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BOOST-DRV8711: SPI read and Write not working properly when ENBL is set to 1 in CTRL Register.

Rohan Kumbhar
Prodigy 30 points
Part Number: BOOST-DRV8711
Other Parts Discussed in Thread: DRV8711

Tool/software:

Hi, I am using STM32H755ZI controller to work with BOOST-DRV8711. Currently what I am doing is read the default values in the register and then modify the required bits and read back to check if values are set properly.

We observed that when ENBL bit = 1 and motor is connected to BOOST-DRV8711. We saw those values what we set are not matching most of the time, but when we carried out same experiment just this time we have not connected motor we were getting same value what we have set. Currently we are suspecting EMI issue, but we would like to know if there is anything that can cause this issue?

Also we found that when we set DECMOD to 5 i.e Auto decay mode we found that SPI read and write was causing more issue. currently we have set it to 1 where we see SPI read write issues are less 

G_CTRL_REG.ISGAIN = 0;

G_CTRL_REG.MODE = 7;

G_CTRL_REG.ENBL = 0;

G_TORQUE_REG.SIMPLTH = 1;

G_TORQUE_REG.TORQUE = 100;

G_DECAY_REG.DECMOD = 1;

G_STALL_REG.SDCNT = 3;

G_STALL_REG.VDIV = 3;

G_STALL_REG.SDTHR = 0;

  • 0
    TI__Mastermind 44595 points

    Hi Rohan,

    Thanks for reaching out to us via this forum.

    Rohan Kumbhar said:
    We observed that when ENBL bit = 1 and motor is connected to BOOST-DRV8711. We saw those values what we set are not matching most of the time, but when we carried out same experiment just this time we have not connected motor we were getting same value what we have set. Currently we are suspecting EMI issue, but we would like to know if there is anything that can cause this issue?

    No other known reason that can cause this issue. You may be using long loose wires for SPI and GND connection forming delays and/or cross talk. You can double check with these. What is the SPI clock speed used? Can we get logic analyzer or scope captures of SDO, SDI, SCLK and SCS signals? Make sure all the power rails especially 3.3 V rails have proper supply.

    Rohan Kumbhar said:
    Also we found that when we set DECMOD to 5 i.e Auto decay mode we found that SPI read and write was causing more issue. currently we have set it to 1 where we see SPI read write issues are less 

    SPI transaction must not be impacted by DECMOD, Auto decay mode is the recommended setting. Be sure to have proper TOFF configuration. Can you share the coil current waveforms using a current probe? Thank you.

    Regards, Murugavel 

  • 0 in reply to Murugavel4637
    Prodigy 30 points

    Hi Murugavel,

    Thanks for the quick reply, we are using currently jumper wires to interface DRV8711. We will try to make proper setup and check if the issue still persists. I cannot provide you the coil current waveform due to unavailability of current probe.

  • 0 in reply to Rohan Kumbhar
    TI__Mastermind 44595 points

    Hi Rohan,

    Okay thank you.

    Regards, Murugavel