NRF52840 SPI transfer buffer length

[scao]

Hi,

Im using NRF52840 with SDK 14.2. Currently trying to use SPI to read a large amount of data. Currently, the SDK is limiting the array buffer size to 255. My understanding is that for NRF52832, the max TXD.MAXCNT are limited to 255 because of easyDMA.

Looking at the datasheet for NRF52840, this register seemed to have changed to 16 bits instead. Does this mean I could safely increase the size of my transfer buffer, through changing the SDK, to have SPI drivers transfer more than 255 bytes without problem?

If that is the case, then I do not think SDK should have this limitation, and it would be good to have this corrected.

Regards

Sheng

[Jakub Rzeszutko]

Hi,

Yes you can increase the size of your transfer buffer, we will update it in comming SDK15.

[alasknnj]

Jakub Rzeszutko is it possible to send more than 255 bytes now? The SPI transfer function still only accepts uint8_t. If I change that to uint16_t, should it work? I observed that all other transfer functions, which use the nrfx_spim_xfer_desc_t, use size_t instead.

I also found here that the engineering A has can't be set with 16 bit for the TXD.MAXCNT register, is that really true? DOes that work for Rev 1?

[Jakub Rzeszutko]

Hi,

Transfers longer than 255 bytes can be realized using nrfx functions. It is not implemented in legacy driver. I expect that changing buffer length in legacy driver may not be enough.

For sure the newest revision of nrf52840 will have buffers 16 bytes long.

[AlexW]

Hi,

I am using SDK 15.3 and function  nrf_drv_spi_transfer and the SPI buffer length are still limited to 255 (unit8_t).
Unfortunately changing the type to uint16_t in the function definition does not work. SPI transmissions larger that 255 byte still won't work.

Can you suggest what I have to change to get it work?

I am using nrf52840 and nrf52832.

Thanks, Alex