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ADS7828-Q1: I2C interface issue

Jeffrey Chung1
Expert 2460 points
Part Number: ADS7828-Q1
Other Parts Discussed in Thread: ADS7828

Hi,

I'd like to ask you I2C interface issue that slave device(ADS7828-Q1) outputs a NACK signal on the SDA line after MCU(Master) transmits Address byte(10010000). My customer wants to know the reason why. Is there any check points to resolve this issue? Please refer to the attached file below. Also, Is there any application example codes that have a sequence of initialization, start, command transmit & data receive, and data processing. Please share it with me if you have the related codes or document.

ADS7828-Q1_I2C interface.pdf

Regards, Jeffrey

  • 0
    TI__Mastermind 24940 points

    Hello,

    The SDA line is not correct, this is probably why the device is not responding. 

    In the image you provided, that SDA was changing state at the falling edge of SCLK. this is not correct. the SDA line needs to be high for this. 

    There is a good document to explain further, Understanding I2C Bus, this should help clarify the issue.

    Regards

    Cynthia

  • 0 in reply to Cynthia
    Expert 2460 points

    Hi Cynthia,

    Thanks for your support and sending an application note. I have one more question. My customer is programming the sequence code of ADS7828-Q1 through their MCU like below. Is it correct? Please let me know your recommended guide.

    U1C0_IIC_ vWriteData(U1C0TDF_MStart, 0x90);

    U1C0_IIC_ vWriteData(U1C0TDF_MTxData, 0x8C);

    U1C0_IIC_ vWriteData(U1C0TDF_MStop, 0x91);

    buffer = U1C0_IIC_ uwReadData( );

    Regards, Jeffrey

  • 0 in reply to Jeffrey Chung1
    TI__Mastermind 24940 points

    Jeffrey,

    The command they were using was correct, i was the timing and execution of the I2C that was incorrect. 

    Once they fix that, it should work properly. 

    Regards

    Cynthia

  • 0 in reply to Cynthia
    Expert 2460 points

    Hi Cynthia,

    Thanks for your support. I'll try to test what you comment, and I'll ask you additional questions if I still have a issue.

    Regards, Jeffrey