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BOOSTXL-DRV8323RS: can't spin motor on 1x PWM mode

Prodigy 180 points

Replies: 5

Views: 174

Part Number: BOOSTXL-DRV8323RS

Hi, I have a brushless DC motor from MOONS' (here is the link to the motor) and I am using the DRV8323 evaluation module to drive it. I have the EVM connected to an STM32 MCU, which I have written the SPI driver for per the DRV8323 data sheet spec. I have the INLC line high and the INHC line low. The hall sensors from the motor connect to DRV8323 through the five pin male header on the bottom edge of the EVM. I have a 10kHz PWM going into INHA with a 20% duty cycle. I have verified this on a scope. There is 24VDC being supplied to the EVM and a ground from the MCU. Upon powering the EVM, the motor draws current, but does not spin as it should not because its expecting hall inputs from the MCU. Upon issuing a SPI command to the MCU to change to the 1x PWM mode, the motor stops receiving current to any of it's phases and there are no faults. Here are the SPI comms:

Enable line is toggled high followed by a 1ms delay before all SPI comms.

Time [s] Analyzer Name Decoded Protocol Result
0 SPI MOSI: 0x1040 MISO: 0x0000
0.000098625 SPI MOSI: 0x8000 MISO: 0x0000
0.0002098125 SPI MOSI: 0x8800 MISO: 0x0000
0.000321 SPI MOSI: 0x9000 MISO: 0x0040
0.0004321875 SPI MOSI: 0x9800 MISO: 0x03FF
0.000543375 SPI MOSI: 0xA000 MISO: 0x07FF
0.0006545625 SPI MOSI: 0xA800 MISO: 0x0159
0.00076575 SPI MOSI: 0xB000 MISO: 0x0283

The first transmission is setting the DRV8323 to operate in the 1x PWM mode. The following lines are reading each of the registers Status 1, Status 2, and each of the 5 control registers. The 1x PWM mode did in fact take hold and each of the other registers returns what the power on default values should be per the data sheet. So I am not really sure why the motor is not getting power at all once the new PWM mode is applied. Thanks in advance for your help. Let me know if require any other information.

Kind Regards,

Sam

  • Sam,

    Above all looks correct to me. Have you tried the setup with the default kit launchpad to make sure the motor can spin with the kit before modification?

    Regards,

    -Adam
  • In reply to Adam Sidelsky:

    Adam,
    We did not purchase the launchpad controller for development. Is it possible that the electrical characteristics of our motor are somehow not compatible? The odd part for me is that under the power on default mode of 6x PWM mode, one of the phases in the motor is getting power and under the 1x mode, there is no power (ie. the current draw for the DRV drops to 20mA). It would be great to determine the cause of the error here without having to wait for admin to purchase/ship/etc the launchpad board, but if you think it's vital, we can do it.

    -sam
  • In reply to Samuel Petrocelli:

    Sam,

    Your halls are connected to J2 correct? Have you connected the hall power and Ground on J2 as well? What voltage is your hall power?

    Did you install R36, R37, and R38?

    Regards,

    -Adam
  • In reply to Adam Sidelsky:

    Adam,
    That was it. We needed to install those resistors. Now we need to figure out how to tune for this motor. Thanks for your help.

    -sam
  • In reply to Samuel Petrocelli:

    Sam,

    It is assumed that most people buy the BoostXL EVMs to connect to a launchpad which doesn't use the halls so those are disabled by default. Sorry for the confusion!

    Regards,

    -Adam

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