Add support for reverse numbering of analog pins. (earlephilhower#283)

Author: PontusO

cores/rp2040/wiring_analog.cpp

@@ -121,15 +121,18 @@ auto_init_mutex(_adcMutex);
 extern "C" int analogRead(pin_size_t pin) {
     CoreMutex m(&_adcMutex);
 
-    if ((pin < A0) || (pin > A3) || !m) {
+    pin_size_t maxPin = max(A0, A3);
+    pin_size_t minPin = min(A0, A3);
+
+    if ((pin < minPin) || (pin > maxPin) || !m) {
         DEBUGCORE("ERROR: Illegal analogRead pin (%d)\n", pin);
         return 0;
     }
     if (!adcInitted) {
         adc_init();
     }
     adc_gpio_init(pin);
-    adc_select_input(pin - A0);
+    adc_select_input(pin - minPin);
     return adc_read();
 }
 

variants/challenger_2040_lte/pins_arduino.h

@@ -67,9 +67,9 @@ static const uint8_t D15 =  (14u);
 static const uint8_t D16 =  (15u);
 static const uint8_t D17 =  (19u);
 
-static const uint8_t A0 =   (26u);
-static const uint8_t A1 =   (27u);
-static const uint8_t A2 =   (28u);
-static const uint8_t A3 =   (29u);
+static const uint8_t A0 =   (29u);
+static const uint8_t A1 =   (28u);
+static const uint8_t A2 =   (27u);
+static const uint8_t A3 =   (26u);
 static const uint8_t A4 =   (25u);
 static const uint8_t A5 =   (21u);