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DRV8849: How to configure the pins of drv8849 to make the motor rotate?

Annie Liu
Genius 10295 points
Part Number: DRV8849

Hi Team,

The customer uses DRV8849 to drive a motor, and the OUT1A, OUT1B, OUT2A, and OUT2B outputs control a motor. 

Raise the following pins:

ENABLE1, ENABLE2 ,

NSLEEP

STEP1 and STEP2 

MODE01 and MODE11

VREF1 and VREF2

But the motor didn't rotate and kept getting hot. He used a multimeter to measure that the output was 5v. 

How should he configure the pins of drv8849 to make the motor rotate?

Regards,

Annie

  • 0
    TI__Mastermind 19740 points

    Hi Annie,

    I have a couple questions about the setup in order to further understand this issue. 

    When the pins are raised high, are they all being set to logic high (3.3V or 5V)? 

    What is the VREF1 and VREF2 voltages for current regulation?

    What is the STEPx input frequency?

    Best,

    David

  • 0 in reply to David Medis
    TI__Genius 10295 points

    Hi David,

    David Medis said:
    When the pins are raised high, are they all being set to logic high (3.3V or 5V)? 

    They are set to high level 3.3V.

    David Medis said:
    What is the VREF1 and VREF2 voltages for current regulation?

    VREF1 and VREF2 are 1.8V.

    David Medis said:
    What is the STEPx input frequency?

    Customer sees that the two pins step1 and step2 can only be pulled high or low.

  • 0 in reply to Annie Liu
    TI__Mastermind 19740 points

    Hi Annie, 

    The DRV8849 integrates an "indexer" with adjustable microstepping. The device can be configured in full-step to 1/256 microstepping.

    At each rising edge of the STEP input the indexer travels to the next state in the table. The direction is shown with the DIR pin logic high. If the DIR pin is logic low, the sequence is reversed.

    Best,

    David

  • 0 in reply to David Medis
    TI__Genius 10295 points

    Hi David,

    Does customer need to set the timing of STEP and DIR in the software? How to set it up?

    Regards, Annie

  • 0 in reply to Annie Liu
    TI__Mastermind 19740 points

    Hi Annie,

    Yes, an external microcontroller is required to send the step pulse. I would recommend looking at our DRV8849EVM which has the firmware files available for evaluation purposes. 

    Best,

    David

  • 0 in reply to David Medis
    TI__Genius 10295 points

    Hi David,

    Now the motor can rotate, but it's getting very hot. Customer would like to know how to solve it?

    Does it mean that in a certain mode, the frequency of fstep must be calculated by the following formula?

    The specific operations are as follows:

    Motor 1:

    MODE01 pull down MODE11 disable -----Configure mode to 1/32

    ENABLE1 Pull high nSLEEP Pull high ---- Turn on the motor

    According to the example in the datasheet, the frequency of STEP is 5KHZ. This step uses PWM signal operation, the frequency is 5KHz and the duty cycle is 50%. 

    Finally, the PWM signal is repeatedly switched on and off.

    Regards,

    Annie

  • 0 in reply to Annie Liu
    TI__Mastermind 19740 points

    Hi Annie,

    The step frequency, fstep, sets the speed on the stepper motor and the microstepping level sets the number of micro-steps for the motor. If the application requires a certain motor speed, the desired micro-steps can be used to calculate the frequency needed to obtain said speed and this frequency would be used for the PWM signal into the STEP pin. 

    Best,

    David