# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Build & Upload

Main firmware lives in `Gaugecontroller/Gaugecontroller.ino`. No external libraries required on the `Stepper-Only` branch. Use the Arduino IDE or `arduino-cli`:

The ESP32 bridge runs ESPHome; the config is in `gaugecontroller.yaml`.

```bash
# Compile (replace board/port as needed)
arduino-cli compile --fqbn arduino:avr:mega Gaugecontroller

# Upload
arduino-cli upload -p /dev/ttyACM0 --fqbn arduino:avr:mega Gaugecontroller
```

Current default serial setup: `CMD_PORT` and `DEBUG_PORT` both point to `Serial` (USB) at 38400 baud.

## 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   Serial1  // command channel (host sends SET, HOME, etc.)
#define DEBUG_PORT Serial1  // diagnostic prints (homing, boot messages)
```

**Current default:** both point to `Serial` (USB), so command and debug traffic go over the Arduino USB port at 38400 baud.

**USB-only debug setup:** point both defines back at `Serial` if you want to talk to the sketch over the Arduino USB port instead:

```cpp
#define CMD_PORT   Serial
#define DEBUG_PORT Serial
```

At that point the matching `begin()` call in `setup()` also needs to use the same baud rate you expect on the host side.

**Split command/debug ports:** if `CMD_PORT` and `DEBUG_PORT` do not point to the same serial port, `setup()` must initialise both. Right now it only calls:

```cpp
DEBUG_PORT.begin(38400);
```

If you split them, add a second `CMD_PORT.begin(...)` call.

Arduino Mega hardware UARTs for reference:

| Port    | TX pin | RX pin |
|---------|--------|--------|
| Serial1 | 18     | 19     |
| Serial2 | 16     | 17     |
| Serial3 | 14     | 15     |

## Architecture

The sketch controls `GAUGE_COUNT` stepper-motor gauges using a trapezoidal velocity profile and a simple text serial protocol.

### Key data structures

- `GaugeConfig` — compile-time config per gauge: pin assignments (dir, step, enable, polarity flags) and motion defaults (minPos, maxPos, homingBackoffSteps, maxSpeed, accel, homingSpeed). All gauges are defined in `gauge_config.h` as `constexpr GaugeConfig gaugeConfigs[]`. `GAUGE_COUNT` is derived automatically from the array length.
- `Gauge` — per-gauge runtime state: position, target, velocity, accel, homing state machine, sweep mode. Initialised from `gaugeConfigs[]` in `setup()`.

### 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.

### 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>` |
| `CFG?` | `CFG?` | Query all gauges: `CFG <id> <maxSpeed> <accel>` per gauge |
| `PING` | `PING` | Responds `PONG` |

All commands reply `OK` or `ERR BAD_ID` / `ERR BAD_CMD` etc.

### Adding gauges

1. Open `Gaugecontroller/gauge_config.h` and append one row to `gaugeConfigs[]`.
2. `GAUGE_COUNT` updates automatically — no other changes needed.