Sensirion SHT31 temperature & humidity I2C to the cloud with an ESP32
A factory-calibrated digital temperature and humidity sensor with better accuracy than the DHT family, read by the gateway's built-in SHT31 driver. Temperature in °C and relative humidity in %.
The Synacl ESP32 gateway reads the Sensirion SHT31 temperature & humidity over I²C. This catalog entry carries the register map, scaling and connection defaults below, so adding it in the app is a pick from a list rather than a form filled in from the datasheet — and it is the same data an AI agent gets from the list_catalog MCP tool.
Registers · 2 tags
| Tag | Unit | I²C address | Scale |
|---|---|---|---|
Temperaturetemperature_ambient | °C | 0x44 | × 1 |
Relative humidityhumidity_relative | % | 0x44 | × 1 |
Engineering value = raw × scale + offset; the gateway sends the raw reading and Synacl scales it.
Connection defaults
| I²C address | 0x44 |
|---|---|
| Sensor driver | SHT31 |
| Bus pins (gateway default) | SDA GPIO 21 · SCL GPIO 22 (3.3 V) |
| Bus clock | 100 kHz |
Wiring
I²C: SDA to GPIO 21, SCL to GPIO 22 (the gateway defaults), VCC to 3.3 V, GND to GND. Leave the ADDR pin low (or unconnected on most breakouts) for address 0x44.
Notes
- Default address 0x44 (68). ADDR tied high moves it to 0x45 (69) — change i2cAddress on both tags.
- The built-in driver matches tags by name prefix: temperature_* and humidity_*. Keep those keys.
- Datasheet-derived (the driver is Adafruit's SHT31 library on the gateway); not yet bench-verified on this platform. If a reading does not match, report the mismatch.
Set it up in three steps
- Flash the gateway from the browser
Plug an ESP32 dev board into USB, open the free web flasher in Chrome or Edge and write the Synacl gateway firmware. It asks for Wi-Fi and pairs the gateway with your account — nothing to install, about two minutes. - Add the Sensirion SHT31 temperature & humidity from the catalog
In the app open Devices → Add device and choose “Start from a catalog device”, then pick Sensirion SHT31 temperature & humidity. The I²C settings and every tag in the table above are filled in; choose the gateway it is wired to, change the I²C address if yours differs, and save. How the catalog picker works → - Watch the live data arrive
The gateway receives the new configuration over MQTT within seconds and starts polling. Readings show on the device page and in any dashboard widget you bind to them; add a rule for alerts, keep history for reports, or let an AI agent read it over MCP.
How this entry was verified
Datasheet-derived — derived from the vendor datasheet and not yet confirmed on hardware — please report a mismatch.
Bench-verified means Synacl ran this entry on real hardware. Datasheet-derived means the map was transcribed from the vendor's documentation, so a register may be off by one or in the other word order on your unit — a two-line email fixes it for everyone.
Report a register mismatch · Vendor datasheet ↗ · All catalog devices
Try it on your own hardware
Synacl is free for five devices — no card, no sales call. Flash a gateway from the browser, add the Sensirion SHT31 temperature & humidity from the catalog, and see live data in a few minutes.