feat(ecg): lock mode/bias while logging

preload/apps/ecg/__init__.py

@@ -183,14 +183,28 @@ def close_sensor():
 
 
 def toggle_mode():
-    global current_mode
+    global current_mode, disp, pause_screen
+    if write > 0:
+        pause_screen = utime.time_ms() + 500
+        disp.clear(COLOR_BACKGROUND)
+        disp.print("Locked", posx=30, posy=30, fg=COLOR_TEXT)
+        disp.update()
+        return
+
     close_sensor()
     current_mode = MODE_USB if current_mode == MODE_FINGER else MODE_FINGER
     open_sensor()
 
 
 def toggle_bias():
-    global bias
+    global bias, disp, pause_screen
+    if write > 0:
+        pause_screen = utime.time_ms() + 500
+        disp.clear(COLOR_BACKGROUND)
+        disp.print("Locked", posx=30, posy=30, fg=COLOR_TEXT)
+        disp.update()
+        return
+
     close_sensor()
     bias = not bias
     open_sensor()