UARTE STOPRX on exact byte

[parco]

Hi there,

I'm issuing a STOPRX at a specific time but I'm noticing that more bytes are being put into the buffer from after the STOPRX was issued.

Is there a way to stop the UARTE on the exact byte and process, and receive all bytes from that point on to a different buffer?

Please advise.

UPDATE

After triggering a STOPRX, the UARTE will hang around for a few more bytes, placing them in the same buffer and then calling ENDRX. This is problematic since these new bytes are part of a different message.

Here you can see that STOPRX is triggered during some small idle times, yet the ENDRX doesn't happen till much later.

This results in ENDRX being called with 11, 6 and 1 bytes read (when it should be 6, 6 and 6 bytes read)

[RK]

No. The documentation addresses this. if you're using nRF52 (UARTE so I assume so) up to 4 bytes can be received after the STOPRX task. How many actually are depends on what's on the other end transmitting data to you, if it's slow stopping after the RTS signal is deactivated and keeps sending more data, the UARTE is going to receive it. I assume you're using hardware flow control.

Those bytes however go into the RX FIFO so you can update the memory buffer pointer after you get the ENDRX event and then flush to start those bytes off in your new buffer.

[RK]

No it's not possible to fake something to force ENDRX to fire early, even with flow control, if the other end was slow stopping sending, the UARTE will continue to receive up to 4 characters in order to ensure it doesn't lose data, well unless the other end kept on sending yet more data.

I do agree there is some ambiguity here which the docs don't cover. The UART is going to continue to receive bytes, but it's quite reasonable to assume it would ENDTX, buffer anything coming in in the TX buffer and write it out when the next EasyDMA starts. However it seems it doesn't do that. But it would be good to have clarification.

I still don't see why this is a problem however. You call STOP, you wait for END, you look at see how many characters you have in your buffer, you wanted 4, you have 7. You copy 3 into the new buffer and set the EasyDMA pointer to point to the next byte and restart.