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BQ79631-Q1: Problems after enable TSREF (Evaluation Module BQ79631EVM)

Christoph Lackinger
Prodigy 60 points
Part Number: BQ79631-Q1

Dear Ladies and Gentlemen!

I am working with an evaluation module (BQ79631EM-039) and communicate with a microcontroller (STM32H745) via UART. I configure the Main ADC register (ADC_CTRL1, ADC_CTRL2, ADC_CONF1 and ADC_CONF2) and the GPIO register (GPIO_CONF1, GPIO_CONF2, GPIO_CONF3 and GPIO_CONF4) and after I enabled TSREF (CONTROL2) and waited 380us (as it is written in the manual) I can't communicate with the evaluation module anymore. Am I making a mistake here? Can someone help me with this problem.

BR, Christoph

  • 0
    TI__Intellectual 1845 points

    Good Evening Christoph,

    I just want to ensure you properly woke up the device and went through the auto address sequence is that correct? Can you double check that the CRC for your commands are correct. When you say you cannot communicate what do you mean exactly? Does the device go into shutdown or does something else happen?

    Thanks,

    Chase

  • 0 in reply to Chase Fagen
    Prodigy 60 points

    Hi Chase!

    The evaluation  module is supplied with 5V (5V_LV). First I wake up the module with a wake-up ping. The green LED starts to light up and the current consumption increases to approx. 180mA. The auto-addressing sequence starts after 10ms (enable auto addressing mode -> set address to 0x00 -> config register COMM_CTRL). After that TSREF is enabled (CONTROL2). 380us is waited here. Then the GPIO register (GPIO_CONF1, GPIO_CONF2, GPIO_CONF3 and GPIO_CONF4) and the main ADC register (ADC_CTRL1, ADC_CTRL2, ADC_CONF1 and ADC_CONF2) are configured. At the end I wait approx. 1.6ms and read out the ADC_STAT1 register (broadcast read). Now the module no longer responds (no UART message) and the GPIOs are not set correctly (they are all at 0V). The CRC calculation is correct. If I wait 6.5ms after TSREF has been enabled and wait 100us between each configuration (GPIO_CONFIG1, GPIO_CONFIG2, ...) everything works. The module responds to all my requests. Do I have to wait between the configurations? I have not found anything about this in the manual.

    BR, Christoph

  • 0 in reply to Christoph Lackinger
    TI__Intellectual 1845 points

    Hi Christoph,

    I have an intuition that you are not receiving data because the ADC has not finished converting. Are you enabling the LPF? If you are, you need to wait sufficient time for the LPF to settle to properly retrieve ADC data.

    Thanks,

    Chase

  • 0 in reply to Chase Fagen
    Prodigy 60 points

    Hi Chase!

    The digital low pass filter (LPF) is disabled. It is not only that the module no longer responds, but also that the GPIOs are not set correctly. GPIO2 should be an output and high.

    Christoph

  • 0 in reply to Christoph Lackinger
    TI__Intellectual 1845 points

    Christoph,

    What is your UART baud rate? This could possibly be the source of your timing issues.

    Chase