28335

Anu B

Part Number: TMS320F28335

Hello,

The module 12 of the following resource is for I2C communication.

www.ti.com/.../ssqc019

The example codes for I2C communication just poll ARDY and never check if the receiver had actually acknowledged it, Why is that so?

This is what is done:

I2caRegs.I2CCNT = 1; // 1 byte message
I2caRegs.I2CDXR = POINTER_TEMPERATURE;
I2caRegs.I2CMDR.all = 0x6620; // master-receiver, START, STOP
while(I2caRegs.I2CSTR.bit.ARDY == 0); // poll ARDY- wait for STOP condition

After this, the next transmission starts.

So, without checking (or polling) for ACK bit, the next transmission is started. Why is that?

Everywhere, it has been told that if the slave device does not acknowledge the transfer, then the next data/ transfer can not be initiated. But the example code doesn't do that. So, isn't that supposed to be wrong since we will never know if the receiver had actually received it?

over 3 years ago

0 Kevin Allen18 over 3 years ago

TI__Mastermind 38275 points

Hi Anu,

I'll review the code some tomorrow. If a NACK is not detected, either by interrupt or polling the NACK status bit, after the data is transmitted out (i.e. ARDY set to 1, see bit description in TRM) then you know that the byte was received OK.

Best,

Kevin

0 Anu B over 3 years ago in reply to Kevin Allen18

Intellectual 335 points

But the example code never polls NACK. Only the ARDY is polled.

0 Kevin Allen18 over 3 years ago in reply to Anu B

TI__Mastermind 38275 points

Hi Anu,

Yes, that's right. The example code does not have NACK checking inplemented.

You could add this after the ARDY check if you'd like to verify that a NACK was not received. Something similar to the below:

    #if NACK_CHECK // check if NACK was received
        if(I2caRegs.I2CSTR.bit.NACK == 1)
        {
            I2caRegs.I2CMDR.bit.STP = 1;
            I2caRegs.I2CSTR.all = I2C_CLR_NACK_BIT;

            Status = I2C_ERROR;
            return Status;
        }
    #endif

Best,

Kevin

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TMS320F28335: F28335