Fix SerialPIO::available during wraparound (#3143)

earlephilhower · web-flow · commit d0c8bbec3151 · 2025-09-20T11:15:03.000-07:00
Fixes #3142
diff --git a/cores/rp2040/SerialPIO.cpp b/cores/rp2040/SerialPIO.cpp
@@ -338,7 +338,7 @@ int SerialPIO::available() {
     if (!_running || !m || (_rx == NOPIN)) {
         return 0;
     }
-    return (_writer - _reader) % _fifoSize;
+    return (_fifoSize + _writer - _reader) % _fifoSize;
 }
 
 int SerialPIO::availableForWrite() {

Original file line number	Diff line number	Diff line change
`@@ -338,7 +338,7 @@ int SerialPIO::available() {`
`338`	`338`	`if (!_running \|\| !m \|\| (_rx == NOPIN)) {`
`339`	`339`	`return 0;`
`340`	`340`	`}`
`341`		`- return (_writer - _reader) % _fifoSize;`
	`341`	`+ return (_fifoSize + _writer - _reader) % _fifoSize;`
`342`	`342`	`}`
`343`	`343`
`344`	`344`	`int SerialPIO::availableForWrite() {`