Adjust SerialPIO flush timeouts

earlephilhower · earlephilhower · commit 1cfc9514d4c5 · 2025-12-07T08:52:10.000-08:00
Fixes #3256 Reduce the minimum timeout for SerialPIO::flush from 1ms to 1us.
diff --git a/cores/rp2040/SerialPIO.cpp b/cores/rp2040/SerialPIO.cpp
@@ -355,10 +355,10 @@ void SerialPIO::flush() {
         return;
     }
     while (!pio_sm_is_tx_fifo_empty(_txPIO, _txSM)) {
-        delay(1); // Wait for all FIFO to be read
+        /* noop */ // Busy wait for all FIFO to be read
     }
     // Could have 1 byte being transmitted, so wait for bit times
-    delay((1000 * (_txBits + 1)) / _baud);
+    delayMicroseconds((1000000 * (_txBits + 3 /* start + stop + parity */)) / _baud);
 }
 
 size_t SerialPIO::write(uint8_t c) {

Original file line number	Diff line number	Diff line change
`@@ -355,10 +355,10 @@ void SerialPIO::flush() {`
`355`	`355`	`return;`
`356`	`356`	`}`
`357`	`357`	`while (!pio_sm_is_tx_fifo_empty(_txPIO, _txSM)) {`
`358`		`- delay(1); // Wait for all FIFO to be read`
	`358`	`+ /* noop */ // Busy wait for all FIFO to be read`
`359`	`359`	`}`
`360`	`360`	`// Could have 1 byte being transmitted, so wait for bit times`
`361`		`- delay((1000 * (_txBits + 1)) / _baud);`
	`361`	`+ delayMicroseconds((1000000 * (_txBits + 3 /* start + stop + parity */)) / _baud);`
`362`	`362`	`}`
`363`	`363`
`364`	`364`	`size_t SerialPIO::write(uint8_t c) {`