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DRV8825: At micro stepping level of 3200 steps & 6400 steps. The DRV 8825 is jumping 0.9 deg.

sagar pai
Prodigy 30 points
Part Number: DRV8825

This is not my plot. But i have attached it as i see a similar behaviour

  • 0
    TI__Guru 56650 points

    Sagar,

    What do you mean "At micro stepping level of 3200 steps & 6400 steps"? Micro step setting is from full step to 1/32 step.

    What is the micro-step setting? Is this issue related to the motor speed? Can you show me the winding current?

  • 0 in reply to Wang5577
    Prodigy 30 points

    Sorry for the confusion. My bad. My motor is 1.8deg/full step or 200steps/rev.  I meant micro-stepping level of 1/16  leading to 3200 steps/rev,  and  micro-stepping level of 1/32 leading to 6400 steps/rev.

    The DRV8825 started to respect the micro-steps after i switched to fast decay. ( I was using mixed decay ). Can the decay be adjusted during operation from the micro-controller for the DRV8825. I would like to use the slow/mixed decay when the micro-stepping is not critical and shift to fast decay when the motion is critical.  If this is so, how i can shift to mixed decay ?

  • 0 in reply to sagar pai
    TI__Guru 56650 points

    Sagar,

    Yes. You can adjust the decay mode by setting different decay mode pin voltage during the operation. The new decay mode setting will be started on next PWM cycle.

    "The DRV8825 supports three different decay modes: slow decay, fast decay, and mixed decay. The current through the motor windings is regulated using a fixed-frequency PWM scheme. This means that after any drive phase, when a motor winding current has hit the current chopping threshold (ITRIP), the DRV8825 will place the winding in one of the three decay modes until the PWM cycle has expired. Afterward, a new drive phase starts."