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TMS320F28054M: How to reverse the direction for Inertia Identify

Qiang Guo
Expert 1695 points
Part Number: TMS320F28054M

In lab 5c - Inertia ID

I want to use negative direction for Inertia ID, what parameter do I need to change? 

  • 0
    Guru 12800 points

    SpinTAC Velocity Identify is only designed to run in the positive speed direction.  It does not support running in the negative direction.

    If you want the motor to spin in the opposite direction simply switch any two of the motor phase connections.  This will cause the motor to rotate the opposite direction but will still regard it as the positive direction.

  • 0 in reply to Adam D. Reynolds
    Expert 1695 points

    HI Adam,
    I did few tests about the direction. If I only switched any of two motor phase connections, it would cause my motor not run properly and overheating my motor in few seconds.
    But if I switched any of the two motor phases AND switched encoder QEPA and QEPB connections as well. Then motor can run in opposite direction without any problem.
    I am not quite sure why...

    Since I don't want to changed my hardware wire connections, so I tried to switched QEPA-GPIO20 and QEPB-GPIO21 in hal.c.  and it doesn't work.

  • 0 in reply to Qiang Guo
    Guru 12800 points

    Qiang Guo said:
    But if I switched any of the two motor phases AND switched encoder QEPA and QEPB connections as well. Then motor can run in opposite direction without any problem.
    I am not quite sure why...

    The motor and encoder need to have the same notion of positive rotation.  This is typically defined as:

    1. Motor rotates anti-clockwise when looking at end of motor shaft (this implies that the motor phases are in the correct order)

    2. Encoder channel A is leading channel B

    So if you change any two motor phases so that the motor shaft is rotating clockwise, you will also need to swap the encoder phases so that the MCU perceives channel A is leading channel B.