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Using External Signals On the DRV8850EVM Board

Charles Fleck
Prodigy 100 points
Other Parts Discussed in Thread: DRV8850EVM

Hey,

I have a DRV8850EVM board and am trying to use the external signals (IN1H, IN1L, IN2H, and IN2L) to control a motor. All I could find in the datasheet that I needed to do was to remove resistors R5-R8 and then it should work, but for some reason my output signals are both always held low regardless of what I input. To run the motor forward I have been trying to input PWMs on IN1L and IN1H while I hold IN2L high and IN2H low. I tried switching these signals around, but to no avail. Is there something else that I should be doing to allow the external signals to work? Or is it possible that I am trying to control the signals incorrectly? Any help would be much appreciated.


Thank you!

Charles

  • 0
    TI__Genius 12485 points

    Charles,

    Moving this to the Motor Driver forum..

    Regards,

    Gautham Ramachandran

    Apps. Engineer- Haptics

  • 0 in reply to Gautham
    TI__Guru** 114905 points

    Hi Charles,

    I am assuming the board was operating correctly prior to removing the resistors. Is that correct?

    There are a couple of items to check.

    First, please confirm the device is awake. You can do this by looking for 3.3V on JP1 pin 1. If 3.3V is not there the device is not awake. Press switch S1 and check again. 3.3V should now be available and the device is awake. If not, the device is suspect.

    Next is the inputs on IN1L and IN1H. I am assuming you are running the PWM signal on IN1H only and holding IN1L low. This condition will produce an output high on OUT1. Please try this and report what you find.

    If you are still seeing problems, I suggest you disconnect the motor and focus on the two outputs separately. By controlling the INxL and INxH, you can how the output is reacting statically. Connecting the midpoint of a resistor divider from VCC to GND to create 2 to 3V at the output allows a quick check of the output states.  

  • 0 in reply to Rick Duncan
    Prodigy 100 points

    Hey Rick,

    Sorry I never got around to updating this, but I solved the problem a while ago. I was using PSOC 4 Creator to create a control register to define my GPIO pins. For some reason the pins weren't correctly toggling when I tried to switch them. I'm assuming they needed a pull-up resistor or something and that the MSO was acting like one when it was attached - hence me reading the proper signals with it but it not working properly. I ended up removing the control register and just defining the pins individually as output pins and it worked.

    To move the motor I have two output pins connected to PWMs (IN1L and IN2L) and two defined as GPIO pins (IN1H and IN1L). To rotate the motor forward I set it to:

    IN1H high

    IN2H low

    IN1L low

    IN2L PWM

    To move the motor backwards I set it to:

    IN1H Low

    IN2H high

    IN1L PWM

    IN2L low

    Hopefully this helps someone out!

    Thanks.

    Charles