This is an Arduino library for Aosong ASAIR AHT10/AHT15/AHT20/AHT21/AHT25/AM2301B/AM2311B Digital Humidity & Temperature Sensor

• AHT1x +1.8v..+3.6v, AHT2x +2.2v..+5.5v
• AHT1x 0.25μA..320μA, AHT2x 0.25μA..980μA
• temperature range -40°C..+85°C
• humidity range 0%..100%
• typical accuracy T ±0.3°C, RH ±2% (1)
• typical resolution T 0.01°C, RH 0.024%
• normal operating range T -20°C..+60°C, RH 10%..80%
• maximum operating rage T -40°C..+80°C, RH 0%..100%
• I²C bus speed 100KHz..400KHz, 10KHz recommended minimum
• recommended measurement frequency 8sec..30sec (2)
• recommended to route VDD or GND between I²C lines to reduce crosstalk between SCL & SDA
• power supply pins must be decoupled with 100nF capacitor

Supports all sensors features:

• read humidity (3)
• read temperature (3)
• soft reset with sensor initialization
• CRC calculation for AHT2x (3)

Tested on:

• Arduino AVR
• Arduino ESP8266
• Arduino ESP32
• Arduino STM32
• Arduino SAMD21

(1) Prolonged exposure for 60 hours at humidity > 80% can lead to a temporary drift of the signal +3%. Sensor slowly returns to the calibrated state at normal operating conditions.
(2) High frequency measurement causes the sensor to heat up, the interval must be greater than 1 second to keep self-heating below 0.1°C.
(3) Library returns 255 if a communication error occurs, calibration coefficient is off or CRC doesn't match (for AHT2x only).