LED now accepts ranges

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Build & Upload
+
+This is a single-file Arduino sketch (`Gaugecontroller.ino`). Requires the **FastLED** library (`arduino-cli lib install FastLED`). Use the Arduino IDE or `arduino-cli`:
+
+```bash
+# Compile (replace board/port as needed)
+arduino-cli compile --fqbn arduino:avr:mega Gaugecontroller.ino
+
+# Upload
+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.
+
+### Key data structures
+
+- `GaugePins` — hardware pin mapping per gauge (dir, step, enable, active-high/low polarity flags, `ledCount`). Declared `constexpr` so `TOTAL_LEDS` can be computed from it at compile time. Configured in the `gaugePins[]` array at the top.
+- `Gauge` — per-gauge runtime state: position, target, velocity, accel, homing state machine, sweep mode.
+
+### Motion control (`updateGauge`)
+
+Each call to `updateGauge(id)` in `loop()` computes `dt` since last call and updates velocity using a braking-distance check to produce smooth trapezoidal motion. Steps are accumulated as floating-point and emitted via `doStep` when the accumulator crosses ±1.
+
+### Homing sequence (`updateHoming`)
+
+State machine: `HS_START → HS_BACKING → HS_SETTLE → HS_DONE → HS_IDLE`.  
+Backs up `homingBackoffSteps` at `homingSpeed`, waits 100 ms settle, then declares `currentPos = 0`. No physical end-stop is used; homing is purely time/step-count based.
+
+### Sweep mode
+
+When `sweepEnabled`, `updateSweepTarget` bounces `targetPos` between `minPos` and `maxPos` autonomously.
+
+### LED strip
+
+One shared WS2812B strip is driven from `LED_DATA_PIN` (default 6). Each gauge owns a contiguous segment of the strip; `gaugePins[i].ledCount` sets the segment length (0 = no LEDs). `TOTAL_LEDS` is computed at compile time via `constexpr sumLedCounts()` — no manual constant to keep in sync. Per-gauge offsets into the flat `leds[]` array are computed once in `setup()` into `gaugeLedOffset[]`. `FastLED.show()` is called immediately after each `LED` command.
+
+### Serial command protocol
+
+Commands arrive as newline-terminated ASCII lines. Each `parse*` function in `processLine` handles one command family:
+
+| Command | Syntax | Effect |
+|---|---|---|
+| `SET` | `SET <id> <pos>` | Move gauge to absolute step position |
+| `SPEED` | `SPEED <id> <steps/s>` | Set max speed |
+| `ACCEL` | `ACCEL <id> <steps/s²>` | Set acceleration |
+| `ENABLE` | `ENABLE <id> <0\|1>` | Enable/disable driver output |
+| `ZERO` | `ZERO <id>` | Mark current position as home without moving |
+| `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); `<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` |
+
+All commands reply `OK` or `ERR BAD_ID` / `ERR BAD_CMD` etc.
+
+### Adding gauges
+
+1. Increment `GAUGE_COUNT`.
+2. Add a `constexpr GaugePins` entry to `gaugePins[]` (including `ledCount`).
+3. Tune `maxPos` and `homingBackoffSteps` in the corresponding `Gauge` default or at runtime.
+4. `TOTAL_LEDS` and `gaugeLedOffset[]` update automatically — no manual changes needed.

Gaugecontroller/Gaugecontroller.ino

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+#include <Arduino.h>
+#include <math.h>
+#include <FastLED.h>
+
+static const uint8_t GAUGE_COUNT = 2;
+
+// LED strip — one shared WS2812B strip, segmented per gauge.
+// Set LED_DATA_PIN to the digital pin driving the strip data line.
+// TOTAL_LEDS is computed automatically from gaugePins[].ledCount.
+static const uint8_t LED_DATA_PIN = 22;
+
+// For now: commands come over USB serial
+#define CMD_PORT Serial
+#define DEBUG_PORT Serial
+
+struct GaugePins {
+  uint8_t dirPin;
+  uint8_t stepPin;
+  int8_t enablePin;          // -1 if unused
+  bool dirInverted;
+  bool stepActiveHigh;
+  bool enableActiveLow;
+  uint8_t ledCount;          // WS2812B LEDs on this gauge's strip segment (0 if none)
+};
+
+constexpr GaugePins gaugePins[GAUGE_COUNT] = {
+  // dir, step, en, dirInv, stepHigh, enActiveLow, leds
+  {50, 51, -1, false, true, true, 6},   // Gauge 0
+  {8,  9,  -1, true,  true, true, 6},   // Gauge 1
+};
+
+constexpr uint8_t sumLedCounts(uint8_t i = 0) {
+  return i >= GAUGE_COUNT ? 0 : gaugePins[i].ledCount + sumLedCounts(i + 1);
+}
+static const uint8_t TOTAL_LEDS = sumLedCounts();
+
+enum HomingState : uint8_t {
+  HS_IDLE,
+  HS_START,
+  HS_BACKING,
+  HS_SETTLE,
+  HS_DONE
+};
+
+struct Gauge {
+  long currentPos = 0;
+  long targetPos = 0;
+
+  long minPos = 0;
+  long maxPos = 3610;             // adjust to your usable travel
+  long homingBackoffSteps = 3700; // should exceed reverse travel slightly
+
+  float velocity = 0.0f;
+  float maxSpeed = 5000.0f;
+  float accel = 6000.0f;
+  float homingSpeed = 500.0f;
+
+  float stepAccumulator = 0.0f;
+  unsigned long lastUpdateMicros = 0;
+
+  bool enabled = true;
+  bool homed = false;
+
+  HomingState homingState = HS_IDLE;
+  long homingStepsRemaining = 0;
+  unsigned long homingLastStepMicros = 0;
+  unsigned long homingStateStartMs = 0;
+
+  bool sweepEnabled = false;
+  bool sweepTowardMax = true;
+};
+
+Gauge gauges[GAUGE_COUNT];
+String rxLine;
+
+CRGB leds[TOTAL_LEDS];
+uint8_t gaugeLedOffset[GAUGE_COUNT];
+
+void sendReply(const String& s) {
+  CMD_PORT.println(s);
+}
+
+float absf(float x) {
+  return (x < 0.0f) ? -x : x;
+}
+
+void setEnable(uint8_t id, bool en) {
+  if (id >= GAUGE_COUNT) return;
+  gauges[id].enabled = en;
+
+  int8_t pin = gaugePins[id].enablePin;
+  if (pin < 0) return;
+
+  bool level = gaugePins[id].enableActiveLow ? !en : en;
+  digitalWrite(pin, level ? HIGH : LOW);
+}
+
+void setDir(uint8_t id, bool forward) {
+  bool level = gaugePins[id].dirInverted ? !forward : forward;
+  digitalWrite(gaugePins[id].dirPin, level ? HIGH : LOW);
+}
+
+void pulseStep(uint8_t id) {
+  bool active = gaugePins[id].stepActiveHigh;
+  digitalWrite(gaugePins[id].stepPin, active ? HIGH : LOW);
+  delayMicroseconds(4);
+  digitalWrite(gaugePins[id].stepPin, active ? LOW : HIGH);
+}
+
+void doStep(uint8_t id, int dir, bool allowPastMin = false) {
+  Gauge& g = gauges[id];
+  if (!g.enabled) return;
+
+  if (dir > 0) {
+    if (g.currentPos >= g.maxPos) return;
+    setDir(id, true);
+    pulseStep(id);
+    g.currentPos++;
+  } else if (dir < 0) {
+    if (!allowPastMin && g.currentPos <= g.minPos) return;
+    setDir(id, false);
+    pulseStep(id);
+    g.currentPos--;
+  }
+}
+
+void requestHome(uint8_t id) {
+  if (id >= GAUGE_COUNT) return;
+  Gauge& g = gauges[id];
+  g.homingState = HS_START;
+  g.homed = false;
+  g.velocity = 0.0f;
+  g.stepAccumulator = 0.0f;
+  g.sweepEnabled = false;
+}
+
+void requestHomeAll() {
+  for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
+    requestHome(i);
+  }
+}
+
+void updateHoming(uint8_t id) {
+  Gauge& g = gauges[id];
+  unsigned long nowUs = micros();
+  unsigned long nowMs = millis();
+
+  switch (g.homingState) {
+    case HS_IDLE:
+      return;
+
+    case HS_START:
+      g.velocity = 0.0f;
+      g.stepAccumulator = 0.0f;
+      g.homingStepsRemaining = g.homingBackoffSteps;
+      g.homingLastStepMicros = nowUs;
+      g.homingState = HS_BACKING;
+      break;
+
+    case HS_BACKING: {
+      float intervalUs = 1000000.0f / g.homingSpeed;
+      if ((nowUs - g.homingLastStepMicros) >= intervalUs) {
+        g.homingLastStepMicros = nowUs;
+
+        if (g.homingStepsRemaining > 0) {
+          doStep(id, -1, true);
+          g.homingStepsRemaining--;
+        } else {
+          g.homingState = HS_SETTLE;
+          g.homingStateStartMs = nowMs;
+        }
+      }
+      break;
+    }
+
+    case HS_SETTLE:
+      if (nowMs - g.homingStateStartMs >= 100) {
+        g.currentPos = 0;
+        g.targetPos = 0;
+        g.velocity = 0.0f;
+        g.stepAccumulator = 0.0f;
+        g.homed = true;
+        g.homingState = HS_DONE;
+
+        DEBUG_PORT.print("HOMED ");
+        DEBUG_PORT.println(id);
+      }
+      break;
+
+    case HS_DONE:
+      g.homingState = HS_IDLE;
+      break;
+  }
+}
+
+void updateSweepTarget(uint8_t id) {
+  Gauge& g = gauges[id];
+  if (!g.sweepEnabled || !g.homed || g.homingState != HS_IDLE) return;
+
+  if (g.sweepTowardMax) {
+    g.targetPos = g.maxPos;
+    if (g.currentPos >= g.maxPos && absf(g.velocity) < 1.0f) {
+      g.sweepTowardMax = false;
+      g.targetPos = g.minPos;
+    }
+  } else {
+    g.targetPos = g.minPos;
+    if (g.currentPos <= g.minPos && absf(g.velocity) < 1.0f) {
+      g.sweepTowardMax = true;
+      g.targetPos = g.maxPos;
+    }
+  }
+}
+
+void updateGauge(uint8_t id) {
+  Gauge& g = gauges[id];
+
+  if (g.homingState != HS_IDLE) {
+    updateHoming(id);
+    return;
+  }
+
+  if (!g.homed) return;
+
+  if (g.sweepEnabled) {
+    updateSweepTarget(id);
+  }
+
+  unsigned long now = micros();
+  if (g.lastUpdateMicros == 0) {
+    g.lastUpdateMicros = now;
+    return;
+  }
+
+  float dt = (now - g.lastUpdateMicros) / 1000000.0f;
+  g.lastUpdateMicros = now;
+
+  if (dt <= 0.0f || dt > 0.1f) return;
+
+  long error = g.targetPos - g.currentPos;
+
+  if (error == 0 && absf(g.velocity) < 0.01f) {
+    g.velocity = 0.0f;
+    g.stepAccumulator = 0.0f;
+    return;
+  }
+
+  float dir = (error > 0) ? 1.0f : (error < 0 ? -1.0f : 0.0f);
+  float brakingDistance = (g.velocity * g.velocity) / (2.0f * g.accel + 0.0001f);
+
+  if ((float)labs(error) <= brakingDistance) {
+    if (g.velocity > 0.0f) {
+      g.velocity -= g.accel * dt;
+      if (g.velocity < 0.0f) g.velocity = 0.0f;
+    } else if (g.velocity < 0.0f) {
+      g.velocity += g.accel * dt;
+      if (g.velocity > 0.0f) g.velocity = 0.0f;
+    }
+  } else {
+    g.velocity += dir * g.accel * dt;
+    if (g.velocity > g.maxSpeed) g.velocity = g.maxSpeed;
+    if (g.velocity < -g.maxSpeed) g.velocity = -g.maxSpeed;
+  }
+
+  if (fabs(g.velocity) < 0.01f && error != 0) {
+    g.velocity = dir * 5.0f;
+  }
+
+  g.stepAccumulator += g.velocity * dt;
+
+  while (g.stepAccumulator >= 1.0f) {
+    if (g.currentPos == g.targetPos) {
+      g.stepAccumulator = 0.0f;
+      g.velocity = 0.0f;
+      break;
+    }
+
+    doStep(id, +1, false);
+    g.stepAccumulator -= 1.0f;
+
+    if (g.currentPos >= g.maxPos) {
+      g.currentPos = g.maxPos;
+      g.targetPos = g.maxPos;
+      g.velocity = 0.0f;
+      g.stepAccumulator = 0.0f;
+      break;
+    }
+  }
+
+  while (g.stepAccumulator <= -1.0f) {
+    if (g.currentPos == g.targetPos) {
+      g.stepAccumulator = 0.0f;
+      g.velocity = 0.0f;
+      break;
+    }
+
+    doStep(id, -1, false);
+    g.stepAccumulator += 1.0f;
+
+    if (g.currentPos <= g.minPos) {
+      g.currentPos = g.minPos;
+      g.targetPos = g.minPos;
+      g.velocity = 0.0f;
+      g.stepAccumulator = 0.0f;
+      break;
+    }
+  }
+}
+
+bool parseSet(const String& line) {
+  int id;
+  long pos;
+  if (sscanf(line.c_str(), "SET %d %ld", &id, &pos) == 2) {
+    if (id < 0 || id >= GAUGE_COUNT) {
+      sendReply("ERR BAD_ID");
+      return true;
+    }
+
+    Gauge& g = gauges[id];
+    pos = constrain(pos, g.minPos, g.maxPos);
+    g.targetPos = pos;
+    g.sweepEnabled = false;
+    sendReply("OK");
+    return true;
+  }
+  return false;
+}
+
+bool parseSpeed(const String& line) {
+  int firstSpace = line.indexOf(' ');
+  int secondSpace = line.indexOf(' ', firstSpace + 1);
+  if (firstSpace < 0 || secondSpace < 0) return false;
+  if (line.substring(0, firstSpace) != "SPEED") return false;
+
+  int id = line.substring(firstSpace + 1, secondSpace).toInt();
+  float speed = line.substring(secondSpace + 1).toFloat();
+
+  if (id < 0 || id >= GAUGE_COUNT) {
+    sendReply("ERR BAD_ID");
+    return true;
+  }
+  if (speed <= 0.0f) {
+    sendReply("ERR BAD_SPEED");
+    return true;
+  }
+
+  gauges[id].maxSpeed = speed;
+  sendReply("OK");
+  return true;
+}
+
+bool parseAccel(const String& line) {
+  int firstSpace = line.indexOf(' ');
+  int secondSpace = line.indexOf(' ', firstSpace + 1);
+  if (firstSpace < 0 || secondSpace < 0) return false;
+  if (line.substring(0, firstSpace) != "ACCEL") return false;
+
+  int id = line.substring(firstSpace + 1, secondSpace).toInt();
+  float accel = line.substring(secondSpace + 1).toFloat();
+
+  if (id < 0 || id >= GAUGE_COUNT) {
+    sendReply("ERR BAD_ID");
+    return true;
+  }
+  if (accel <= 0.0f) {
+    sendReply("ERR BAD_ACCEL");
+    return true;
+  }
+
+  gauges[id].accel = accel;
+  sendReply("OK");
+  return true;
+}
+
+bool parseEnable(const String& line) {
+  int id, en;
+  if (sscanf(line.c_str(), "ENABLE %d %d", &id, &en) == 2) {
+    if (id < 0 || id >= GAUGE_COUNT) {
+      sendReply("ERR BAD_ID");
+      return true;
+    }
+
+    setEnable(id, en != 0);
+    sendReply("OK");
+    return true;
+  }
+  return false;
+}
+
+bool parseZero(const String& line) {
+  int id;
+  if (sscanf(line.c_str(), "ZERO %d", &id) == 1) {
+    if (id < 0 || id >= GAUGE_COUNT) {
+      sendReply("ERR BAD_ID");
+      return true;
+    }
+
+    Gauge& g = gauges[id];
+    g.currentPos = 0;
+    g.targetPos = 0;
+    g.velocity = 0.0f;
+    g.stepAccumulator = 0.0f;
+    g.homed = true;
+    g.sweepEnabled = false;
+    sendReply("OK");
+    return true;
+  }
+  return false;
+}
+
+bool parseHome(const String& line) {
+  int id;
+  if (sscanf(line.c_str(), "HOME %d", &id) == 1) {
+    if (id < 0 || id >= GAUGE_COUNT) {
+      sendReply("ERR BAD_ID");
+      return true;
+    }
+
+    requestHome(id);
+    sendReply("OK");
+    return true;
+  }
+
+  if (line == "HOMEALL") {
+    requestHomeAll();
+    sendReply("OK");
+    return true;
+  }
+
+  return false;
+}
+
+bool parseSweep(const String& line) {
+  int firstSpace = line.indexOf(' ');
+  int secondSpace = line.indexOf(' ', firstSpace + 1);
+  int thirdSpace = line.indexOf(' ', secondSpace + 1);
+
+  if (firstSpace < 0 || secondSpace < 0 || thirdSpace < 0) return false;
+  if (line.substring(0, firstSpace) != "SWEEP") return false;
+
+  int id = line.substring(firstSpace + 1, secondSpace).toInt();
+  float accel = line.substring(secondSpace + 1, thirdSpace).toFloat();
+  float speed = line.substring(thirdSpace + 1).toFloat();
+
+  if (id < 0 || id >= GAUGE_COUNT) {
+    sendReply("ERR BAD_ID");
+    return true;
+  }
+
+  Gauge& g = gauges[id];
+
+  if (accel <= 0.0f || speed <= 0.0f) {
+    g.sweepEnabled = false;
+    g.velocity = 0.0f;
+    g.stepAccumulator = 0.0f;
+    sendReply("OK");
+    return true;
+  }
+
+  g.accel = accel;
+  g.maxSpeed = speed;
+  g.sweepEnabled = true;
+  g.sweepTowardMax = true;
+  g.targetPos = g.maxPos;
+  sendReply("OK");
+  return true;
+}
+
+bool parsePosQuery(const String& line) {
+  if (line == "POS?") {
+    for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
+      CMD_PORT.print("POS ");
+      CMD_PORT.print(i);
+      CMD_PORT.print(' ');
+      CMD_PORT.print(gauges[i].currentPos);
+      CMD_PORT.print(' ');
+      CMD_PORT.print(gauges[i].targetPos);
+      CMD_PORT.print(' ');
+      CMD_PORT.print(gauges[i].homed ? 1 : 0);
+      CMD_PORT.print(' ');
+      CMD_PORT.print((int)gauges[i].homingState);
+      CMD_PORT.print(' ');
+      CMD_PORT.println(gauges[i].sweepEnabled ? 1 : 0);
+    }
+    sendReply("OK");
+    return true;
+  }
+  return false;
+}
+
+bool parsePing(const String& line) {
+  if (line == "PING") {
+    sendReply("PONG");
+    return true;
+  }
+  return false;
+}
+
+bool parseLedQuery(const String& line) {
+  if (line == "LED?") {
+    for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
+      for (uint8_t j = 0; j < gaugePins[i].ledCount; j++) {
+        const CRGB& c = leds[gaugeLedOffset[i] + j];
+        CMD_PORT.print("LED ");
+        CMD_PORT.print(i);
+        CMD_PORT.print(' ');
+        CMD_PORT.print(j);
+        CMD_PORT.print(' ');
+        CMD_PORT.print(c.r);
+        CMD_PORT.print(' ');
+        CMD_PORT.print(c.g);
+        CMD_PORT.print(' ');
+        CMD_PORT.println(c.b);
+      }
+    }
+    sendReply("OK");
+    return true;
+  }
+  return false;
+}
+
+bool parseLed(const String& line) {
+  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; }
+    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;
+  }
+  return false;
+}
+
+void processLine(const String& line) {
+  if (parseSet(line)) return;
+  if (parseSpeed(line)) return;
+  if (parseAccel(line)) return;
+  if (parseEnable(line)) return;
+  if (parseZero(line)) return;
+  if (parseHome(line)) return;
+  if (parseSweep(line)) return;
+  if (parsePosQuery(line)) return;
+  if (parseLedQuery(line)) return;
+  if (parseLed(line)) return;
+  if (parsePing(line)) return;
+
+  sendReply("ERR BAD_CMD");
+}
+
+void readCommands() {
+  while (CMD_PORT.available()) {
+    char c = (char)CMD_PORT.read();
+
+    if (c == '\n') {
+      rxLine.trim();
+      if (rxLine.length() > 0) {
+        processLine(rxLine);
+      }
+      rxLine = "";
+    } else if (c != '\r') {
+      rxLine += c;
+      if (rxLine.length() > 120) {
+        rxLine = "";
+        sendReply("ERR TOO_LONG");
+      }
+    }
+  }
+}
+
+void setup() {
+  DEBUG_PORT.begin(115200);
+  DEBUG_PORT.println("Gauge controller booting");
+
+  for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
+    pinMode(gaugePins[i].dirPin, OUTPUT);
+    pinMode(gaugePins[i].stepPin, OUTPUT);
+
+    digitalWrite(gaugePins[i].dirPin, LOW);
+    digitalWrite(gaugePins[i].stepPin, gaugePins[i].stepActiveHigh ? LOW : HIGH);
+
+    if (gaugePins[i].enablePin >= 0) {
+      pinMode(gaugePins[i].enablePin, OUTPUT);
+      setEnable(i, true);
+    }
+
+    gauges[i].lastUpdateMicros = micros();
+  }
+
+  // Compute per-gauge LED offsets and initialise the strip.
+  uint8_t ledOff = 0;
+  for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
+    gaugeLedOffset[i] = ledOff;
+    ledOff += gaugePins[i].ledCount;
+  }
+  FastLED.addLeds<WS2812B, LED_DATA_PIN, GRB>(leds, TOTAL_LEDS);
+  FastLED.setBrightness(255);
+  FastLED.show();
+
+  requestHomeAll();
+
+  DEBUG_PORT.println("READY");
+  sendReply("READY");
+}
+
+void loop() {
+  readCommands();
+
+  for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
+    updateGauge(i);
+  }
+}