Support async full refresh in meshtastic/firmware

src/GxEPD2_BW.h

@@ -12,6 +12,11 @@
 #ifndef _GxEPD2_BW_H_
 #define _GxEPD2_BW_H_
 
+// This version of meshtastic/GxEPD2 has been modified (defiled) to allow nextPage() to run full refreshes asynchronously
+// This macro ensures that the relevant modifications to meshtastic/firmware will only run with a correctly modified version of GxEPD2
+// Note: this async behavior is unrelated to the callback system implemented in newer versions of ZinggJM/GxEPD2
+#define HAS_EINK_ASYNCFULL
+
 // uncomment next line to use class GFX of library GFX_Root instead of Adafruit_GFX
 //#include <GFX.h>
 
@@ -239,6 +244,16 @@ class GxEPD2_BW : public GxEPD2_GFX_BASE_CLASS
       _second_phase = false;
     }
 
+    // Transplanted from nextPage(), non-paged, full refresh
+    // This is the code which runs after the refresh() call
+    // Method is called by meshtastic/firmware, once polling GxEPD2_BW::isBusy() reports that the physical refresh is complete
+    void endAsyncFull() {
+      if (epd2.hasFastPartialUpdate) {
+        epd2.writeImageAgain(_buffer, 0, 0, WIDTH, HEIGHT);
+      }
+      epd2.powerOff();
+    }
+
     bool nextPage()
     {
       if (1 == _pages)
@@ -258,12 +273,16 @@ class GxEPD2_BW : public GxEPD2_GFX_BASE_CLASS
         {
           epd2.writeImageForFullRefresh(_buffer, 0, 0, WIDTH, HEIGHT);
           epd2.refresh(false);
+#if defined(USE_EINK_DYNAMICDISPLAY)   // This macro defined in meshtastic/firmware
+          // -- meshtastic: moved to endAsyncFull() --
+#else
           if (epd2.hasFastPartialUpdate)
           {
             epd2.writeImageAgain(_buffer, 0, 0, WIDTH, HEIGHT);
             //epd2.refresh(true); // not needed
           }
           epd2.powerOff();
+#endif
         }
         return false;
       }

src/GxEPD2_EPD.cpp

@@ -96,6 +96,10 @@ void GxEPD2_EPD::_reset()
 
 void GxEPD2_EPD::_waitWhileBusy(const char* comment, uint16_t busy_time)
 {
+  // For full refreshes, meshtastic/firmare will poll GxEPD2_EPD::isBusy() instead of waiting here
+  if (_isUpdatingFull(comment))
+    return;
+
   if (_busy >= 0)
   {
     delay(1); // add some margin to become active
@@ -241,3 +245,19 @@ void GxEPD2_EPD::_endTransfer()
   if (_cs >= 0) digitalWrite(_cs, HIGH);
   _spi.endTransaction();
 }
+
+// Polled by meshtastic/firmware, during async full-refresh
+bool GxEPD2_EPD::isBusy() {
+  return (digitalRead(_busy) == _busy_level);
+}
+
+// Used to skip _waitWhileBusy(), for meshtastic async
+bool GxEPD2_EPD::_isUpdatingFull(const char* comment) {
+  // On first update, a fast-refresh might also clear screen using a full-refresh
+  // If meshtastic/firmware asked for fast-refresh, it will expect this full-refresh to block. So: force that to happen
+  if (_initial_refresh)
+    return false;
+
+  // True if comment matches
+  return ( strcmp(comment, "_Update_Full") == 0 );
+}

src/GxEPD2_EPD.h

@@ -91,6 +91,7 @@ class GxEPD2_EPD
     {
       return (a > b ? a : b);
     };
+    bool isBusy();  // Used in meshtastic/firmware, to poll after nextPage(), for async full refresh
   protected:
     void _reset();
     void _waitWhileBusy(const char* comment = 0, uint16_t busy_time = 5000);
@@ -104,6 +105,7 @@ class GxEPD2_EPD
     void _startTransfer();
     void _transfer(uint8_t value);
     void _endTransfer();
+    bool _isUpdatingFull(const char* comment);  // Meshtastic: Determine if _waitWhileBusy() should be skipped (for async), by comparing the comment string..
   protected:
     int8_t _cs, _dc, _rst, _busy, _busy_level;
     uint32_t _busy_timeout;

src/epd/GxEPD2_213_FC1.cpp

@@ -38,6 +38,7 @@ void GxEPD2_213_FC1::clearScreen(uint8_t value)
   _writeScreenBuffer(0x13, value); // Clear "NEW" (red) mem
   _writeScreenBuffer(0x10, value); // Clear "OLD" (black) mem
   refresh(false); // Full refresh
+  _PowerOff();
   _initial_write = false;
   _initial_refresh = false;
 }