Dial Tone

UART Command Fails After Stall Debug

Symptom

A colleague's command handler answers every command until a sender stops partway through one. The next command, sent in full, gets ERR. The registers and bit fields are on the Datasheet tab.

Circuit

Block diagram: a host serial console sends bytes into U1's USART1 on PA10 and reads replies from PA9, with a TP1 serial analyzer probing the PA9 transmit net

Pass condition

Each command that ends in a newline gets its reply. An abandoned one gets none.

Expected transcript: PING arrives without a newline at 2 ms and draws no reply, the line stays quiet for 20 ms or more, then ECHO colon ready arrives at 24 ms and the only reply is ready

Notes

Senders on the host keep issuing commands for as long as the board runs, pausing under 5 ms inside one and 20 ms or more once they quit.

Related challenges

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