Event-based buffer transfer from M4 to permanent file in A7 Linux fs

[YChen.12]

Hi,

I have a firmware doing permanent acquisition and processing of a signal coming from SPI on the M4 side - consider it an audio stream.

On-demand I would like to save the processed buffer (say ~10 consecutive buffers once in a while, e.g. 1s every 10s) from the SRAM to a permanent file accessible from the A7 Linux userspace.

What would be the best way to do this with the least impact on the M4 load ?

My first guess was DMA from SRAM to DDR and then have Linux write from DDR to eMMC/SD but isn't there a more direct way ?

Thanks a lot

Yann

[Kevin HUBER]

Hello @YChen.12​ ,

I understand that you want to store data in A7 side that are coming from M4 side.

Please look at this demonstration application: https://wiki.st.com/stm32mpu/wiki/How_to_exchange_data_buffers_with_the_coprocessor

This page explains how it is possible to send large data between the processors and it details two methods.

Since you are sending audio, I think the best method for your case is the one with large buffer in DDR. The one with rpmsg_sdb driver (RPMsg shared data buffer):This method must be used when the Data flow sampling frequency is more than 5 MHz.

By following the page, you are able to realize some tests with the logicanalyser application

Regards,

Kevin

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