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AHT20 Data Sheet

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The abbreviations are explained in Table 8. The thicker SDA line is controlled by the sensor, and the ordinary SDA

line is controlled by the single-chip microcomputer. Please note that the SDA valid read time is triggered by the

falling edge of the previous conversion.

Table 8. Timing characteristics of I²C fast mode digital Inputs/outputs.

The meaning is shown in Figure 17 Unless otherwise noted.

7 Sensor Communication

Sensor uses standard I²C protocol for communication. For information about the I²C protocol other than the

following chapters, please refer to the following website: www.aosong.com provides a sample program for

reference.

7.1 Start the Sensor

The first step is to power up the sensor with the selected VDD supply voltage (range between 2.2V and 5.5V).

After power-on, the sensor needs ≥100ms time (SCL is high at this time) to reach the idle state and it is ready to

receive commands sent by the host (MCU).

7.2 Start/Stop Sequence

Each transmission sequence starts with the Start state and ends with the Stop state, as shown in Figure 18 and

Figure 19.

Figure 18. Start transmission status (S)

When SCL is high, SDA is converted from high to low. The start state is a special bus state controlled by the

master, indicating the start of the slave transfer (after Start, the BUS bus is generally considered to be in a busy

state)

Figure 19. Stop transmission state (P)