fix(uart): Sets XTAL as clock source for uart

cores/esp32/HardwareSerial.cpp

@@ -96,7 +96,7 @@ void serialEventRun(void) {
 #endif
 
 HardwareSerial::HardwareSerial(uint8_t uart_nr)
-  : _uart_nr(uart_nr), _uart(NULL), _rxBufferSize(256), _txBufferSize(0), _onReceiveCB(NULL), _onReceiveErrorCB(NULL), _onReceiveTimeout(false), _rxTimeout(2),
+  : _uart_nr(uart_nr), _uart(NULL), _rxBufferSize(256), _txBufferSize(0), _onReceiveCB(NULL), _onReceiveErrorCB(NULL), _onReceiveTimeout(false), _rxTimeout(1),
     _rxFIFOFull(0), _eventTask(NULL)
 #if !CONFIG_DISABLE_HAL_LOCKS
     ,

cores/esp32/esp32-hal-uart.c

@@ -503,9 +503,21 @@ uart_t *uartBegin(
   uart_config.flow_ctrl = UART_HW_FLOWCTRL_DISABLE;
   uart_config.rx_flow_ctrl_thresh = rxfifo_full_thrhd;
   uart_config.baud_rate = baudrate;
-  // CLK_APB for ESP32|S2|S3|C3 -- CLK_PLL_F40M for C2 -- CLK_PLL_F48M for H2 -- CLK_PLL_F80M for C6
-  uart_config.source_clk = UART_SCLK_DEFAULT;
-
+  // there is an issue when returning from light sleep with the C6 and H2: the uart baud rate is not restored
+  // therefore, uart clock source will set to XTAL for all SoC that support it. This fix solves the C6|H2 issue.
+#if SOC_UART_SUPPORT_XTAL_CLK
+  uart_config.source_clk = UART_SCLK_XTAL; // valid for C2, S3, C3, C6, H2 and P4
+#elif SOC_UART_SUPPORT_REF_TICK
+  if (baudrate <= 1000000) {
+    uart_config.source_clk = UART_SCLK_REF_TICK; // valid for ESP32, S2 - MAX supported baud rate is 1MHz
+  } else {
+    uart_config.source_clk = UART_SCLK_APB; // baudrate may change with the APB Frequency!
+  }
+#else
+  // Default CLK Source: CLK_APB for ESP32|S2|S3|C3 -- CLK_PLL_F40M for C2 -- CLK_PLL_F48M for H2 -- CLK_PLL_F80M for C6
+  uart_config.source_clk = UART_SCLK_DEFAULT; // baudrate may change with the APB Frequency!
+#endif
+
   UART_MUTEX_LOCK();
   bool retCode = ESP_OK == uart_driver_install(uart_nr, rx_buffer_size, tx_buffer_size, 20, &(uart->uart_event_queue), 0);
 
@@ -778,25 +790,25 @@ void uartSetBaudRate(uart_t *uart, uint32_t baud_rate) {
     return;
   }
   UART_MUTEX_LOCK();
-  uint32_t sclk_freq;
-  if (uart_get_sclk_freq(UART_SCLK_DEFAULT, &sclk_freq) == ESP_OK) {
-    uart_ll_set_baudrate(UART_LL_GET_HW(uart->num), baud_rate, sclk_freq);
+  if (uart_set_baudrate(uart->num, baud_rate) == ESP_OK) {
+    uart->_baudrate = baud_rate;
+  } else {
+    log_e("Setting UART%d baud rate to %d has failed.", uart->num, baud_rate);
   }
-  uart->_baudrate = baud_rate;
   UART_MUTEX_UNLOCK();
 }
 
 uint32_t uartGetBaudRate(uart_t *uart) {
   uint32_t baud_rate = 0;
-  uint32_t sclk_freq;
 
   if (uart == NULL) {
     return 0;
   }
 
   UART_MUTEX_LOCK();
-  if (uart_get_sclk_freq(UART_SCLK_DEFAULT, &sclk_freq) == ESP_OK) {
-    baud_rate = uart_ll_get_baudrate(UART_LL_GET_HW(uart->num), sclk_freq);
+  if (uart_get_baudrate(uart->num, &baud_rate) != ESP_OK) {
+    log_e("Getting UART%d baud rate has failed.", uart->num);
+    baud_rate = (uint32_t) -1; // return value when failed
   }
   UART_MUTEX_UNLOCK();
   return baud_rate;