topic Re: How to initialize a DMA channel for a circular buffer? in Vybrid Processors

How to initialize a DMA channel for a circular buffer?

dieterfalk — Wed, 06 Aug 2014 11:59:00 GMT

I want to initialize a DMA channel to transfer input capture values (e.g. FTM2_CH0) to a circular destination buffer using the modulo feature. This DMA should run continuously. The buffer will be checked periodically (reading the DADDR register value to determine the current write pointer.

I am not clear about the initialization of the DOFF register and minor-/major loop operation register if I want to use the continuous running DMA with the modulo feature. Can you help me with an example code? Thank you.

Re: How to initialize a DMA channel for a circular buffer?

karina_valencia — Fri, 29 Aug 2014 16:19:19 GMT

timesyssupport can you help with this case?

Re: How to initialize a DMA channel for a circular buffer?

timesyssupport — Fri, 29 Aug 2014 19:47:47 GMT

Hello Dieter,

Are you looking to do this in MQX or Linux? Let me know, and I will see if there is any similar code available.

Thanks,

Timesys Support

Re: How to initialize a DMA channel for a circular buffer?

dieterfalk — Mon, 01 Sep 2014 04:59:10 GMT

Hello,

the code should be independent on any OS.

Dieter

Re: How to initialize a DMA channel for a circular buffer?

timesyssupport — Wed, 03 Sep 2014 18:07:01 GMT

Hello Dieter,

I have reviewed all Linux driver source for the Vybrid Tower that uses eDMA (serial, dspi, asrc, sound), but unfortunately, none of these use the eDMA modulo feature. karinavalencia, does the Freescale team have any input about how the DMAx_TCDn_DOFF, DMAx_TCDn_NBYTES*, DMAx_TCDn_BITER*, and DMAx_TCDn_CITER* registers should be configured when using the modulo feature of eDMA (bits 3-7 of DMAx_TCDn_ATTR set)? Dieter, feel free to clarify if this is not what you are looking for.

Thanks,

Timesys Support

Re: How to initialize a DMA channel for a circular buffer?

karina_valencia — Wed, 03 Sep 2014 18:13:40 GMT

rendy can you review previous update from Timesys and share your comments?

Re: How to initialize a DMA channel for a circular buffer?

rendy — Thu, 04 Sep 2014 10:56:16 GMT

Hi,

please try attached example code which should demonstrate using of DMA. Let me know in case of any problems. Project are created with IAR version 7.10, will not work withe lesser version. You can download 30 day trial here: http://supp.iar.com/Download/SW/?item=EWARM-EVAL

Rene

Re: How to initialize a DMA channel for a circular buffer?

dieterfalk — Fri, 05 Sep 2014 05:59:39 GMT

Hello,

thanks for these examples. They mainly show the general use of DMA in different examples. The modulo feature is not used.

In any case I think these example will help me to find a solution for my problem. Therefore I will close this task.

Dieter