nrfx_uarte_rx doesn't receive/return last byte

[bearsh]

I need to implement a simple uart protocol. most messages are fixed length (8bytes) with some exceptions.

here what I do in pseudo code, I send 8bytes and expect 8bytes back.

1. nrfx_uarte_tx() [8bytes]
2. in evt handler, TX_DONE event, nrfx_uarte_rx() [8bytes]
3. RX_DONE event never happens

if I change nrfx_uarte_rx() to receive 7bytes, the first 7bytes of the message is received correctly.

to receive variable size messages, my idea is to receive as many bytes as I need to get the length information, then issue another nrfx_uarte_rx() call to get the rest.

the problem now is, why do I not receive the last byte of my message?

Chip: nrf52840 (ublox NINA-B3)
SDK: 15.2.0
OS: Linux
Toolchain: GNU Tools for Arm Embedded Processors 7-2018-q3-update

[Jørgen Holmefjord]

Have you checked with a logic analyzer that you actually receive 8 bytes on the RX line? Is there any specific reason that you wait for the TX_DONE event before calling RX function? You can call the RX function simultaneously with TX to set the buffer and start the receive operation, then the buffer will be filled when bytes are coming in.

[bearsh]

sorry, in the end it was something different which led me to the wrong conclusion above.

thanks for your hint regarding the receive operation.