fixes UART pin detach on end() (#7402)

Author: SuGlider

cores/esp32/HardwareSerial.cpp

@@ -145,6 +145,10 @@ _eventTask(NULL)
 #if !CONFIG_DISABLE_HAL_LOCKS
     ,_lock(NULL)
 #endif
+,_rxPin(-1) 
+,_txPin(-1)
+,_ctsPin(-1)
+,_rtsPin(-1)
 {
 #if !CONFIG_DISABLE_HAL_LOCKS
     if(_lock == NULL){
@@ -384,7 +388,8 @@ void HardwareSerial::begin(unsigned long baud, uint32_t config, int8_t rxPin, in
 
     // Set UART RX timeout
     uartSetRxTimeout(_uart, _rxTimeout);
-
+    _rxPin = rxPin;
+    _txPin = txPin;
     HSERIAL_MUTEX_UNLOCK();
 }
 
@@ -403,6 +408,8 @@ void HardwareSerial::end(bool fullyTerminate)
         if (uartGetDebug() == _uart_nr) {
             uartSetDebug(0);
         }
+        uartDetachPins(_uart, _rxPin, _txPin, _ctsPin, _rtsPin);
+        _rxPin = _txPin = _ctsPin = _rtsPin = -1;
     }
     delay(10);
     uartEnd(_uart);
@@ -507,10 +514,19 @@ void HardwareSerial::setRxInvert(bool invert)
 void HardwareSerial::setPins(int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin)
 {
     if(_uart == NULL) {
-        log_e("setPins() shall be called after begin() - nothing done");
+        log_e("setPins() shall be called after begin() - nothing done\n");
         return;
     }
-    uartSetPins(_uart, rxPin, txPin, ctsPin, rtsPin);
+
+    // uartSetPins() checks if pins are valid for each function and for the SoC 
+    if (uartSetPins(_uart, rxPin, txPin, ctsPin, rtsPin)) {
+        _txPin = _txPin >= 0 ? txPin : _txPin;
+        _rxPin = _rxPin >= 0 ? rxPin : _rxPin;
+        _rtsPin = _rtsPin >= 0 ? rtsPin : _rtsPin;
+        _ctsPin = _ctsPin >= 0 ? ctsPin : _ctsPin;
+    } else {
+        log_e("Error when setting Serial port Pins. Invalid Pin.\n");
+    }
 }
 
 // Enables or disables Hardware Flow Control using RTS and/or CTS pins (must use setAllPins() before)

cores/esp32/HardwareSerial.h

@@ -176,6 +176,7 @@ class HardwareSerial: public Stream
 #if !CONFIG_DISABLE_HAL_LOCKS
     SemaphoreHandle_t _lock;
 #endif
+    int8_t _rxPin, _txPin, _ctsPin, _rtsPin;
 
     void _createEventTask(void *args);
     void _destroyEventTask(void);

cores/esp32/esp32-hal-uart.c

@@ -23,6 +23,9 @@
 #include "soc/soc_caps.h"
 #include "soc/uart_struct.h"
 
+#include "hal/gpio_hal.h"
+#include "esp_rom_gpio.h"
+
 static int s_uart_debug_nr = 0;
 
 struct uart_struct_t {
@@ -69,6 +72,40 @@ static uart_t _uart_bus_array[] = {
 
 #endif
 
+// IDF UART has no detach function. As consequence, after ending a UART, the previous pins continue
+// to work as RX/TX. It can be verified by changing the UART pins and writing to the UART. Output can 
+// be seen in the previous pins and new pins as well. 
+// Valid pin UART_PIN_NO_CHANGE is defined to (-1)
+// Negative Pin Number will keep it unmodified, thus this function can detach individual pins
+void uartDetachPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin)
+{
+    if(uart == NULL) {
+        return;
+    }
+
+    UART_MUTEX_LOCK();
+    if (txPin >= 0) {
+        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[txPin], PIN_FUNC_GPIO);
+        esp_rom_gpio_connect_out_signal(txPin, SIG_GPIO_OUT_IDX, false, false);
+    }
+
+    if (rxPin >= 0) {
+        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[rxPin], PIN_FUNC_GPIO);
+        esp_rom_gpio_connect_in_signal(GPIO_FUNC_IN_LOW, UART_PERIPH_SIGNAL(uart->num, SOC_UART_RX_PIN_IDX), false);
+    }
+
+    if (rtsPin >= 0) {
+        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[rtsPin], PIN_FUNC_GPIO);
+        esp_rom_gpio_connect_out_signal(rtsPin, SIG_GPIO_OUT_IDX, false, false);
+    }
+
+    if (ctsPin >= 0) {
+        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[ctsPin], PIN_FUNC_GPIO);
+        esp_rom_gpio_connect_in_signal(GPIO_FUNC_IN_LOW, UART_PERIPH_SIGNAL(uart->num, SOC_UART_CTS_PIN_IDX), false);
+    }
+    UART_MUTEX_UNLOCK();  
+}
+
 // solves issue https://github.com/espressif/arduino-esp32/issues/6032
 // baudrate must be multiplied when CPU Frequency is lower than APB 80MHz
 uint32_t _get_effective_baudrate(uint32_t baudrate) 
@@ -108,15 +145,16 @@ bool uartIsDriverInstalled(uart_t* uart)
 
 // Valid pin UART_PIN_NO_CHANGE is defined to (-1)
 // Negative Pin Number will keep it unmodified, thus this function can set individual pins
-void uartSetPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin)
+bool uartSetPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin)
 {
     if(uart == NULL) {
-        return;
+        return false;
     }
     UART_MUTEX_LOCK();
     // IDF uart_set_pin() will issue necessary Error Message and take care of all GPIO Number validation.
-    uart_set_pin(uart->num, txPin, rxPin, rtsPin, ctsPin); 
+    bool retCode = uart_set_pin(uart->num, txPin, rxPin, rtsPin, ctsPin) == ESP_OK; 
     UART_MUTEX_UNLOCK();  
+    return retCode;
 }
 
 // 

cores/esp32/esp32-hal-uart.h

@@ -91,8 +91,9 @@ int uartGetDebug();
 
 bool uartIsDriverInstalled(uart_t* uart);
 
-// Negative Pin Number will keep it unmodified, thus this function can set individual pins
-void uartSetPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin);
+// Negative Pin Number will keep it unmodified, thus this function can set/reset individual pins
+bool uartSetPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin);
+void uartDetachPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin);
 
 // Enables or disables HW Flow Control function -- needs also to set CTS and/or RTS pins
 void uartSetHwFlowCtrlMode(uart_t *uart, uint8_t mode, uint8_t threshold);