fix ble connection , ok !

include/DisplayManager.h

@@ -23,10 +23,11 @@
 #include <Fonts/FreeMonoBold12pt7b.h>
 #include <Fonts/FreeMono9pt7b.h>
 
-// ── Display model — Waveshare 4.2" mono GDEY042T81 (400×300) ─────────────────
-// Adjust the model constant if your display differs.
-using DisplayType = GxEPD2_BW<GxEPD2_420_GDEY042T81,
-                               GxEPD2_420_GDEY042T81::HEIGHT>;
+// ── Display model — match the validated reference sketch for the 4.2" panel.
+// The generic 420 driver is used here to avoid a controller mismatch that can
+// leave the panel completely blank during init.
+using DisplayType = GxEPD2_BW<GxEPD2_420,
+                               GxEPD2_420::HEIGHT>;
 
 class DisplayManager {
 public:
@@ -70,10 +71,10 @@ public:
 
 private:
     DisplayType _display {
-        GxEPD2_420_GDEY042T81(Pins::EPD_CS,
-                               Pins::EPD_DC,
-                               Pins::EPD_RST,
-                               Pins::EPD_BUSY)
+        GxEPD2_420(Pins::EPD_CS,
+                   Pins::EPD_DC,
+                   Pins::EPD_RST,
+                   Pins::EPD_BUSY)
     };
 
     bool     _initialised     = false;