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DRV8899-Q1: Home state in non-circular 1/2 step

Yuto Kitamura
Expert 6695 points
Part Number: DRV8899-Q1

Tool/software:

Dear team,

1. Would I know the home state in non-circular 1/2 step mode?
In 1/8, 1/4, 1/2 and full-step mode, it is defined as 45 deg.@electrical angle as shown below.

2. Also FULL STEP 100% is also 45 deg? It is not defined clearly neither on the datasheet.

Best regards,
Yuto Kitamura 

  • 0
    TI__Expert 5340 points

    Hi Yuto, 

    Yuto Kitamura said:
    1. Would I know the home state in non-circular 1/2 step mode?

    The home state is an electrical angle of 45°. Under the Noncircular mode AOUT, 100%, BOUT 100% is home state. 

    Yuto Kitamura said:
    Also FULL STEP 100% is also 45 deg? It is not defined clearly neither on the datasheet.

    Yes, it is also 45 deg.

    Please let us know if you have any more questions. 

    Best regards, 

    Mojtaba. 

  • 0 in reply to Mojtaba Afshar
    TI__Expert 6695 points

    Hi Mojtaba,

    Thanks for quick respond and that makes sense.

    Additional relative question about to obtain the electrical angle information. Can DRV8889 or DRV8899 get the electrical angle information?
    I think we can estimate it on software by calculating from # of STEP input, DIR, microstep setting and do surplus by maximum STEP number (= 4 when full step mode). But Rohm: BD63800 seems be able to directly obtain the electrical angle by reading "MSP[6:0]" register.

    Best regards,
    Yuto

  • +1 in reply to Yuto Kitamura
    TI__Expert 5340 points

    Hi Yuto, 

    Thanks for your question. 

    With drivers such as the DRV8899-Q1 there is no feedback on the indexer position. To understand the exact electrical angle it can be derived by the MCU keeping track of the number of steps sent to the driver.

    Example: Let's assume a stepper is driven with 1/8 step mode. The current waveform will resemble like shown below. One quadrant of the current sinewave will have 8 steps and one full cycle of sinewave will have 32 steps which would be 360 ° electrical angle. One step (mircostep) would be 360 / 32 = 11.25 ° electrical angle.

    Best regards, 

    Mojtaba