feat(uart): Add function to invert hardware UART Tx line (#11428)

* feat(uart): Add function to invert hardware UART Tx line

Simply clone existing Rx functionality for Tx.
Allow granular control over both lines.
Avoid overloading HardwareSerial::begin() to change the bool invert parameter to a bitmask type.
Add an untested implementation for ESP32C6, ESP32H2, ESP32P4 that references the different register
naming on those chips.

* feat(uart): Refactor UART signal inversion handling

Refactor UART inversion functions to use a helper for signal inversion. Update UART bus array structure to include inversion mask.

* feat(uart): Add UART signal inversion functions

Added functions for UART signal inversion and updated existing function signatures.

* feat(uart): Refactor UART signal inversion handling

* feat(uart): Change setRxInvert and setTxInvert to return bool

* feat(uart) : Refactor serial inversion methods to return bool

Changed setRxInvert, setTxInvert to return bool. Added setCtsInvert and setRtsInvert methods.

* feat(uart): adds commentatries

Added functions for UART pins signal inversion.

* feat(uart): add commentaties

* feat(uart): Refactor uartPinSignalInversion for mutex locking

* Refactor UART inversion functions to use new method

* fix(uart): missing uart struct usage

* fix(uart): missing function return value

* feat(uart): add commentaties

* fix(uart): inverting rx instead of tx

* feat(uart): logging for UART signal inversion

Added logging for signal inversion in UART functions.

* feat(uart): standard verbose log message

* feat(uart): add not inverted verbose log message

* fix(uart): misspeling comment

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(uart): fixes bad code formating

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(uart): fixes misspeling

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(uart): fixes bad code formating

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(uart): fixes bad code formating

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(uart): fixes bad code formating

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(uart): fixes extra spaces

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(uart): extra spacing

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* feat(uart): Improve logging for UART signal inversion

* ci(pre-commit): Apply automatic fixes

---------

Co-authored-by: Sugar Glider <rodrigo.garcia@espressif.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

Author: 4 people

cores/esp32/HardwareSerial.cpp

@@ -572,8 +572,20 @@ HardwareSerial::operator bool() const {
   return uartIsDriverInstalled(_uart);
 }
 
-void HardwareSerial::setRxInvert(bool invert) {
-  uartSetRxInvert(_uart, invert);
+bool HardwareSerial::setRxInvert(bool invert) {
+  return uartSetRxInvert(_uart, invert);
+}
+
+bool HardwareSerial::setTxInvert(bool invert) {
+  return uartSetTxInvert(_uart, invert);
+}
+
+bool HardwareSerial::setCtsInvert(bool invert) {
+  return uartSetCtsInvert(_uart, invert);
+}
+
+bool HardwareSerial::setRtsInvert(bool invert) {
+  return uartSetRtsInvert(_uart, invert);
 }
 
 // negative Pin value will keep it unmodified

cores/esp32/HardwareSerial.h

@@ -356,7 +356,12 @@ class HardwareSerial : public Stream {
 
   void setDebugOutput(bool);
 
-  void setRxInvert(bool);
+  // functions used to enable or disable UART pins signal inversion
+  // returns the requested operation success status
+  bool setRxInvert(bool);
+  bool setTxInvert(bool);
+  bool setCtsInvert(bool);
+  bool setRtsInvert(bool);
 
   // Negative Pin Number will keep it unmodified, thus this function can set individual pins
   // setPins() can be called after or before begin()

cores/esp32/esp32-hal-uart.c

@@ -60,6 +60,7 @@ struct uart_struct_t {
   bool _inverted;                             // UART inverted signal
   uint8_t _rxfifo_full_thrhd;                 // UART RX FIFO full threshold
   int8_t _uart_clock_source;                  // UART Clock Source that should be used if user defines an specific one with setClockSource()
+  uint32_t inv_mask;                          // UART inverse mask used to maintain related pin state
 };
 
 #if CONFIG_DISABLE_HAL_LOCKS
@@ -68,21 +69,21 @@ struct uart_struct_t {
 #define UART_MUTEX_UNLOCK()
 
 static uart_t _uart_bus_array[] = {
-  {0, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {0, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #if SOC_UART_NUM > 1
-  {1, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {1, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 2
-  {2, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {2, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 3
-  {3, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {3, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 4
-  {4, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {4, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 5
-  {5, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {5, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 };
 
@@ -97,21 +98,21 @@ static uart_t _uart_bus_array[] = {
   xSemaphoreGive(uart->lock)
 
 static uart_t _uart_bus_array[] = {
-  {NULL, 0, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {NULL, 0, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #if SOC_UART_NUM > 1
-  {NULL, 1, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {NULL, 1, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 2
-  {NULL, 2, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {NULL, 2, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 3
-  {NULL, 3, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {NULL, 3, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 4
-  {NULL, 4, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {NULL, 4, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 #if SOC_UART_NUM > 5
-  {NULL, 5, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1},
+  {NULL, 5, false, 0, NULL, -1, -1, -1, -1, 0, 0, 0, 0, false, 0, -1, 0},
 #endif
 };
 
@@ -873,10 +874,20 @@ uart_t *uartBegin(
   if (retCode) {
     if (inverted) {
       // invert signal for both Rx and Tx
-      retCode &= ESP_OK == uart_set_line_inverse(uart_nr, UART_SIGNAL_TXD_INV | UART_SIGNAL_RXD_INV);
+      uint32_t _inv_mask = uart->inv_mask;
+      _inv_mask |= UART_SIGNAL_TXD_INV | UART_SIGNAL_RXD_INV;
+      retCode &= ESP_OK == uart_set_line_inverse(uart_nr, _inv_mask);
+      if (retCode) {
+        uart->inv_mask = _inv_mask;
+        log_v("UART%d: RX and TX signals are set to be inverted.", uart_nr);
+      }
     } else {
       // disable invert signal for both Rx and Tx
       retCode &= ESP_OK == uart_set_line_inverse(uart_nr, UART_SIGNAL_INV_DISABLE);
+      if (retCode) {
+        uart->inv_mask = UART_SIGNAL_INV_DISABLE;
+        log_v("UART%d: RX and TX signals are set not inverted.", uart_nr);
+      }
     }
   }
   // if all fine, set internal parameters
@@ -978,28 +989,58 @@ void uartEnd(uint8_t uart_num) {
   UART_MUTEX_UNLOCK();
 }
 
-void uartSetRxInvert(uart_t *uart, bool invert) {
+// Helper generic function that takes a uart_signal_inv_t mask to be properly applied to the designated uart pin
+// invMask can be UART_SIGNAL_RXD_INV, UART_SIGNAL_TXD_INV, UART_SIGNAL_RTS_INV, UART_SIGNAL_CTS_INV
+// returns the operation success status
+bool uartPinSignalInversion(uart_t *uart, uint32_t invMask, bool inverted) {
   if (uart == NULL) {
-    return;
+    return false;
   }
-#if CONFIG_IDF_TARGET_ESP32C6 || CONFIG_IDF_TARGET_ESP32H2 || CONFIG_IDF_TARGET_ESP32P4 || CONFIG_IDF_TARGET_ESP32C5
-  // POTENTIAL ISSUE :: original code only set/reset rxd_inv bit
-  // IDF or LL set/reset the whole inv_mask!
-  // if (invert)
-  //     ESP_ERROR_CHECK(uart_set_line_inverse(uart->num, UART_SIGNAL_RXD_INV));
-  // else
-  //     ESP_ERROR_CHECK(uart_set_line_inverse(uart->num, UART_SIGNAL_INV_DISABLE));
-  log_e("uartSetRxInvert is not supported in ESP32C6, ESP32H2 and ESP32P4");
-#else
-  // this implementation is better over IDF API because it only affects RXD
-  // this is supported in ESP32, ESP32-S2 and ESP32-C3
-  uart_dev_t *hw = UART_LL_GET_HW(uart->num);
-  if (invert) {
-    hw->conf0.rxd_inv = 1;
+  UART_MUTEX_LOCK();
+  uint32_t _inv_mask = uart->inv_mask;
+  if (inverted) {
+    _inv_mask |= invMask;
   } else {
-    hw->conf0.rxd_inv = 0;
+    _inv_mask &= ~invMask;
   }
-#endif
+  bool retCode = ESP_OK == uart_set_line_inverse(uart->num, _inv_mask);
+  if (retCode) {
+    uart->inv_mask = _inv_mask;
+  }
+  UART_MUTEX_UNLOCK();
+  return retCode;
+}
+
+bool uartSetRxInvert(uart_t *uart, bool invert) {
+  if (uartPinSignalInversion(uart, UART_SIGNAL_RXD_INV, invert)) {
+    log_v("UART%d: RX signal inversion %s", uart->num, invert ? "enabled" : "disabled");
+    return true;
+  }
+  return false;
+}
+
+bool uartSetTxInvert(uart_t *uart, bool invert) {
+  if (uartPinSignalInversion(uart, UART_SIGNAL_TXD_INV, invert)) {
+    log_v("UART%d: TX signal inversion %s", uart->num, invert ? "enabled" : "disabled");
+    return true;
+  }
+  return false;
+}
+
+bool uartSetCtsInvert(uart_t *uart, bool invert) {
+  if (uartPinSignalInversion(uart, UART_SIGNAL_CTS_INV, invert)) {
+    log_v("UART%d: CTS signal inversion %s", uart->num, invert ? "enabled" : "disabled");
+    return true;
+  }
+  return false;
+}
+
+bool uartSetRtsInvert(uart_t *uart, bool invert) {
+  if (uartPinSignalInversion(uart, UART_SIGNAL_RTS_INV, invert)) {
+    log_v("UART%d: RTS signal inversion %s", uart->num, invert ? "enabled" : "disabled");
+    return true;
+  }
+  return false;
 }
 
 uint32_t uartAvailable(uart_t *uart) {

cores/esp32/esp32-hal-uart.h

@@ -61,7 +61,15 @@ void uartFlushTxOnly(uart_t *uart, bool txOnly);
 bool uartSetBaudRate(uart_t *uart, uint32_t baud_rate);
 uint32_t uartGetBaudRate(uart_t *uart);
 
-void uartSetRxInvert(uart_t *uart, bool invert);
+// Helper generic function that takes a uart_signal_inv_t mask to be properly applied to the designated uart pin
+// invMask can be UART_SIGNAL_RXD_INV, UART_SIGNAL_TXD_INV, UART_SIGNAL_RTS_INV, UART_SIGNAL_CTS_INV
+// returns the operation success status
+bool uartPinSignalInversion(uart_t *uart, uint32_t invMask, bool inverted);
+// functions used to individually enable or disable UART pins inversion
+bool uartSetRxInvert(uart_t *uart, bool invert);
+bool uartSetTxInvert(uart_t *uart, bool invert);
+bool uartSetCtsInvert(uart_t *uart, bool invert);
+bool uartSetRtsInvert(uart_t *uart, bool invert);
 bool uartSetRxTimeout(uart_t *uart, uint8_t numSymbTimeout);
 bool uartSetRxFIFOFull(uart_t *uart, uint8_t numBytesFIFOFull);
 void uartSetFastReading(uart_t *uart);

tests/validation/uart/uart.ino

@@ -276,6 +276,10 @@ void enabled_uart_calls_test(void) {
   Serial1.setRxInvert(true);
   Serial1.setRxInvert(false);
 
+  log_d("Checking if Serial 1 TX can be inverted while running");
+  Serial1.setTxInvert(true);
+  Serial1.setTxInvert(false);
+
   Serial.println("Enabled UART calls test successful");
 }
 
@@ -351,6 +355,10 @@ void disabled_uart_calls_test(void) {
   Serial1.setRxInvert(true);
   Serial1.setRxInvert(false);
 
+  log_d("Checking if Serial 1 TX can be inverted when stopped");
+  Serial1.setTxInvert(true);
+  Serial1.setTxInvert(false);
+
   Serial.println("Disabled UART calls test successful");
 }