Merge pull request #15240 from OpenNuvoton/nuvoton_esp8266_flow_control_reconnect

ESP8266: Fix serial flow control inconsistency on reconnect

Author: 0xc0170

connectivity/drivers/wifi/esp8266-driver/ESP8266/ESP8266.cpp

@@ -193,7 +193,7 @@ struct ESP8266::fw_at_version ESP8266::at_version()
     return _at_v;
 }
 
-bool ESP8266::stop_uart_hw_flow_ctrl(void)
+bool ESP8266::stop_uart_hw_flow_ctrl(bool board_only)
 {
     bool done = true;
 #if DEVICE_SERIAL_FC
@@ -202,9 +202,11 @@ bool ESP8266::stop_uart_hw_flow_ctrl(void)
         // Stop board's flow control
         _serial.set_flow_control(SerialBase::Disabled, _serial_rts, _serial_cts);
 
-        // Stop ESP8266's flow control
-        done = _parser.send("AT+UART_CUR=%u,8,1,0,0", MBED_CONF_ESP8266_SERIAL_BAUDRATE)
-               && _parser.recv("OK\n");
+        if (!board_only) {
+            // Stop ESP8266's flow control
+            done = _parser.send("AT+UART_CUR=%u,8,1,0,0", MBED_CONF_ESP8266_SERIAL_BAUDRATE)
+                   && _parser.recv("OK\n");
+        }
     }
 
 #endif

connectivity/drivers/wifi/esp8266-driver/ESP8266/ESP8266.h

@@ -455,9 +455,10 @@ class ESP8266 {
     /**
      * Stop board's and ESP8266's UART flow control
      *
+     * @param board_only    true to apply to board only, false to apply both
      * @return true if started
      */
-    bool stop_uart_hw_flow_ctrl();
+    bool stop_uart_hw_flow_ctrl(bool board_only = false);
 
     /*
      * From AT firmware v1.7.0.0 onwards enables TCP passive mode

connectivity/drivers/wifi/esp8266-driver/ESP8266Interface.cpp

@@ -722,8 +722,14 @@ bool ESP8266Interface::_get_firmware_ok()
 nsapi_error_t ESP8266Interface::_init(void)
 {
     if (!_initialized) {
-        _pwr_pin.power_off();
-        _pwr_pin.power_on();
+        if (_pwr_pin.is_connected()) {
+            _pwr_pin.power_off();
+            _pwr_pin.power_on();
+            /* Align board's serial flow control with ESP8266's, resetting to disabled on re-power or reset */
+            if (!_esp.stop_uart_hw_flow_ctrl(true)) {
+                return NSAPI_ERROR_DEVICE_ERROR;
+            }
+        }
 
         if (_reset() != NSAPI_ERROR_OK) {
             return NSAPI_ERROR_DEVICE_ERROR;
@@ -780,6 +786,10 @@ nsapi_error_t ESP8266Interface::_reset()
         ThisThread::sleep_for(delay);
         _esp.flush();
         _rst_pin.rst_deassert();
+        /* Align board's serial flow control with ESP8266's, resetting to disabled on re-power or reset */
+        if (!_esp.stop_uart_hw_flow_ctrl(true)) {
+            return NSAPI_ERROR_DEVICE_ERROR;
+        }
     } else {
         _esp.flush();
         if (!_esp.at_available()) {