# Firmware

ESPHome configuration for the ESP32-C3 CO₂ & environment sensor board.

## Target

| Item | Value |
|---|---|
| Chip | ESP32-C3 (RISC-V, single core, Wi-Fi + BLE) |
| Framework | ESPHome (`esp32` platform, `framework: esp-idf` or `arduino`) |
| Board | this project's board, flashed via the module's UART/USB boot pins |

## Peripherals

| Peripheral | Bus | Notes |
|---|---|---|
| Sensirion S8 (NDIR CO₂) | UART, 9600 baud 8N1 | needs 5 V supply, ~30 s preheat; `bCal_in` starts a manual background calibration |
| BME280 (T / RH / P) | I²C, address `0x76` (some breakouts `0x77`) | powered from the module's 3.3 V output; pull-ups come from the breakout |
| SW1 | GPIO, active low with 1 kΩ / 100 nF RC debounce | calibration button |

## Add here

- `esp-sensair.yaml` — the ESPHome configuration actually flashed to the board
- `secrets.yaml` — **do not commit** (Wi-Fi credentials, Home Assistant token); keep
  `secrets.yaml.example` with placeholders
- flashing notes: `esptool` / `esphome flash`, boot-mode entry on the module

## Home Assistant

The device is exposed as native ESPHome entities: `co2`, `temperature`, `relative_humidity`,
`pressure`, plus the calibration button as a sensor event.