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DRV8353R: SPI registers Read & write issues

user4884131
Prodigy 90 points
Part Number: DRV8353R

Hi,

We are using the DRV8353RS evaluation board connected on a motor for motorization purpose. When the motor is not activated, we are able to access SPI registers without any read/write issues.

Each time we change the SPI register value, we immediatly do a read back to validate what we just sent. All registers are lock once properly write on bootup and only bit 0, 1 & 2 of register 2 are accessible.

We have some write and read back issue when the registers are address at the same time that the motor run. We looked at the SPI signals and they are all clean.

Here below is a screenshot where we write 0xC0 in register 2 and get 0x180 as readback. Seem to have some kind of shifted bit or so.

Here below is another example when we write 0xC0 in register 2 and get 0x00 as readback.

The goal here is simply to change the coast bit depending of the operating phase of the motor control.

Can you please help us on that?

Best Regards,

Pierre-Luc

  • 0
    TI__Guru 65490 points

    Pierre,

    Could you detail for me the value of the registers before the write, the value you are writing, and then the readback?

    I want to see if any bits are changing or if there are some bits that are staying the same.

    Where are you measuring the SPI? Is the board or code modified at all?

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 90 points

    Hi Adam,

    We are only changing register 2 values during system operation as said earlier.

    Register 2 values is 0xC0 or 0xC4 pepending if we want the system to be operated in coast mode or not. The readback value can be anything, but in the two examples I sent you on the first post was 0x180 and 0x00.

    The SPI signals are measured on our control board (using a ST microcontroller) directly on the connector where wire are connected to the DRV8353RS evaluation board.

    We added a 5V LDO from the embedded 12V buck to supply motor hall sensors. Driver IC VM is supplied from the 12V embedded buck.

    Thanks,

    Pierre-Luc

  • 0 in reply to user4884131
    TI__Guru 65490 points

    Pierre-Luc,

    Did you check if the GNDing between the boards is correct? Was this issue resolved?

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 90 points

    Hi Adam,

    The grounding between seems OK, we have a good system ground connection.

    Anything else we should look at?

    Thanks,

    Pierre-Luc

  • 0 in reply to user4884131
    TI__Guru 65490 points

    Pierre-Luc,

    Unfortunately I'm not sure why you are seeing this issue. Have you tried a second board?

    The only thing I can think of is that the motor spinning is causing the GND to bounce or similar which is causing the read/write to have an issue.

    Maybe the SPI readback on the ST board is not functioning correctly when the motor is spinning?

    Can you check if the SPI works as expected with the original MCU board from TI?

    Regards,

    -Adam