am335x (beaglebone) eQEP CDEF flag error

Vasileios Tsounis

Hi,

I have been using the eQEP modules in the beaglebone's Sitara to conduct motor speed calculations and during various tests I have noticed that the CDEF (capture direction error flag) does not appear to work at all.

To clarify what I mean, I have done extensive testing of this module, running position control algorithms and logging the values for the QEPSTS register in each control loop iteration. At the same time, I have enabled an interrupt service routine that also logs the occuring interrupt events.

What I have noticed is that while the interrupt for the QDC (quadrature direction change) fires and indeed recognizes changes in the DIR signal, CDEF has never been enabled.

As the TRM states, for a value in the QCAPRD register to be valid no overflow or direction change must occur (COEF and CDEF have to be set), but how can the QDC interrupt occur and the CDEF not be set?

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Vasileios,

What software are you running?

0 Vasileios Tsounis over 12 years ago in reply to Biser Gatchev-XID

Prodigy 190 points

Hi Biser,

Thank you for the replay.

I am running my own code based on the Starterware HAL (v2.00.00.07), and I wrote my own driver for the eQEP module since there is none in Starterware. I based it on the structure that almost all other peripheral drivers have, just like the ePWM driver. The module works just fine, I can get really accurate position and speed data, but this CDEF flag does not seem to activate even thou the QDC interrupt fires.

Kind regards,

Vasileios.

0 Biser Gatchev-XID over 12 years ago in reply to Vasileios Tsounis

TI__Guru**** 393215 points

Hi Vasileios,

Can you check if you have a read-modify-write operation on the QEPSTS Register? This could possibly clear the CDEF, because when set it gets cleared by writing 1 to it.

Other than that for Starterware questions there is a dedicated forum: http://e2e.ti.com/support/embedded/starterware/default.aspx

0 Vasileios Tsounis over 12 years ago in reply to Biser Gatchev-XID

Prodigy 190 points

Hi again,

I do but not exactly. I save the status to a static variable and return that from the function that implements the algorithm. If the value for that bit is set in the QEPSTS, and so also in the variable, then I write 1 to that bit in the register to clear it. So by saving the value, if it had been set at all, that event would not be affected by any subsequent writes to the register.

My issue is with the functionality and internal signaling through which the events are generated (bits are set). One thought I had is that maybe by enabling the interrupt then the bit is never set, but I have also tried this and it does not seem to have any effect.

0 Biser Gatchev-XID over 12 years ago in reply to Vasileios Tsounis

TI__Guru**** 393215 points

I have notified the factory team about this. Let's see what they can say. I will update this thread once I receive some information.

0 Daniel Haslimann over 10 years ago

Intellectual 810 points

Hi Vasileios

Would you be willing to share your QEP module? That would be of great help!

Thanks,

Daniel

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am335x (beaglebone) eQEP CDEF flag error