RM57: Circular buffer with DMA

Gunter Schmer

Other Parts Discussed in Thread: RM57L843

Hi,

This is for an RM57L843. I saw a couple posts with e2e on Hercules circular buffers with DMA and will review those. But I wanted to post the specific question from a customer:

We were unable to configure the DMA so that it fills a circular buffer that we occasionally drained. The attempt we made was to read the CTCOUNT register when we were ready and drain the buffer, but because CTCOUNT isn't updated until the DMA is arbitrated out of the priority queue, this didn't appear to work. Is there a way to use this DMA in this fashion? Maybe a way to force an update of CTCOUNT without interrupting an in-progress DMA transfer?

Is there a better way of doing this with the DMA?

Thanks,

--Gunter

over 8 years ago

0 Charles Tsai over 8 years ago

TI__Guru**** 191296 points

Gunter,
There are a few posts asking the same question. As you and your customer are already aware of, the CTCOUNT isn't updated until the DMA is arbitrated out. If you check those posts, recommendation was given to add dummy channel so that will force the DMA to arbitrate and as a result saving back the current context back to the working control packet.

0 Gunter Schmer over 8 years ago in reply to Charles Tsai

TI__Genius 14212 points

Hi Charles,

thanks for this. Regarding using the dummy DMA channel to arbitrate primary DMA channels out of the arbitration queue, we are looking at the following thread

Please let us know if there are other good threads.

Regards,

--Gunter

0 Charles Tsai over 8 years ago in reply to Gunter Schmer

TI__Guru**** 191296 points

Hi Gunter,
I also find this post helpful shared by our community member Joe. The post was an old post but last updated by Joe on Sep 15, 2016.

e2e.ti.com/.../1978855

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RM57: Circular buffer with DMA