Kinetis Software Development KitのトピックRe: Is it possible to transfer from SPI to SAI using DMA?

Is it possible to transfer from SPI to SAI using DMA?

javiercardona — Tue, 10 Jan 2017 06:12:51 GMT

Hello,

Our KL27-based design has a codec connected via SAI (I2S) and a flash memory connected via SPI.

We are able to transfer audio buffers from/to the codec to/from flash using DMA transfers to/from SRAM.

We are now attempting to configure DMA to do direct transfer from I2S to SPI so we can record audio to flash with minimal CPU intervention.

Has anyone attempted this before? Just knowing that it is possible would be very helpful. Example code would be grand

Best,

Javier

Manuel Rodriguez Adrian Sanchez Cano

Re: Is it possible to transfer from SPI to SAI using DMA?

xiangjun_rong — Tue, 10 Jan 2017 09:13:17 GMT

Hi, Havier,

As you said that you are able to transfer data from SRAM to SPI flash via DMA, if it is the case, I think it is okay to transfer from I2S received data register to SPI data register via DMA.

The DMA itself supports to transfer data from peripheral to peripheral, but as you know that the I2S is stream data, I have two concern that the SPI itself is fast enough to transfer data so that the SPI module can keep up with the step of I2S, secondly, I am not familiar with the writting SPI flash, do you means that writing the SPI flash is to write the data to flash RAM, the flash itself has a state machine to write data from RAM to flash?

Xiangjun Rong

Re: Is it possible to transfer from SPI to SAI using DMA?

javiercardona — Wed, 11 Jan 2017 23:04:59 GMT

Hello Xiangjun,

Thanks a lot for your response.

Yes, I am capable to transfer data from/to SRAM to/from SPI as well as from/to SRAM to/from I2S using DMA.

When I try to configure the DMA channel for SPI to/from I2S (always triggered by I2S), I get a Bus Error on Source (DMA_DSR_BCR bit 29) when transferring from SPI, and a Bus Error on Destination (DMA_DSR_BCR bit 28). Would that be what you meant by "SPI module not keeping up with step of I2S"?

Thanks!

Javier

Re: Is it possible to transfer from SPI to SAI using DMA?

javiercardona — Wed, 11 Jan 2017 23:07:39 GMT

By the way, I should mention that the SPI Flash device that we are using is fast enough to accept data from the codec at the rate that it produces it (8 kHz). We are able to transfer data from SRAM to flash at 12 MHz SPI rates.

Cheers,

Javier

Re: Is it possible to transfer from SPI to SAI using DMA?

javiercardona — Thu, 12 Jan 2017 20:00:47 GMT

I solved the bus error problem by setting the Destination Size in the DMA DCR register to 8-bits when writing to SPI.

This solves the dma bus error and the DMA transfer completes successfully.

I do not observe any data on the SPI bus, but I will create a separate question for that.