Interrupt issue with FastLed circumvented

Gaugecontroller/Gaugecontroller.ino

@@ -85,6 +85,7 @@ String rxLine;
 CRGB leds[TOTAL_LEDS];
 uint8_t gaugeLedOffset[GAUGE_COUNT];
 BlinkState blinkState[TOTAL_LEDS];
+bool ledsDirty = false;
 
 void sendReply(const String& s) {
   CMD_PORT.println(s);
@@ -545,7 +546,7 @@ bool parseLed(const String& line) {
       blinkState[gaugeLedOffset[id] + i].active = false;
       leds[gaugeLedOffset[id] + i] = color;
     }
-    FastLED.show();
+    ledsDirty = true;
     sendReply("OK");
     return true;
   }
@@ -553,10 +554,15 @@ bool parseLed(const String& line) {
 }
 
 bool parseBlink(const String& line) {
-  int id;
+  int id, onMs, offMs, r, g, b;
   char idxToken[16];
-  long onMs, offMs;
+  // Accept both forms:
-  if (sscanf(line.c_str(), "BLINK %d %15s %ld %ld", &id, idxToken, &onMs, &offMs) == 4) {
+  //   BLINK <id> <idx> <on_ms> <off_ms>           — use current LED colour
+  //   BLINK <id> <idx> <on_ms> <off_ms> <r> <g> <b> — set colour in same command
+  int count = sscanf(line.c_str(), "BLINK %d %15s %d %d %d %d %d",
+                     &id, idxToken, &onMs, &offMs, &r, &g, &b);
+  if (count != 4 && count != 7) return false;
+
   if (id < 0 || id >= GAUGE_COUNT) { sendReply("ERR BAD_ID"); return true; }
   char* dash = strchr(idxToken, '-');
   int idxFirst = atoi(idxToken);
@@ -573,11 +579,15 @@ bool parseBlink(const String& line) {
   }
   if (onMs <= 0 || offMs <= 0) { sendReply("ERR BAD_TIME"); return true; }
 
+  CRGB color = (count == 7)
+    ? CRGB(constrain(r, 0, 255), constrain(g, 0, 255), constrain(b, 0, 255))
+    : CRGB(0, 0, 0);  // placeholder; overwritten per-LED below when count==4
+
   unsigned long nowMs = millis();
   for (int i = idxFirst; i <= idxLast; i++) {
     uint8_t globalIdx = gaugeLedOffset[id] + i;
     BlinkState& bs = blinkState[globalIdx];
-      bs.onColor = leds[globalIdx];
+    bs.onColor  = (count == 7) ? color : leds[globalIdx];
     bs.onMs     = (uint32_t)onMs;
     bs.offMs    = (uint32_t)offMs;
     bs.currentlyOn  = true;
@@ -585,12 +595,10 @@ bool parseBlink(const String& line) {
     bs.active   = true;
     leds[globalIdx] = bs.onColor;
   }
-    FastLED.show();
+  ledsDirty = true;
   sendReply("OK");
   return true;
 }
-  return false;
-}
 
 void updateBlink() {
   unsigned long nowMs = millis();
@@ -612,7 +620,7 @@ void updateBlink() {
     }
   }
 
-  if (changed) FastLED.show();
+  if (changed) ledsDirty = true;
 }
 
 void processLine(const String& line) {
@@ -691,6 +699,11 @@ void loop() {
   readCommands();
   updateBlink();
 
+  if (ledsDirty) {
+    FastLED.show();
+    ledsDirty = false;
+  }
+
   for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
     updateGauge(i);
   }

gauge.py

@@ -224,12 +224,15 @@ def set_status_led(gauge_idx, led_type, on):
 
 
 def _apply_blink_or_led(gauge_idx, led_idx, color, effect):
-    """Set LED to color; if effect is a known blink preset, start blinking."""
+    """Set LED to color, optionally starting a blink effect.
+    When blinking, color is passed inside the BLINK command so only one
+    serial command is needed — avoids a FastLED.show() race on the Arduino."""
     r, g, b = color
-    arduino_send(f"LED {gauge_idx} {led_idx} {r} {g} {b}")
     if effect in _BLINK_PRESETS:
         on_ms, off_ms = _BLINK_PRESETS[effect]
-        arduino_send(f"BLINK {gauge_idx} {led_idx} {on_ms} {off_ms}")
+        arduino_send(f"BLINK {gauge_idx} {led_idx} {on_ms} {off_ms} {r} {g} {b}")
+    else:
+        arduino_send(f"LED {gauge_idx} {led_idx} {r} {g} {b}")
 
 
 # ---------------------------------------------------------------------------
@@ -553,12 +556,13 @@ def on_message(topic, payload):
                 return
             _bl_effect[i] = effect
             if effect:
-                set_backlight(i, r, g, b, brightness)
+                scale = brightness / 100
+                rs = int(r * scale); gs = int(g * scale); bs_ = int(b * scale)
+                on_ms, off_ms = _BLINK_PRESETS[effect]
+                arduino_send(f"BLINK {i} {_LED_BACKLIGHT_RANGE} {on_ms} {off_ms} {rs} {gs} {bs_}")
                 backlight_color[i] = (r, g, b)
                 backlight_brightness[i] = brightness
                 backlight_on[i] = True
-                on_ms, off_ms = _BLINK_PRESETS[effect]
-                arduino_send(f"BLINK {i} {_LED_BACKLIGHT_RANGE} {on_ms} {off_ms}")
                 _mark_bl_dirty()
             else:
                 set_backlight_color(i, r, g, b, brightness)