Max uart DMA limit

[haricane]

Hello Nordic Semi team, 

I am using the nrf52832 to send and recv data to a wifi module via uart. 

I am using the dma feature on the uart, and things work fine when RXD.MAXCNT < = 255. When RXD.MAXCNT > 255, there is a data loss on rx.  

void uart_recv_start(const void *buff_ptr, uint16_t size)
{
NRF_UARTE0->RXD.MAXCNT = size;
NRF_UARTE0->RXD.PTR = (uint32_t)buff_ptr;
NRF_UARTE0->TASKS_STARTRX = 1;
return ;
}

Is there a 255 byte limit on the RXD.MAXCNT? 

Kind regards, 

Hari 

[Vidar Berg]

Hello Hari,

Yes, your observation is correct, unfortunately. On nRF52832, you are limited to 256 bytes. This can be seen from the number of bits available in the .MAXCNT register.

 

Kind regards,

Vidar

[haricane]

thanks for the detailed info Vidar. I guess the info was there in the datasheet :)