LED now accepts ranges

CLAUDE.md

@@ -16,6 +16,40 @@ arduino-cli upload -p /dev/ttyACM0 --fqbn arduino:avr:mega Gaugecontroller.ino
 
 Serial monitor: 115200 baud (`Serial` is both CMD_PORT and DEBUG_PORT).
 
+## Switching serial ports (debug → production)
+
+Two `#define`s at the top of `Gaugecontroller.ino` control where commands and debug output go:
+
+```cpp
+#define CMD_PORT   Serial   // command channel (host sends SET, HOME, etc.)
+#define DEBUG_PORT Serial   // diagnostic prints (homing, boot messages)
+```
+
+**Debug / USB-only (default):** both point to `Serial` (the USB-CDC port). Connect via `minicom` or the Arduino IDE serial monitor at 115200 baud.
+
+**Production (hardware UART):** change `CMD_PORT` to a hardware serial port so a host MCU or Raspberry Pi can drive it without occupying the USB port:
+
+```cpp
+#define CMD_PORT   Serial1  // TX1=pin18, RX1=pin19
+#define DEBUG_PORT Serial   // keep USB for monitoring, or silence it (see below)
+```
+
+Arduino Mega hardware UARTs:
+
+| Port    | TX pin | RX pin |
+|---------|--------|--------|
+| Serial1 | 18     | 19     |
+| Serial2 | 16     | 17     |
+| Serial3 | 14     | 15     |
+
+`setup()` calls `DEBUG_PORT.begin(115200)` only. If `CMD_PORT` differs from `DEBUG_PORT` you must also begin it — add a second `begin` call in `setup()`:
+
+```cpp
+CMD_PORT.begin(115200);
+```
+
+**Silencing debug output entirely:** point `DEBUG_PORT` at a null stream, or wrap all `DEBUG_PORT` calls in an `#ifdef DEBUG` guard. The simplest option is to replace the define with a no-op object, but the easiest production approach is just to leave `DEBUG_PORT Serial` and ignore the USB output.
+
 ## Architecture
 
 The sketch controls `GAUGE_COUNT` stepper-motor gauges using a trapezoidal velocity profile and a simple text serial protocol.
@@ -56,7 +90,7 @@ Commands arrive as newline-terminated ASCII lines. Each `parse*` function in `pr
 | `HOME` | `HOME <id>` / `HOMEALL` | Run homing sequence |
 | `SWEEP` | `SWEEP <id> <accel> <speed>` | Start sweep (0/0 stops) |
 | `POS?` | `POS?` | Query all gauges: `POS <id> <cur> <tgt> <homed> <homingState> <sweep>` |
-| `LED` | `LED <id> <idx> <r> <g> <b>` | Set one LED (0-based index within gauge segment) to RGB colour (0–255 each) |
+| `LED` | `LED <id> <idx> <r> <g> <b>` | Set one LED (0-based index within gauge segment) to RGB colour (0–255 each); `<idx>` may be a range `N-M` to set LEDs N through M in one command |
 | `LED?` | `LED?` | Query all LEDs: one `LED <id> <idx> <r> <g> <b>` line per LED, then `OK` |
 | `PING` | `PING` | Responds `PONG` |
 

Gaugecontroller/Gaugecontroller.ino

@@ -520,13 +520,19 @@ bool parseLedQuery(const String& line) {
 }
 
 bool parseLed(const String& line) {
-  int id, idx, r, g, b;
-  if (sscanf(line.c_str(), "LED %d %d %d %d %d", &id, &idx, &r, &g, &b) == 5) {
+  int id, r, g, b;
+  char idxToken[16];
+  if (sscanf(line.c_str(), "LED %d %15s %d %d %d", &id, idxToken, &r, &g, &b) == 5) {
     if (id < 0 || id >= GAUGE_COUNT) { sendReply("ERR BAD_ID"); return true; }
-    if (idx < 0 || idx >= gaugePins[id].ledCount) { sendReply("ERR BAD_IDX"); return true; }
-    leds[gaugeLedOffset[id] + idx] = CRGB(constrain(r, 0, 255),
-                                          constrain(g, 0, 255),
-                                          constrain(b, 0, 255));
+    char* dash = strchr(idxToken, '-');
+    int idxFirst = atoi(idxToken);
+    int idxLast  = dash ? atoi(dash + 1) : idxFirst;
+    if (idxFirst < 0 || idxLast >= gaugePins[id].ledCount || idxFirst > idxLast) {
+      sendReply("ERR BAD_IDX"); return true;
+    }
+    CRGB color(constrain(r, 0, 255), constrain(g, 0, 255), constrain(b, 0, 255));
+    for (int i = idxFirst; i <= idxLast; i++)
+      leds[gaugeLedOffset[id] + i] = color;
     FastLED.show();
     sendReply("OK");
     return true;