An ESP32-S3-based environmental sensor node that monitors temperature, humidity, TVOC, and eCO2, broadcasting readings over a CAN bus. Supports over-the-air (OTA) firmware updates and WiFi credential provisioning via CAN.
- MCU: Waveshare ESP32-S3-Zero (CPU clocked at 80 MHz for reduced power consumption)
- Temperature/Humidity: SHT31-D sensor (I2C)
- Air Quality: SGP30 TVOC and eCO2 sensor (I2C)
- CAN Transceiver: SN65HVD230DR (3.3V, 500 kbps)
- Status LED: Onboard WS2812 RGB LED (GPIO 21)
| Pin | GPIO | Function |
|---|---|---|
| 8 | GPIO5 | I2C SCL (SGP30, SHT31-D) |
| 9 | GPIO6 | I2C SDA (SGP30, SHT31-D) |
| 12 | GPIO9 | CAN TX |
| 13 | GPIO10 | CAN RX |
| - | GPIO21 | Onboard RGB LED |
- KiCad schematic and PCB files are in the
EDA/directory
This project uses PlatformIO.
# Build
pio run
# Upload via USB
pio run --target upload
# Monitor serial output
pio device monitorAll communication uses a 500 kbps CAN bus. The device transmits sensor data and receives OTA/WiFi configuration commands.
CAN ID: 0x1F | DLC: 8
| Byte | Content |
|---|---|
| 0 | Temperature (C, rounded integer) |
| 1 | Temperature (F, rounded integer) |
| 2-3 | Humidity (big-endian, value x 100) |
| 4-5 | TVOC in ppb (big-endian) |
| 6-7 | eCO2 in ppm (big-endian) |
Sensor data is transmitted every 2 seconds when both SHT31-D and SGP30 readings are valid. The SGP30 receives humidity compensation from the SHT31-D for improved accuracy.
CAN ID: 0x00 | DLC: 3+
Send the last 3 bytes of the target device's MAC address to trigger OTA mode on that specific device.
| Byte | Content |
|---|---|
| 0-2 | Target MAC bytes (e.g., F2 7E 6C for hostname esp32-F27E6C) |
When triggered, the device connects to its configured WiFi network and listens for ArduinoOTA uploads for 3 minutes before returning to normal operation.
CAN ID: 0x01 | DLC: varies
WiFi credentials are provisioned over CAN using a chunked protocol. Credentials are stored in NVS (non-volatile storage) and persist across reboots.
| Byte 0 | Message Type |
|---|---|
0x01 |
Start: contains SSID length, password length, chunk counts |
0x02 |
SSID chunk: 6-byte payload with chunk index |
0x03 |
Password chunk: 6-byte payload with chunk index |
0x04 |
End: contains XOR checksum for validation |
The protocol includes a 5-second timeout — if chunks stop arriving, the state resets.
The onboard RGB LED indicates the device state:
| Color | State |
|---|---|
| Green | Normal operation |
| Blue | OTA update mode (waiting for firmware upload) |
- Provision WiFi credentials via CAN (one-time setup, stored in NVS)
- Send an OTA trigger message on CAN ID
0x00with the target device's MAC suffix - The LED turns blue and the device connects to WiFi
- Upload firmware using ArduinoOTA within the 3-minute window
- On success, the device reboots with new firmware and the LED returns to green
- On timeout, the device disconnects WiFi and resumes normal operation
The device hostname is printed to serial at boot (format: esp32-XXYYZZ).
| Range (ppb) | Rating |
|---|---|
| < 65 | Excellent |
| 65-219 | Good |
| 220-659 | Moderate |
| 660-2199 | Poor |
| >= 2200 | Unhealthy |
| Range (ppm) | Level |
|---|---|
| < 400 | Low (fresh air) |
| 400-999 | Normal |
| 1000-1999 | High |
| >= 2000 | Alarm |
| Library | Source |
|---|---|
| ESP32ArduinoDebugLibrary | TrailCurrent |
| TwaiTaskBasedLibrary | TrailCurrent |
| OtaUpdateLibrary | TrailCurrent |
| Adafruit SHT31 Library | Adafruit |
| Adafruit SGP30 Sensor | Adafruit |