- 23 -

situation.

2. 3.3V voltage supply is recommended when the cable length is not greater than 1m.

Otherwise, line drop may cause the sensor communication error.

3. The minimum interval of the read sensor 2S; reading interval is less than 2S, temperature

and humidity might result in denial or communication is unsuccessful and so on.

4. Temperature and humidity values are read out every last measurement result, want to get

real-time data, the need to continuously read twice, repeatedly suggested reading sensor, and each

sensor reading interval greater than 2 seconds to obtain accurate data.

Figure 19: AM2320 single bus typical circuit

8.3.2 Single bus communication protocol

◎ Single Bus Description

AM2321 device uses a simplified single-bus communication. Single bus that only one data line,

the data exchange system, the control by the data line is completed. Device (microprocessor) through

an open-drain or tree-state port is connected to the data line to allow the device when not

transmitting data to release the bus, and let other devices use the bus; single bus usually requires an

external 5.1kΩof approximately pull-up resistors, so that when the bus is idle, the state is high.

Because they are master-slave structure, only when the host calls the sensor, the sensor will be

answered, so the host access to the sensor must strictly follow the sequence of a single bus, if there is

a sequence of confusion, the sensor will not respond to the host.

◎Single bus transfer data definitions

SDA and AM2321 microprocessors for communication and synchronization between using single

bus data format, a 40-bit data transfer, high first-out. , The communication format specific

communication sequence shown in Figure 20 are shown in Table 9.

Figure 20: AM2321 single bus communication protocol

Table 9: AM2321 communication format

Aosong Guangzhou Electronics Co., Ltd.

Order Phone: 4006 305378

Enterprise QQ: 4006305378

www.aosong.com