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Driving a Stepper Motor with the CPG004_DRV8812 EVM

Naji Naufel
Intellectual 805 points
Other Parts Discussed in Thread: DRV8812, DRV8824, MSP430F1612, DRV8829, DRV8828, DRV8825, DRV8802, DRV8812EVM

Hi,

 

I have a DRV8812 EVM with which I am trying to drive a bi-phase stepper motor. I am assuming that I would have to sequence the Phase pins in the correct order manually to see the motor rotate.

Is there any control in the GUI that will spin the motor for me?

Is there a reference design for the on-board MSP430 that spins a stepper motor? Is the code that comes on the CD it?

Am I better off getting a DRV8824/25 EVM? Would it spin a motor for me via a GUI button?

  • 0
    TI__Expert 7455 points

    Hi Naji,

    The DRV8812 EVM software has a section called stepper demo which shows an earlier version of the high resolution microstepping application note by modulating the VREF terminals throughout the MSP430F1612 dual DAC outputs. If you press on Start Steps you should see the stepper motor moving in one direction. You can specify speed on the provided text box and direction by clicking on the check box.

    That being said, I am working a new firmware release in which the EVM will offer more control and up to 512 degrees of microstepping by following the same technique. it will have a better interface and allow for much more control such as acceleration profiles, S Curve acceleration, Motion in Steps, etc. The DRV8828 and DRV8829 EVM will be released with all of these features.

    If you want to control a stepper with the least amount of effort, the DRV8824 and DRV8825 are always the better choice. DRV8812 will require some code to get the stepper to move and are only meant for applications requiring much more than 32 degrees of microstepping. If all you want is speed control, direction control and microstepping with up to 32 degrees of resolution, then there is no reason to prefer the DRV8812/13 over the DRV8824/25, unless you already have some code around this topology an you do not want to recode.

    Hope the info helps. Best regards,

    Jose Quinones

  • 0 in reply to Jose Quinones
    Intellectual 805 points

    Hi Jose,

     

    Thank you. It worked.

    Why is it that when I change the PWM setting to any number other than 0, the stepper motor stops spinning?

    Naji

  • 0 in reply to Naji Naufel
    TI__Expert 7455 points

    Hi Naji,

    When driving the stepper, I would not touch anything else on the other section of the tab as the EVM is just executing a demo subroutine and it would be removed from that loop.

    When I designed this EVM, the DRV8812/13 was intended to drive either 2 DC motors or a stepper motor. The EVM software was designed so you could evaluate the signals on a 1 by one basis, not necessarily to be able to tackle either application fully.

    Eventually we figured out it was better to optimize the DRV8812/13 for stepper usage and the DRV8802/14 for DC motor usage. This is why I am working on an enhanced EVM for the stepper version. Something that will allow you to treat the EVM as a stepper controller, not just a dual H Bridge. At the moment, however, it is kind of crude as a stepper driver, so I must apologize for my lack of vision on that front. I promise the next version will look way much more cool!

    Glad the stepper is moving, though.

    Best regards,

    Jose Quinones 

  • 0 in reply to Jose Quinones
    Intellectual 805 points

    I will be interested in giving this new software a test drive when it is ready. Would you please let me know when it is available?

     

    thank you

    Naji

  • 0 in reply to Naji Naufel
    TI__Expert 7455 points

    Naji, Definitely!

    If you have the capability to reflash the EVM (you will need one of the MSP430 FET UI modules to do so), please feel free to contact me at jquinones@ti.com and I'll get you equipped with a superior version.

    Best regards,

    Jose Quinones

  • 0 in reply to Jose Quinones
    Intellectual 805 points

    Hi Jose,

    Do you have any App Notes or white papers on measuring the BEMF of a stepper motor to see if it encountered a hard stop?

    Naji

  • 0 in reply to Naji Naufel
    TI__Expert 7455 points

    Hi Naji,

    At the moment I do not have anything to offer on this topic. I am studying different algorithms to explore how to close the loop around a stepper either by the usage of a sensor or through a sensorless endeavor. However, at the moment I do no have much information to offer on either. Sorry!

    Best regards,

    Jose Quinones

  • 0 in reply to Jose Quinones
    Prodigy 140 points

    Hi Jose,

    I am currently working on DRV8812EVM as well. After downloading the FW(CPG004_RB_MSP430F1612_Firmware_LMD_TI) that you developed into MCU and run the windows application, I can not manage to make the stepper run while following procedures you described here. 

    Note that the connection is not a problem as I can set the reference voltages with the software coming with the kit. Please let me know if you have any thought on this issue. Thanks in advance!

    -Sean

  • 0 in reply to Jose Quinones
    Prodigy 140 points

    BTW:

    The stepper motor I am using is wo-211-13-02 from Lin Engineering with inductance 1.1mH/Phase

    VM is 12v.

    Through it seems to me that they should be any problem

    -Sean

  • 0 in reply to Jose Quinones
    Prodigy 140 points

    Hi Jose,

    There is one thing I found out: when clicking "start steps"  in the CPG004 DRV88xx  EVM software, I should have been seeing square waves for Phase A/B, non negative sine waves for Vref A/B, and high level for Ena A/B.

    However when I use my oscilloscope for testing, I am able to observe a high voltage level for Enable A/B. Phase A/B and Vref A/B remains at low voltage level.

    Is the Firmware designed to be so?

    -Sean