ESP32 Sensor Data to Slack Alerts

A minimal pipeline: ESP32 + BME280 → Plexus → Slack alert. The firmware sketch ships with the plexus-c  library; this guide covers the wiring, the threshold monitor, and the Slack integration.

Hardware

Use 3.3V, not 5V. Some breakouts have an onboard regulator and tolerate 5V — most don’t, and the chip dies silently if you guess wrong.

Install

1. Arduino IDE 2.x — arduino.cc .
2. ESP32 board support — Preferences → Additional Boards Manager URLs: https://espressif.github.io/arduino-esp32/package_esp32_index.json. Then Tools → Board → Boards Manager, install “esp32” by Espressif.
3. Two libraries from Sketch → Include Library → Manage Libraries: Adafruit BME280 Library and plexus-c. If plexus-c doesn’t appear, grab the latest release zip  and Sketch → Include Library → Add .ZIP Library.

Flash

1. File → Examples → plexus-c → BME280_Dashboard.
2. Edit WIFI_SSID, WIFI_PASSWORD, PLEXUS_API_KEY (from your /dev/keys page), and SOURCE_ID = "esp32-bme280".
3. Tools → Board → ESP32 Dev Module, pick the port, upload.
4. Tools → Serial Monitor → 115200 baud — you should see T=22.3°C H=54.1% P=1013.2 hPa within ~5 seconds.

Add the alert

Register a temperature threshold monitor:

export PLEXUS_API_KEY=plx_xxx   # from your /dev/keys page
 
curl -sS -X POST https://app.plexus.company/api/monitors \
  -H "x-api-key: $PLEXUS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "source_id": "esp32-bme280",
    "metric": "temperature",
    "threshold": { "max": 35.0, "severity": "warning", "message": "BME280 above 35°C — check the room" }
  }'

Then connect Slack in the Plexus app (Integrations → Slack → Connect), pick a channel, and enable alert.triggered and alert.resolved.

Test

Press the BME280 between your fingers. ~15–20 seconds of palm contact crosses 35°C, and the Slack message lands.