nRF52840 SPIM Easy DMA buffer >255bytes

[tealtech]

We are using the nRF52840 SPIM0 to read 2048 bytes from an SPI slave. ( SES / SDK15.3 )

The nrf libraries only seem to support  a maximum of 255 bytes, so we have compiler warnings when trying to us a uint16_t value as the buffer size.

Reading through the Q&A's it seems that the nRF52840 is capable of this, and the libraries were being updated to support it.

Have the libraries been updated?  Is there an example of an SPIM transfer > 255 bytes using these new libraries?

[Einar Thorsrud]

Hi,

The driver nrf_drv* use uint8_t for the length field for historic reasons (nRF52832). As @turboj wrote, this limitation is not present in nrfx, so you can work around this by using the nrfx_spim driver directly.

[tealtech]

I've started out with the SPI library example, which still utilizes the old nrf libraries.  Are there any newer examples which use only the nrfx spim drivers?

[Einar Thorsrud]

There are no examples that use nrfx directly. You can do it, but then you should remember to remove all configurations for the legacy driver in your projects sdk_config.h. Another alternative, which may be easier, is to just modify the nrf_drv_spi.c/.h files to use size_t. As you can see from the nrf_drv_spi implementation it essentially just calls the nrfx drivers, so changing all the length parameters from uint8_t to size_t should be enough.

[tealtech]

Thanks Einar.  I removed the legacy drivers and libraries and updated the calls and it all works perfectly.