HardwareSerial::end(bool) review + Baud Rate detection review and example (espressif#8762)

* removes pin detaching from end(false) * adds UART0 baud rate detection example * fixes baud rate messages

Author: SuGlider

cores/esp32/HardwareSerial.cpp

@@ -183,7 +183,7 @@ _eventTask(NULL)
 
 HardwareSerial::~HardwareSerial()
 {
- end();
+ end(true); // explicit Full UART termination
 #if !CONFIG_DISABLE_HAL_LOCKS
  if(_lock != NULL){
  vSemaphoreDelete(_lock);
@@ -398,7 +398,7 @@ void HardwareSerial::begin(unsigned long baud, uint32_t config, int8_t rxPin, in
  if(_uart) {
  // in this case it is a begin() over a previous begin() - maybe to change baud rate
  // thus do not disable debug output
- end(false);
+ end(false); // disables IDF UART driver and UART event Task + sets _uart to NULL
  }
 
  // IDF UART driver keeps Pin setting on restarting. Negative Pin number will keep it unmodified.
@@ -413,7 +413,7 @@ void HardwareSerial::begin(unsigned long baud, uint32_t config, int8_t rxPin, in
  yield();
  }
 
- end(false);
+ end(false); // disables IDF UART driver and UART event Task + sets _uart to NULL
 
  if(detectedBaudRate) {
  delay(100); // Give some time...
@@ -470,10 +470,8 @@ void HardwareSerial::end(bool fullyTerminate)
  // do not invalidate callbacks, detach pins, invalidate DBG output
  uart_driver_delete(_uart_nr);
  }
-
- uartEnd(_uart_nr);
- _uart = 0;
- _destroyEventTask();
+ _destroyEventTask(); // when IDF uart driver is deleted, _eventTask must finish too
+ _uart = NULL;
 }
 
 void HardwareSerial::setDebugOutput(bool en)

cores/esp32/esp32-hal-uart.c

@@ -884,32 +884,29 @@ void uartStartDetectBaudrate(uart_t *uart) {
  return;
  }
 
-#if CONFIG_IDF_TARGET_ESP32C3 || CONFIG_IDF_TARGET_ESP32C6 || CONFIG_IDF_TARGET_ESP32H2
+// Baud rate detection only works for ESP32 and ESP32S2
+#if CONFIG_IDF_TARGET_ESP32 || CONFIG_IDF_TARGET_ESP32S2
+ uart_dev_t *hw = UART_LL_GET_HW(uart->num);
+ hw->auto_baud.glitch_filt = 0x08;
+ hw->auto_baud.en = 0;
+ hw->auto_baud.en = 1;
+#else
 
  // ESP32-C3 requires further testing
  // Baud rate detection returns wrong values 
 
- log_e("ESP32-C3 baud rate detection is not supported.");
+ log_e("baud rate detection for this SoC is not supported.");
  return;
 
  // Code bellow for C3 kept for future recall
  //hw->rx_filt.glitch_filt = 0x08;
  //hw->rx_filt.glitch_filt_en = 1;
  //hw->conf0.autobaud_en = 0;
  //hw->conf0.autobaud_en = 1;
-#elif CONFIG_IDF_TARGET_ESP32S3
- log_e("ESP32-S3 baud rate detection is not supported.");
- return;
-#else
- uart_dev_t *hw = UART_LL_GET_HW(uart->num);
- hw->auto_baud.glitch_filt = 0x08;
- hw->auto_baud.en = 0;
- hw->auto_baud.en = 1;
 #endif
 }
 
-unsigned long
-uartDetectBaudrate(uart_t *uart)
+unsigned long uartDetectBaudrate(uart_t *uart)
 {
  if(uart == NULL) {
  return 0;
@@ -955,11 +952,7 @@ uartDetectBaudrate(uart_t *uart)
 
  return default_rates[i];
 #else
-#if CONFIG_IDF_TARGET_ESP32C3 || CONFIG_IDF_TARGET_ESP32C6 || CONFIG_IDF_TARGET_ESP32H2
- log_e("ESP32-C3 baud rate detection is not supported.");
-#else
- log_e("ESP32-S3 baud rate detection is not supported.");
-#endif
+ log_e("baud rate detection this SoC is not supported.");
  return 0;
 #endif
 }

libraries/ESP32/examples/Serial/BaudRateDetect_Demo/BaudRateDetect_Demo.ino

@@ -0,0 +1,37 @@
+/*
+ This Sketch demonstrates how to detect and set the baud rate when the UART0 is connected to
+ some port that is sending data. It can be used with the Arduino IDE Serial Monitor to send the data.
+
+ Serial.begin(0) will start the baud rate detection. Valid range is 300 to 230400 baud.
+ It will try to detect for 20 seconds, by default, while reading RX.
+ This timeout of 20 seconds can be changed in the begin() function through <<timeout_ms>> parameter:
+ 
+ void HardwareSerial::begin(baud, config, rxPin, txPin, invert, <<timeout_ms>>, rxfifo_full_thrhd)
+
+ It is necessary that the other end sends some data within <<timeout_ms>>, otherwise the detection won't work.
+
+ IMPORTANT NOTE: baud rate detection seem to only work with ESP32 and ESP32-S2. 
+ In other other SoCs, it doesn't work.
+
+*/
+
+// Open the Serial Monitor with testing baud start typing and sending caracters
+void setup() {
+ Serial.begin(0); // it will try to detect the baud rate for 20 seconds
+ 
+ Serial.print("\n==>The baud rate is ");
+ Serial.println(Serial.baudRate()); 
+ 
+ //after 20 seconds timeout, when not detected, it will return zero - in this case, we set it back to 115200.
+ if (Serial.baudRate() == 0) {
+ // Trying to set Serial to a safe state at 115200
+ Serial.end();
+ Serial.begin(115200);
+ Serial.setDebugOutput(true);
+ delay(1000);
+ log_e("Baud rate detection failed.");
+ }
+ }
+
+void loop() {
+}