Add Serial UART break reporting (#1130)

Added SerialUART::getBreakReceived()

Author: Beirdo

cores/rp2040/SerialUART.cpp

@@ -200,6 +200,7 @@ void SerialUART::begin(unsigned long baud, uint16_t config) {
     } else {
         // Polling mode has no IRQs used
     }
+    _break = false;
     _running = true;
 }
 
@@ -365,6 +366,25 @@ SerialUART::operator bool() {
     return _running;
 }
 
+bool SerialUART::getBreakReceived() {
+    if (!_running) {
+        return false;
+    }
+
+    if (_polling) {
+        _handleIRQ(false);
+    } else {
+        _pumpFIFO();
+    }
+
+    mutex_enter_blocking(&_fifoMutex);
+    bool break_received = _break;
+    _break = false;
+    mutex_exit(&_fifoMutex);
+
+    return break_received;
+}
+
 void arduino::serialEvent1Run(void) {
     if (serialEvent1 && Serial1.available()) {
         serialEvent1();
@@ -391,8 +411,12 @@ void __not_in_flash_func(SerialUART::_handleIRQ)(bool inIRQ) {
     uart_get_hw(_uart)->icr = UART_UARTICR_RTIC_BITS | UART_UARTICR_RXIC_BITS;
     while (uart_is_readable(_uart)) {
         uint32_t raw = uart_get_hw(_uart)->dr;
-        if (raw & 0x700) {
-            // Framing, Parity, or Break.  Ignore this bad char
+        if (raw & 0x400) {
+            // break!
+            _break = true;
+            continue;
+        } else if (raw & 0x300) {
+            // Framing, Parity Error.  Ignore this bad char
             continue;
         }
         uint8_t val = raw & 0xff;

cores/rp2040/SerialUART.h

@@ -71,6 +71,10 @@ class SerialUART : public HardwareSerial {
     // Not to be called by users, only from the IRQ handler.  In public so that the C-language IQR callback can access it
     void _handleIRQ(bool inIRQ = true);
 
+    // Allows the user to sleep until a break is received (self-clears the flag
+    // on read)
+    bool getBreakReceived();
+
 private:
     bool _running = false;
     uart_inst_t *_uart;
@@ -81,6 +85,7 @@ class SerialUART : public HardwareSerial {
     mutex_t _mutex;
     bool _polling = false;
     bool _overflow;
+    bool _break;
 
     // Lockless, IRQ-handled circular queue
     uint32_t _writer;