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DRV8818: step input and output

shshin
Prodigy 70 points
Part Number: DRV8818


Hi, all 

I try to control the step motor using drv8818.

Question 1.

  - When I put pulse on the STEP input pin, do I have to give it at 5V?

  - It is currently connected to ST company's MCU pin, and the corresponding MCU VCC  is 3.3V.

Question 2.

  - Are the output waveforms of the AOUT1, AOUT2, BOUT1, and BOUT2 pins normal?


Yellow = AOUT1, Blue = AOUT2, Red = BOUT1, Green = BOUT2

the motor does not rotate and only vibrates.

I ask for help. Let me know if you need any additional information

Best regards, 
Seong Hyu Shin.

  • 0
    TI__Mastermind 47815 points

    Hi Seong Hyu,

    Thank you for your post. I address the questions in the same order as you posted.

    1. This depends on the logic supply connected to Vcc pin of the DRV8818. See below snippet from the datasheet. It should be connected to MCU VCC for supporting this 3.3 V logic level. In the schematic VCC is 5V which translates to 0.7 x 5 = 3.5 V for minimum high input value. This should be fixed.

    2. The waveforms look normal to me. But I cannot say for sure what was going on because the conditions under which these waveform were captured are unknown to me. It is normal practice to measure each phase current and capture waveform using a current probe for the oscilloscope. Voltage outputs may just show chopping of the current regulation. Could you please get coil current waveform captures?  Also we need information IFS setting, microstep mode used, STEP rate etc. 

    3. See comment in #1. If Vcc is changed to 3.3 V then the VREF voltage dividers must also be changed accordingly. I see those resistive dividers are connected to the Vcc.

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    Prodigy 70 points

    Hi Murugavel.

    Thank you for your quick reply.

    I've solved this problem. 

    I raised the voltage of pulse on the step input side, and it was solved.

    Thank you for your help.

    Have a nice day~