SPIS DMA Setup Slow

RE: SPIS DMA Setup Slow

Jørgen Holmefjord — Thu, 08 Jun 2017 10:59:04 GMT

Do you have logging enabled? This could slow down the function.

RE: SPIS DMA Setup Slow

Christopher — Wed, 07 Jun 2017 17:20:34 GMT

I updated my post with the last findings. I ran the provided SDK 13 SPIS example, and checked the output on the scope.

RE: SPIS DMA Setup Slow

Jørgen Holmefjord — Wed, 07 Jun 2017 09:20:26 GMT

How do you measure this? This is my results from toggling a pin and checking with a logic analyzer: spis_buffers.png. I tested with different buffer sizes, but no change. Could you try the SPIS example directly, to see if there is any change?

RE: SPIS DMA Setup Slow

Christopher — Tue, 06 Jun 2017 16:08:57 GMT

I am still seeing 19.96us. I am checking this right after the nrf_drv_spis_init() call. I initialize the SPIS, and then call nrf_drv_spis_buffers_set(). I do not see 7us. I even tried using 32 Bytes instead of using the MAX 255 Bytes. No change. Are there any shortcuts? I am also running SDK 13.

RE: SPIS DMA Setup Slow

Jørgen Holmefjord — Tue, 06 Jun 2017 14:59:52 GMT

I checked the runtime of this function in the SPIS example in SDK 13 and measured ~7us. If you follow all functions call from this function, it's has a lot of context switching. What do you expect the runtime to be?

RE: SPIS DMA Setup Slow

Christopher — Fri, 02 Jun 2017 21:18:26 GMT

The SpiDma() call simple checks for the spi_state to equal SPI_IDLE, and then calls the nrf_drv_spis_buffers_set().

RE: SPIS DMA Setup Slow

Daniel Wang — Wed, 03 May 2017 21:03:56 GMT

Could you show some code snippets on how you use nrf_drv_spis_buffers_set? what sdk version are you using?