Added a function to allow inverting the output from a GPIO pin

cores/rp2040/Arduino.h

@@ -105,6 +105,9 @@ void analogWriteFreq(uint32_t freq);
 void analogWriteRange(uint32_t range);
 void analogWriteResolution(int res);
 
+// GPIO RP2040-specific calls
+void setPinInvert(pin_size_t ulPin, bool invert);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif

cores/rp2040/wiring_digital.cpp

@@ -25,13 +25,27 @@ extern void __clearADCPin(pin_size_t p);
 
 static PinMode _pm[__GPIOCNT];
 
+extern "C" void setPinInvert(pin_size_t ulPin, bool invert) __attribute__((weak, alias("__setPinInvert")));
+extern "C" void __setPinInvert(pin_size_t ulPin, bool invert) {
+    if (ulPin >= __GPIOCNT) {
+        DEBUGCORE("ERROR: Illegal pin in setPinInvert (%d)\n", ulPin);
+        return;
+    }
+
+    if (invert)
+        gpio_set_outover(ulPin, GPIO_OVERRIDE_INVERT);
+    else
+        gpio_set_outover(ulPin, GPIO_OVERRIDE_NORMAL);
+}
+
 extern "C" void pinMode(pin_size_t ulPin, PinMode ulMode) __attribute__((weak, alias("__pinMode")));
 extern "C" void __pinMode(pin_size_t ulPin, PinMode ulMode) {
     if (ulPin >= __GPIOCNT) {
         DEBUGCORE("ERROR: Illegal pin in pinMode (%d)\n", ulPin);
         return;
     }
-
+
+    gpio_set_function(ulPin, GPIO_FUNC_SIO);
     switch (ulMode) {
     case INPUT:
         gpio_init(ulPin);
@@ -90,7 +104,6 @@ extern "C" void __digitalWrite(pin_size_t ulPin, PinStatus ulVal) {
         DEBUGCORE("ERROR: Illegal pin in pinMode (%d)\n", ulPin);
         return;
     }
-    gpio_set_function(ulPin, GPIO_FUNC_SIO);
     if (_pm[ulPin] == INPUT_PULLDOWN) {
         if (ulVal == LOW) {
             gpio_set_dir(ulPin, false);

docs/digital.rst

@@ -18,6 +18,34 @@ Output Modes (Pad Strength)
 ---------------------------
 The Raspberry Pi Pico has the ability to set the current that a pin (actually the pad associated with it) is capable of supplying. The current can be set to values of 2mA, 4mA, 8mA and 12mA. By default, on a reset, the setting is 4mA. A `pinMode(x, OUTPUT)`, where `x` is the pin number, is also the default setting. 4 settings have been added for use with `pinMode`: `OUTPUT_2MA`, `OUTPUT_4MA`, which has the same behavior as `OUTPUT`, `OUTPUT_8MA` and `OUTPUT_12MA`.
 
+GPIO Output Inversion
+---------------------
+The RP2040 and RP2350 microcontrollers support configurable output inversion on all GPIO pins.
+This feature allows each GPIO to output either the logical value or its inverted equivalent,
+without requiring changes to the underlying logic of your application.
+
+This is especially useful when adapting existing libraries or hardware that use opposite logic levels.
+By configuring inversion at the GPIO level, you can achieve compatibility without rewriting code.
+
+Function
+--------
+
+.. code-block:: c
+
+   void setPinInvert(uint pin, bool invert);
+
+**Parameters:**
+
+- ``pin``: The GPIO number to configure.
+- ``invert``:
+
+  - ``true`` — Enables output inversion (logical 1 becomes 0, and vice versa).
+  - ``false`` — Disables inversion, restoring default non-inverted output.
+
+.. note::
+
+   All GPIO pins are configured as non-inverting outputs by default.
+
 Tone/noTone
 -----------
 Simple square wave tone generation is possible for up to 8 channels using

libraries/rp2040/examples/GPIOInvert/GPIOInvert.ino

@@ -0,0 +1,37 @@
+
+/*
+  GPIOInvert
+
+  This example shows how to enable the pin output inversion mechanism for a GPIO pin.
+
+  This example code is in the public domain.
+*/
+
+int led = LED_BUILTIN; // the pin the LED is attached to
+
+// the setup routine runs once when you press reset:
+void setup() {
+  // declare pin to be an output:
+  pinMode(led, OUTPUT);
+  //  Now enable the pin inversion function. 
+  // This must be done after the pinMode command.
+  setPinInvert(led, true);
+
+  while(!Serial)
+    delay(10);
+
+  Serial.begin(115200);
+}
+
+// the loop routine runs over and over again forever:
+void loop() {
+    // Turn the LED off
+    digitalWrite(led, HIGH);
+    Serial.println("LED off");
+    delay(2000);
+
+    // Turn the LED on
+    digitalWrite(led, LOW);
+    Serial.println("LED on");
+    delay(2000);
+}