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Original question:

DRV8825: Erratic behaviour of stepper motor

DRV8825: DIR pin not working consistently

collin pernu
Prodigy 20 points
Part Number: DRV8825

Hi,

I am using a DRV8825 in a project and having some issues with the DIR pin not actually changing direction when pulled high or low. I have a script that moves the motor, stops it, and changes direction to move again. When the DIR pin is pulled high or low(verified by oscilliscope), the direction it steps will sometimes not change and sometimes will change. I tried replacing the component after verifying correct inputs and it still moves randomly. schematic included below, let me know if you have any ideas!

  • 0
    TI__Genius 15405 points

    Hi Collin,

    Do you have any current limiting resistors or filter capacitors between your DRV control pins (DIR) and your microcontroller that aren't shown?
    Your C4 Capacitor should be a 0.1-μF not 0.01uF. I'd try changing that first.
    What VM voltage are you running at?

    What is your microstep setting when the DIR pin isn't working? does it behave the same at high speeds and low speeds?

  • 0 in reply to Yara Al Shami
    Prodigy 20 points

    Hi Yara, 

    Thank you for your response. There are no limit resistors or filter caps between MCU and DRV. 

    VM = 16V

    I have tried all microstep configurations and speeds of 100-500 and this issue still occurs in all

    Swapping out the capacitor, the issue is still there, with a reading of 28V on VCP if that is of any importance.

    I also swapped out the DRV to see if something about C4 burned it up, and still no success.

    Thanks!

  • 0 in reply to collin pernu
    TI__Genius 15405 points

    Hi Collin,

    Is it possible to get some screenshots of your waveforms? And voltage readings from the DIR pin?

    How does the device behave if you were to eliminate the "stop" in your script and just have it change direction while it spins? Or eliminating the script completely and just supplying a STEP and DIR signal since the logic is hard coded?