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BQ76952: Facing Issue after using another pheriferal on Same SPI bus with BQ

Raja Sharma
Prodigy 95 points
Part Number: BQ76952

Dear,

We are using BQ76952(5-volt Logic Level) and SPI flash(3.3-volt signal using voltage divider down logic level) on the same SPI bus. But getting the wrong data on Flash register read because if the BQ chip select is HIGH then also BQ holding HIGH MISO pin, that why the Flash MISO pin not providing data. If I reset the BQ (First LOW then High Reset Pin), then only able to get data from Flash but after that not get any response from BQ.

Please help with this. Is there any open drain setting in BQ that can be configured. Please suggest us how can resolve this.

  • 0
    TI__Mastermind 29270 points

    Hello Raja,

    It is not possible change the SPI behavior from the BQ device. It cannot be configured for open-drain.

    If the issue is incompatibility of the SPI, you would need to have the SPI Flash be compatible with our SPI communication. Now, I am confused by exactly what you are seeing, do you have any logic analyzer waveforms that explain what you see?

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 95 points

    Luis, 

    Thanks for the reply, we don't have a logic analyzer. Let me explain you.

    There are two devices one SPI bus with diff-diff chip select. One BQ (5 Volt logic level) and other NOR Flash(MT25QL128ABB1ESE-0AUT   3.3 Volt Logic level).

     When first both powered up, then I tried to read the Device ID of the Flash but did not get the correct value(0xfffff). Then I connected the DSO, on that, I found the MISO pin was held high from the BQ side.

    After that, I tried toggling the reset pin of BQ then I checked on DSO the MISO pin it was released from BQ then I tried to read data from Flash, getting the correct value.

    One more issue related to that. If I first power up the BQ and then start reading and writing data, communication works fine, if I toggle the RST_SHUT pin (First LOW (for 200mSec) then HIGH less) after that communication is not working with BQ.

    Please help with this

  • 0 in reply to Raja Sharma
    TI__Mastermind 29270 points

    Hello Raja,

    MISO will remain high by default, the respective devices should pull down the line when needed. Not sure why it is not able to pull it down.

    Regarding the second topic, are you following the sequence shown shown in Section 5 SPI With CRC Example of the Software Development Guide? 

    Best Regards,

    Luis Hernandez Salomon