# Construct ESP32 Firmware

Peripheral firmware for ESP32 — speaks the same JSON-over-serial protocol as the STM32 firmware. Flash this to your ESP32, then configure Construct on the host to connect via serial.

**New to this?** See [SETUP.md](SETUP.md) for step-by-step commands and troubleshooting.

## Protocol


- **Request** (host → ESP32): `{"id":"1","cmd":"gpio_write","args":{"pin":13,"value":1}}\n`
- **Response** (ESP32 → host): `{"id":"1","ok":true,"result":"done"}\n`

Commands: `gpio_read`, `gpio_write`.

## Prerequisites

1. **RISC-V ESP-IDF** (ESP32-C2/C3): Uses nightly Rust with `build-std`.

   **Python**: ESP-IDF requires Python 3.10–3.13 (not 3.14). If you have Python 3.14:
   ```sh
   brew install python@3.12
   ```

   **virtualenv** (needed by ESP-IDF tools; PEP 668 workaround on macOS):
   ```sh
   /opt/homebrew/opt/python@3.12/bin/python3.12 -m pip install virtualenv --break-system-packages
   ```

   **Rust tools**:
   ```sh
   cargo install espflash ldproxy
   ```

   The project's `rust-toolchain.toml` pins nightly + rust-src. `esp-idf-sys` downloads ESP-IDF automatically on first build. Use Python 3.12 for the build:
   ```sh
   export PATH="/opt/homebrew/opt/python@3.12/libexec/bin:$PATH"
   ```

2. **Xtensa targets** (ESP32, ESP32-S2, ESP32-S3): Use espup instead:
   ```sh
   cargo install espup espflash
   espup install
   source ~/export-esp.sh
   ```
   Then edit `.cargo/config.toml` to change the target (e.g. `xtensa-esp32-espidf`).

## Build & Flash

```sh
cd firmware/esp32
# Use Python 3.12 (required if you have 3.14)
export PATH="/opt/homebrew/opt/python@3.12/libexec/bin:$PATH"
# Optional: pin MCU (esp32c3 or esp32c2)
export MCU=esp32c3
cargo build --release
espflash flash target/riscv32imc-esp-espidf/release/esp32 --monitor
```

## Host Config

Add to `config.toml`:

```toml
[peripherals]
enabled = true

[[peripherals.boards]]
board = "esp32"
transport = "serial"
path = "/dev/ttyUSB0"   # or /dev/ttyACM0, COM3, etc.
baud = 115200
```

## Pin Mapping

Default GPIO 2 and 13 are configured for output. Edit `src/main.rs` to add more pins or change for your board. ESP32-C3 has different pin layout — adjust UART pins (gpio21/gpio20) if needed.

## Edge-Native (Future)

Phase 6 also envisions Construct running *on* the ESP32 (WiFi + LLM). This firmware is the host-mediated serial peripheral; edge-native will be a separate crate.
