AM2321 is a temperature and humidity composite sensor that contains calibrated digital signal output, using special temperature and humidity sensor acquisition technology to ensure that products with high reliability and excellent long-term stability. Sensor comprises a capacitive wet sense original and a precision integrated temperature measurement device, and with a high-performance microprocessor connected. The product has advantages like excellent quality, fast response, anti-interference ability, Cost-effective. AM2321 communication method using a single bus. Two standard I2C communication, standard single bus interface, so the system becomes quick and easy integration, ultra-small size, low power consumption, signal transmission distance up to 20 meters, making it the best choice for all types of applications. I2C communication using standard communication sequence, the user can directly linked to the I2C bus, no additional wiring, simple to use. Two means of communication are directly output humidity, temperature and check CRC and other digital information which are temperature-compensated, users do not need to calculate the secondary digital output. They can get an accurate temperature and humidity information, two means of communication can be free to switch, the user can freely choose, easy to use, wide range of applications, products for the 4-wire connection easy.