RE: Confusion about double buffered pointer on UARTE

Susheel Nuguru — Thu, 29 Apr 2021 11:32:27 GMT

Glad that you have this figured out.

[quote user="Pete W"]Is there any value in using p_event->data.rxtx.bytes to get the number of bytes waiting, or can I assume that it will always be the number requested, i.e. RX_BUFFER_SIZE[/quote]

RX:BUFFER:SIZE not the same as rxtx.bytes.

RX_BUFFER_SIZE should be larger than the biggest single RX transaction your application does..

RE: Confusion about double buffered pointer on UARTE

Pete W — Tue, 27 Apr 2021 14:50:43 GMT

I think I have a grip of this now. I had a bug in my main byte handler function which wasn't helping matters, and was the reason I was trying to use two 1-byte buffers. I now have two rx_buffers, each 10 bytes long, which gives me plenty of margin. I initialise the pointers in the initialisation using:

nrfx_uarte_rx(&uarte0, rx_buffer[0], RX_BUFFER_SIZE);
nrfx_uarte_rx(&uarte0, rx_buffer[1], RX_BUFFER_SIZE);

and then in my event handler I have:

case NRFX_UARTE_EVT_RX_DONE:

p_data = p_event->data.rxtx.p_data;

num_bytes = RX_BUFFER_SIZE;

while(num_bytes--)
{

my_rx_byte_handler(*(p_data++)); // call the external handler to dump the latest bytes into large buffer
}

nrfx_uarte_rx(&uarte0, p_event->data.rxtx.p_data, RX_BUFFER_SIZE); // ensure primary and secondary buffers flip

break;

case NRFX_UARTE_EVT_ERROR:

nrfx_uarte_rx(&uarte0, rx_buffer[0], RX_BUFFER_SIZE);
nrfx_uarte_rx(&uarte0, rx_buffer[1], RX_BUFFER_SIZE);

break;

I added a check to see what p_data is doing and it toggles between the two rx buffers, as expected, confirming that the double buffering of the pointers is working.

Is there any value in using p_event->data.rxtx.bytes to get the number of bytes waiting, or can I assume that it will always be the number requested, i.e. RX_BUFFER_SIZE

Regards,

Pete