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DRV8711 SPI write and read issue

masahiko shimizu
Guru 11235 points
Other Parts Discussed in Thread: DRV8711

Hi,

My customer is using DRV8711.
He has SPI issue at customer's board.
It is different in registers setting(writing) value and reading value.
This is the issue which rarely happens.

Now, I am confirming to customer to give me SPI waveform at issue.

Could you advice me about this issue, please?
Is there SPI caution of DRV8711 only?

Best regards,
Shimizu

  • 0
    TI__Mastermind 26065 points
    Hi Shimizu,

    A known issue I remember is that for the reserved bit 11 in 0x01 may not taken what you written in. Since it is on reserved bit with no function, it can be masked out by software when we do the read/write/verfy process of the SPI parameters.

    Best regards,
  • 0 in reply to Wilson Zuo
    Guru 11235 points

    Hi Wilson,

    Thank you for your support.

    I got waveform at this issue of TORQUE bit.
    Please see the attached file.

    Customer has issue at MODE bit and TORQUE bit.
    SPI speed is 3.4bps.

    Could you advice me the cause of this issue, please?

    DRV8711.pptx
    Regards,
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Mastermind 26065 points
    Hi Shimizu,

    Thanks of your waveform and marking. Is this happen all the time or just randomly. Did customer checked if using lower CLK frequency? I may need design team's help on looking at this issue. Anything related to the conditions triggering the issue would be help.

    Best regards,
  • 0 in reply to Wilson Zuo
    Guru 11235 points
    Hi Wilson,

    Thank you for your support.
    I will confirm about issue in lower clock frequency.

    This issue is just randomly.

    Thanks,
    Shimizu
  • 0 in reply to masahiko shimizu
    TI__Mastermind 26065 points
    Hi Shimizu,

    Also could you ask customer to check during the issue happening, from the behavior of the motor, whether the correct data is written in but only the DOUT is wrong? Because it is possible that only the buffer of the DOUT can't working stable at such high CLK.

    Also any zoom in waveforms of the clear CLK edge may be help to identify whether there is a noise issue of the SPI line.

    Best regards,
  • 0 in reply to Wilson Zuo
    Guru 11235 points

    Hi Wilson,

    Thank you for your support.

    Customer found this issue by motor behavior.
    Customer has this issue at MODE bit and TORQUE bit.
    MODE bit changes step. TORQUE bit changes full scale chopping current.
    For the this reason, customer noticed this issue immediately.
    After this issue, customer added read/rewrite program to MCU.
    I think cause of this issue is not Dout buffer from above.

    Also, This issue has at 1Mbps, too.
    Please the following picture.


    I will confirm about noise.

    Thanks
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Mastermind 26065 points
    Hi Shimizu,

    I think we can also try the read/write without the motor connected, so that there will be no current chopping noise. Then, we can see whether the issue happens with the same rate.

    Best regards,
  • 0 in reply to Wilson Zuo
    Guru 11235 points
    Hi Wilson,

    Thank you for your reply.
    I confirmed the below to customer.

    - One MCU is connected to three DRV8711s through SPI.
    - At first, This issue occurred only the 2nd DRV8711 in all DRV8711s(The 1st DRV8711 and the 3rd DRV8711 is normal writing).
    But After changing MCU soft ware, This issue occurred the only 3rd DRV8711 in all DRV8711s(The 1st DRV8711 and the 2nd DRV8711 is normal writing).
    　In Addition information, There is not changing of hard ware(circuit). Same layout,　
    - When DRV8711 operating motor(output PWM signal to motor), This issue occurs.
    - In case of writing TORQUE->CTRL, TORQUE is not set.
    - In case of writing CTRL->TORQUE, CTRL is not set.
    - Their register at which this issue is occurred can set normally by rewriting.
    - We think this issue is unrelated to a bit rate.
    -> 3.4Mbps, 1Mbps occurred
    - In case of operating without motor from DRV8711 at which this issue is occurred, This issue occurred, too.
    - When system start, All register is set by MCU. But this issue doesn't occur at this time.
    　
    During operating motor(output PWM signal to motor), Is there timing-like caution against writing register? In particular torque and step setting.

    Thanks
    Shimizu
  • 0 in reply to masahiko shimizu
    TI__Mastermind 26065 points
    Hi Shimizu,

    What changed when said "After changing MCU software" ? What is layout like? can we get a picture.

    Also, I'm a little concern that this may be a software issue.

    Best regards,
  • 0 in reply to Wilson Zuo
    Guru 11235 points

    Hi Wilson,

    Thank you for your support.
    I will confirm detail of changing soft ware and PCB Layout.

    About the below question, Is there caution?

    >During operating motor(output PWM signal to motor), Is there timing-like caution against writing register? In particular torque and step setting.


    Thanks
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Mastermind 26065 points

    Hi Shimizu,

    There is no any timing-like caution here. I'm working on some board with DRV8711 and actually I can change everything on the fly, such as current level(torque), decay modes, micro-stepping modes. Maybe there is noise affecting the SPI in customer board, so we need to check the layout. 

    Best regards,

  • 0 in reply to Wilson Zuo
    Guru 11235 points

    Hi Wilson,

     Thank you for your support.

     I understand the following.

     - There is no any timing-like caution about writing of MODE bit and TORQUE bit.

     - When you try to reproduce this issue, This issue did not occur at your bench.

    I don't send PCB layout to you. Please don't worry.

    Thanks,

    Shimizu