Skip to content

SHT40

Sensirion SHT40 I²C temperature and humidity sensor (±0.2 °C / ±1.8 %RH class).

Live catalog

Prefer labwired_describe with the catalog id over guessing pins or addresses.

Status at a glance

Aspect Status
Catalog id sht40
Bus I²C
Address 0x44 (SHT40-AD1B); 0x45 / 0x46 for the -BD1B / -CD1B variants
Source configs/devices/sht40.yaml (declarative, no Rust model)
Datasheet Sensirion Datasheet SHT4x (v6.x): I2C command overview, conversion formulas, system timing table
Tier smoke-proven (register-level tests: crates/core/tests/everyday_sensor_set.rs)

Pins / attachment

Pin / net Role
SDA I²C SDA
SCL I²C SCL
VDD/GND Power (digital twin)

Support matrix

Behavior Status Notes
0xFD / 0xF6 / 0xE0 measure (high/med/low precision) ✅ T + RH words with CRC-8; ready after the datasheet MAX 8.3 / 4.5 / 1.6 ms, 0xFF before
0x89 serial number ✅ Constant serial, CRC-framed
0x94 soft reset ⚠️ Accepted; no state to clear
Heater commands (0x39/0x32/0x2F/0x24/0x1E/0x15) ⚠️ Take the 1.1 s / 0.11 s heater time, then measure; no heating
Repeatability noise ❌ All precisions answer the exact stimulus
Analog / power ❌ Bench

Stimulus

Host inputs: temperature (°C), humidity (%RH).

How to run

  1. Place the part and an MCU in Playground, or add it to a system YAML: 
    external_devices:
  - id: "sht40"
    type: "sht40"
    connection: "i2c0"   # the bus id your chip system uses
  2. Agent: labwired_list → labwired_describe id=sht40 → wire → labwired_validate → labwired_run / labwired_verify.
  3. Register-level smoke: cargo test -p labwired-core --test everyday_sensor_set — 0xFD → T word 0x6666 at 25 °C, RH word 0x72B0 at 50 %RH, both CRCs valid; serial 0x0F4E 0x2A71. The same file's negative control proves the check fails against a part that answers only 0x00 or only 0xFF.

Limitations

  • Single-byte opcodes, unlike the SHT3x — see sht30.yaml for that family.
  • Heater effect and repeatability noise not modelled.

See the YAML header for the full datasheet trace and every named approximation.