ATH25 Data Sheet

www.aosong.com

Version:V1.0 —— May 2021

11 / 14

continue to wait.

4.After receiving six bytes, the next byte is the CRC check data. The user can read it out as

needed. If the receiving end needs CRC check, an ACK will be sent after the sixth byte is

received. Reply, otherwise send NACK to end, the initial value of CRC is 0XFF, and the CRC8

check polynomial is:

CRC [7:0] = 1+X4+X5+X8

5.Calculate the temperature and humidity value

Note: The calibration status check in the first step only needs to be checked when the power is

turned on. No operation is required during the acquisition process.

Trigger measurement data

Read temperature and humidity data

Note: The sensor needs time to collect. After the host sends a measurement command (0xAC), delay

more than 80 milliseconds before reading the converted data and judging whether the returned status bit

is normal. If the status bit [Bit7] is 0, it means that the data can be read normally. When it is 1, the

sensor is busy, and the host needs to wait for the data processing to complete.

8 Signal Conversion

8.1 Relative Humidity Conversion

The relative humidity RH can be calculated according to the relative humidity signal SRH output

by SDA through the following formula (the result is expressed in %RH):

%

100

*

)

2

S

(

[%]

RH

20

RH

