Hannes
ac5a556c11
- firmware/: config + secrets templates committed, flashed config git-ignored - README: document the GND pour on F.Cu/B.Cu and the module keep-out rule areas - README: correct the calibration button wiring (S8 bCal_in, not an MCU GPIO) - README: v2 list - dedicated 5 V power input, decoupling, mounting holes, I2C pull-ups, schematic annotation, RoHS finish, project name, antenna keep-out
Firmware
ESPHome firmware for the ESP32-C3 CO₂ & environment sensor board.
Files
| File | In git | Purpose |
|---|---|---|
esp-sensair.yaml.example |
yes | configuration template, all credentials as !secret references |
secrets.yaml.example |
yes | secrets template with placeholders |
esp-sensair.yaml |
no (git-ignored) | your flashed configuration |
secrets.yaml |
no (git-ignored) | your Wi-Fi, API, OTA and hotspot credentials |
Setup:
cp firmware/esp-sensair.yaml.example firmware/esp-sensair.yaml
cp firmware/secrets.yaml.example firmware/secrets.yaml
# fill in firmware/secrets.yaml
esphome run firmware/esp-sensair.yaml
Generate the Home Assistant API encryption key with:
python3 -c "import base64,os; print(base64.b64encode(os.urandom(32)).decode())"
Target
| Item | Value |
|---|---|
| Chip | ESP32-C3 (RISC-V, single core, Wi-Fi) |
| ESPHome board | esp32-c3-devkitm-1 |
| Framework | ESP-IDF |
| Flashing | USB-C on the devkit module (ESPHome OTA after first flash) |
Peripherals
| Peripheral | Bus | Pins | Notes |
|---|---|---|---|
| Sensirion S8 (NDIR CO₂) | UART, 9600 baud 8N1 | TX = GPIO21, RX = GPIO20 |
5 V supply, ~30 s preheat; the S8's own bCal_in pin carries the on-board calibration button |
| BME280 (T / RH / P) | I²C, address 0x76 |
SDA = GPIO7, SCL = GPIO8 |
powered from the module's 3.3 V output, pull-ups on the breakout |
| SW1 | — | not on the MCU | wired to the S8 bCal_in input with a 1 kΩ / 100 nF RC network |
Update interval for both sensors: 60 s.
Home Assistant
Exposed as native ESPHome entities: CO₂, temperature, relative humidity, pressure. API connection is encrypted (noise protocol), OTA updates enabled, static IP with a fallback hotspot and captive portal if the Wi-Fi connection fails.
Ideas for v2
- Trigger the S8 background calibration from Home Assistant (
senseairplatform actions) in addition to the hardware button, and log the calibration events. - Automatic baseline calibration window tuned to the room's nightly CO₂ minimum.
- Report Wi-Fi signal strength and device uptime as sensors for diagnostics.