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F28M35H52C: EQAP- T method speed peaks

Max Altrichter
Prodigy 10 points
Part Number: F28M35H52C


Hey all,

I am trying to implement a speed measurement via EQEP- T Method. Unfortunately i got some peaks at my signal that i cant eliminate. I capurted "QEPSTS.bit.UPEVNT, QEPSTS.bit.COEF and QCPRDLAT" . It turns  out that the peaks only occur when the follwing scenario happens:

- low speed, almost 0. COEF==1 and speed=0

- now i turn the motor shaft so slow that the register still detacts a overflow

- now i turn a tiny little bit faster

- at some point the COEF flag gets 0 and the speed calculation will get me a peak because at the QCPRDLAT register is a invalid value ( something very small, it seems that the register got an oveflow)

It seems like there is a old value lachet in QCPRDLAT or COEF isnt set properly.

Any Ideas? Any help would be great :D

Best regards,

Max

  • 0
    TI__Mastermind 45606 points

    Hi Max,

    How about the QEPSTS[CEDF] and [PCEF] error flags? Are either being set in your case? This could mean that a direction change has occurred between position capture events.

    Max Altrichter said:
    - at some point the COEF flag gets 0 and the speed calculation will get me a peak because at the QCPRDLAT register is a invalid value ( something very small, it seems that the register got an oveflow)

    What event are you latching the QCPRDLAT register on? A unit timeout or a read of the eQEP position counter (QPOSCNT)?

    Best,

    Kevin