SPI DMA transfer Fails for large buffer

[Thangaraj]

HI All, We are using NRF52, S132 Softdevice , SDK 11.0.0.

In SPI DMA transfer, when we try to increase size of the m_tx_data greater than 254 bytes, it failed. It is working when the size is less than or equal to 254 bytes.

Cant we send more than 254 bytes using SPI DMA at a time? Why this is failing?

Thanks,

[RK]

No you can't - the size is a uint8, so limited to 255

[Thangaraj]

Is that possible if we change it to uint32?

[RK]

No of course you can't, well you can change it to uint32_t if you like but since the DMA register is 8 bits wide, 255 bytes is the maximum transfer you can do with DMA so it's not going to help you. The register definition etc is all in the product spec. DMA size register is 8bit for all the nRF52 peripherals.

[Thangaraj]

Thanks for ur support RK