companion: keep mesh/BLE running during e-ink refresh

examples/companion_radio/main.cpp

@@ -132,6 +132,10 @@ void halt() {
   bool wifi_enabled = false;   // set at boot from prefs; false also when the effective SSID is blank
 #endif
 
+#if defined(DISPLAY_CLASS) && defined(EINK_REFRESH_LOOP)
+static void loopDuringDisplayRefresh();
+#endif
+
 void setup() {
   Serial.begin(115200);
   board.begin();
@@ -284,15 +288,36 @@ void setup() {
 #ifdef DISPLAY_CLASS
   ui_task.begin(disp, &sensors, the_mesh.getNodePrefs());  // still want to pass this in as dependency, as prefs might be moved
   the_mesh.setListener(&ui_task);
+#ifdef EINK_REFRESH_LOOP
+  if (disp != NULL) disp->setBusyHook(loopDuringDisplayRefresh);
+#endif
 #endif
 
   board.onBootComplete();
 }
 
-void loop() {
+// Work that must keep running even while the UI is blocked (e.g. by an e-ink refresh).
+// Called from loop() and from the display busy hook, so both always run the same set.
+static void loopCore() {
   the_mesh.loop();
   interface_manager.loop();
   sensors.loop();
+}
+
+#if defined(DISPLAY_CLASS) && defined(EINK_REFRESH_LOOP)
+// Runs from inside the e-ink busy wait, so radio/BLE/sensors keep going during a panel refresh.
+// Must not touch the display: UI listener callbacks only update state and schedule the next frame.
+static void loopDuringDisplayRefresh() {
+  static bool active = false;
+  if (active) return;
+  active = true;
+  loopCore();
+  active = false;
+}
+#endif
+
+void loop() {
+  loopCore();
 #ifdef DISPLAY_CLASS
   ui_task.loop();
 #endif

src/helpers/ui/DisplayDriver.h

@@ -24,6 +24,7 @@ class DisplayDriver {
   virtual bool isOn() = 0;
   virtual bool isEink() { return false; } // default to non-eink, override in eink drivers
   virtual void forceFullRefresh() {} // next refresh will be full for eink
+  virtual void setBusyHook(void (*hook)()) {} // eink: hook is called repeatedly while waiting for panel refresh
   virtual void turnOn() = 0;
   virtual void turnOn(int max_partial) { turnOn(); }
   virtual void turnOff() = 0;

src/helpers/ui/GxEPDDisplay.cpp

@@ -88,7 +88,9 @@ void GxEPDDisplay::drawSleepIcon() {
   display.fillRect((x - 5) * scale_x - 1, y * scale_y, (W+5) * scale_x + 2, (H-2) * scale_y + 1, GxEPD_WHITE);
   _curr_color = GxEPD_BLACK;
   drawXbm(x, y, sleep_icon_24x24, W, H);
+  if (_busy_hook) display.epd2.setBusyCallback(busyCallback, this);
   display.display(true);
+  display.epd2.setBusyCallback(NULL);
 }
 
 void GxEPDDisplay::turnOff(bool blank) {
@@ -104,8 +106,10 @@ void GxEPDDisplay::turnOff(bool blank) {
 void GxEPDDisplay::blankScreen() {
   // do full refresh before powering off to clear screen
   // no full refresh needed at wakeup
+  if (_busy_hook) display.epd2.setBusyCallback(busyCallback, this);
   display.clearScreen(0xFF); // Clears microcontroller side RAM
   display.writeScreenBuffer(0xFF); // Forces 0xFF (White) into the display controller's history registers
+  display.epd2.setBusyCallback(NULL);
   _partial_refresh_count = 0;
   last_display_crc_value = 0;
   // we can hibernate as screen has been cleaned
@@ -126,8 +130,10 @@ void GxEPDDisplay::startFrame(ColorVal bkg) {
       || (_max_partial_refresh > 0 
           && _partial_refresh_count >= _max_partial_refresh)) {
     // forces a full wipe of the screen ...
+    if (_busy_hook) display.epd2.setBusyCallback(busyCallback, this);
     display.clearScreen(0xFF); // Clears microcontroller side RAM
     display.writeScreenBuffer(0xFF); // Forces 0xFF (White) into the display controller's history registers
+    display.epd2.setBusyCallback(NULL);
     // we'll need a partial refresh after that (whatever crc value is)
     last_display_crc_value = 0;
     _partial_refresh_count = 0;
@@ -239,7 +245,10 @@ void GxEPDDisplay::endFrame() {
   if (_isOn == false) return;
   uint32_t crc = display_crc.finalize();
   if (crc != last_display_crc_value) {
+    // keep the rest of the firmware running while the panel refreshes (~0.5s partial)
+    if (_busy_hook) display.epd2.setBusyCallback(busyCallback, this);
     display.display(true);
+    display.epd2.setBusyCallback(NULL);
     _partial_refresh_count++;
   }
   last_display_crc_value = crc;

src/helpers/ui/GxEPDDisplay.h

@@ -39,6 +39,12 @@ class GxEPDDisplay : public DisplayDriver {
   bool _force_full_refresh = false;
   int _partial_refresh_count = 0;
   int _max_partial_refresh = 0;
+  void (*_busy_hook)() = NULL;
+
+  static void busyCallback(const void* self) {
+    ((const GxEPDDisplay*)self)->_busy_hook();
+    delay(1);  // same as GxEPD2 does without a callback
+  }
 
 public:
 #if defined(EINK_DISPLAY_MODEL)
@@ -53,6 +59,7 @@ class GxEPDDisplay : public DisplayDriver {
   bool isEink() override { return true; }
   void forceFullRefresh() override { _force_full_refresh = true; }
   void turnOn(int max_partial) override;
+  void setBusyHook(void (*hook)()) override { _busy_hook = hook; }
   void turnOn() override;
   void turnOff(bool blank) override;
   void turnOff() override { turnOff(false); }

variants/lilygo_techo/platformio.ini

@@ -93,6 +93,7 @@ build_flags =
   ${LilyGo_T-Echo.build_flags}
   -I src/helpers/ui
   -I examples/companion_radio/ui-new
+  -D EINK_REFRESH_LOOP
   -D MAX_CONTACTS=350
   -D MAX_GROUP_CHANNELS=40
   -D QSPIFLASH=1
@@ -120,6 +121,7 @@ build_flags =
   ${LilyGo_T-Echo.build_flags}
   -I src/helpers/ui
   -I examples/companion_radio/ui-new
+  -D EINK_REFRESH_LOOP
   -D MAX_CONTACTS=350
   -D MAX_GROUP_CHANNELS=40
   -D OFFLINE_QUEUE_SIZE=256