for #4154 use a binary gpio transformer to manage vext on heltec-tracker (saves power)

src/GpioLogic.cpp

@@ -12,6 +12,7 @@ void GpioVirtPin::set(bool value)
 
 void GpioHwPin::set(bool value)
 {
+    // if (num == 3) LOG_DEBUG("Setting pin %d to %d\n", num, value);
     pinMode(num, OUTPUT);
     digitalWrite(num, value);
 }
@@ -23,7 +24,7 @@ void GpioTransformer::set(bool value)
     outPin->set(value);
 }
 
-GpioNotTransformer::GpioNotTransformer(GpioVirtPin *inPin, GpioPin *outPin) : GpioTransformer(outPin), inPin(inPin)
+GpioUnaryTransformer::GpioUnaryTransformer(GpioVirtPin *inPin, GpioPin *outPin) : GpioTransformer(outPin), inPin(inPin)
 {
     assert(!inPin->dependentPin); // We only allow one dependent pin
     inPin->dependentPin = this;
@@ -33,6 +34,18 @@ GpioNotTransformer::GpioNotTransformer(GpioVirtPin *inPin, GpioPin *outPin) : Gp
     // update();
 }
 
+/**
+ * Update the output pin based on the current state of the input pin.
+ */
+void GpioUnaryTransformer::update()
+{
+    auto p = inPin->get();
+    if (p == GpioVirtPin::PinState::Unset)
+        return; // Not yet fully initialized
+
+    set(p);
+}
+
 /**
  * Update the output pin based on the current state of the input pin.
  */
@@ -75,6 +88,7 @@ void GpioBinaryTransformer::update()
             newValue = (GpioVirtPin::PinState)(p1 && p2);
             break;
         case Or:
+            // LOG_DEBUG("Doing GPIO OR\n");
             newValue = (GpioVirtPin::PinState)(p1 || p2);
             break;
         case Xor:

src/GpioLogic.h

@@ -42,7 +42,7 @@ class GpioBinaryTransformer;
 class GpioVirtPin : public GpioPin
 {
     friend class GpioBinaryTransformer;
-    friend class GpioNotTransformer;
+    friend class GpioUnaryTransformer;
 
   public:
     enum PinState { On = true, Off = false, Unset = 2 };
@@ -79,12 +79,31 @@ class GpioTransformer
 };
 
 /**
- * A transformer that performs a unary NOT operation from an input.
+ * A transformer that just drives a hw pin based on a virtual pin.
  */
-class GpioNotTransformer : public GpioTransformer
+class GpioUnaryTransformer : public GpioTransformer
 {
   public:
-    GpioNotTransformer(GpioVirtPin *inPin, GpioPin *outPin);
+    GpioUnaryTransformer(GpioVirtPin *inPin, GpioPin *outPin);
+
+  protected:
+    friend class GpioVirtPin;
+
+    /**
+     * Update the output pin based on the current state of the input pin.
+     */
+    virtual void update();
+
+    GpioVirtPin *inPin;
+};
+
+/**
+ * A transformer that performs a unary NOT operation from an input.
+ */
+class GpioNotTransformer : public GpioUnaryTransformer
+{
+  public:
+    GpioNotTransformer(GpioVirtPin *inPin, GpioPin *outPin) : GpioUnaryTransformer(inPin, outPin) {}
 
   protected:
     friend class GpioVirtPin;
@@ -93,9 +112,6 @@ class GpioNotTransformer : public GpioTransformer
      * Update the output pin based on the current state of the input pin.
      */
     void update();
-
-  private:
-    GpioVirtPin *inPin;
 };
 
 /**

src/gps/GPS.cpp

@@ -1415,19 +1415,18 @@ GPS *GPS::createGps()
     new_gps->rx_gpio = _rx_gpio;
     new_gps->tx_gpio = _tx_gpio;
 
+    GpioVirtPin *virtPin = new GpioVirtPin();
+    new_gps->enablePin = virtPin; // Always at least populate a virtual pin
     if (_en_gpio) {
         GpioPin *p = new GpioHwPin(_en_gpio);
 
         if (!GPS_EN_ACTIVE) { // Need to invert the pin before hardware
-            auto virtPin = new GpioVirtPin();
             new GpioNotTransformer(
                 virtPin, p); // We just leave this created object on the heap so it can stay watching virtPin and driving en_gpio
-            p = virtPin;
+        } else {
+            new GpioUnaryTransformer(
+                virtPin, p); // We just leave this created object on the heap so it can stay watching virtPin and driving en_gpio
         }
-        new_gps->enablePin = p;
-    } else {
-        // Just use a simulated pin
-        new_gps->enablePin = new GpioVirtPin();
     }
 
 #ifdef PIN_GPS_PPS

src/gps/GPS.h

@@ -157,7 +157,7 @@ class GPS : private concurrency::OSThread
      *
      * Normally set by GPS::createGPS()
      */
-    GpioPin *enablePin;
+    GpioVirtPin *enablePin;
 
     GPS() : concurrency::OSThread("GPS") {}
 

src/graphics/TFTDisplay.cpp

@@ -25,6 +25,8 @@ extern SX1509 gpioExtender;
 #define TFT_INVERT true
 #endif
 
+GpioPin *TFTDisplay::backlightEnable;
+
 class LGFX : public lgfx::LGFX_Device
 {
     lgfx::Panel_ST7735S _panel_instance;
@@ -584,6 +586,7 @@ void TFTDisplay::sendCommand(uint8_t com)
     // handle display on/off directly
     switch (com) {
     case DISPLAYON: {
+        // LOG_DEBUG("Display on\n");
         backlightEnable->set(true);
 #if ARCH_PORTDUINO
         display(true);
@@ -607,6 +610,7 @@ void TFTDisplay::sendCommand(uint8_t com)
         break;
     }
     case DISPLAYOFF: {
+        // LOG_DEBUG("Display off\n");
         backlightEnable->set(false);
 #if ARCH_PORTDUINO
         tft->clear();

src/graphics/TFTDisplay.h

@@ -43,8 +43,10 @@ class TFTDisplay : public OLEDDisplay
     /**
      * This is normally managed entirely by TFTDisplay, but some rare applications (heltec tracker) might need to replace the
      * default GPIO behavior with something a bit more complex.
+     *
+     * We (cruftily) make it static so that variant.cpp can access it without needing a ptr to the TFTDisplay instance.
      */
-    GpioPin *backlightEnable;
+    static GpioPin *backlightEnable;
 
   protected:
     // the header size of the buffer used, e.g. for the SPI command header