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DRV8711: motor on HOLD position

Benny Rabin
Prodigy 50 points
Part Number: DRV8711
Other Parts Discussed in Thread: DRV8704,

How to turn "holding torque" on and off? When I stop the motor, I can not force holding current. Is it possible in PWM mode only?

  • 0
    TI__Guru 56650 points

    Benny,

    How do yo stop the motor? If you just stop sending a rising signal to STEP pin (Indexer mode pin: Rising edge causes the indexer to move one step), the motor winding would keep the current and holding the torque.

  • 0 in reply to Wang5577
    Prodigy 50 points

    Hello Wang Li, thank you for the response.

    The chip does not response as you describe, and it does strange things like: when sending single step command via the SPI, it start the motor continuously,  even when the  SPI communication stopped.

    I think that I should replace the chip and check again. It might be defective.

    Benny

  • 0 in reply to Benny Rabin
    TI__Guru 56650 points

    Benny,

    BTW, what motor do you test? Stepper motor or brushed DC motor. If you work on a brushed DC motor, you can check the DRV8704.

    "when sending single step command via the SPI,  it start the motor continuously" What SPI command (register address and value) do you send to DRV8711?

  • 0 in reply to Wang5577
    Prodigy 50 points

    Wang5577 said:

    Benny,

    BTW, what motor do you test? Stepper motor or brushed DC motor. If you work on a brushed DC motor, you can check the DRV8704.

    "when sending single step command via the SPI,  it start the motor continuously" What SPI command (register address and value) do you send to DRV8711?

    I am using stepper motor. SPI command: CTRL register (0x00) data (incl. address) = 0x0C015 (MSB first)

    Benny

  • 0 in reply to Benny Rabin
    TI__Guru 56650 points

    Benny,

    C015H= 1100 0000 0001 1001 b

    "when sending single step command via the SPI,  it start the motor continuously"

    So, after you enable the motor drive output. And the motor continuously runs. This is normal, right?

  • 0 in reply to Wang5577
    Prodigy 50 points

    According to the datasheet, setting the RSTEP bit shoulde advance the motor 1 STEP, and the RASTEP bit cleared automatically - that means that the motor should increment 1 step and DO NOT run continuously.

    Anyhow, I am replacing the chip right now, as I want to see if it is a chip problem. Will send an update after testing.

    Thank you

    Benny

  • 0 in reply to Benny Rabin
    TI__Guru 56650 points

    Benny,

    Thank you for your update. Yes.  RSTEP bit shoulde advance the motor 1 STEP, and the RASTEP bit cleared automatically.

    Also, we have to make sure no pulses on STEP pin.

  • 0 in reply to Wang5577
    Prodigy 50 points

    Thank you for the support.

    It took me time, but I found the reasons for the strsnge functionality:

    1) I have to setup the SPI sump on falling edge and NOT rising edge, as written in the manual. SPI communication started working good with the falling edge sttings.

    2) Internal PWM has poor performance. Consequently, I had to lower the supply voltage, as I could not get to the torque I need with high input voltage. I can do it only with external PWM mode.

    Same problem while working with small microstep.

    It's a pity that I can't control the PWM frequency, I assume that it will solve the problem.

    At least I have something working :-) thanks again.