HS401x Datasheet

R36DS0023EU0103 Rev.1.03

Jun 6, 2022

Page 13

4.4.4.

Measurement Conversion Times

The HS401x series sensors are designed to have relatively fast conversion times. The conversion time depends

on the resolution of the measurement and the command type (temperature or humidity and temperature). Table

6 summarizes the conversion times for different resolutions.

Table 6. Conversion Times

Measurement

Resolution(bits)

Measurement Time (ms)

Temperature

8

0.37

10

0.45

12

0.60

14

0.91

Humidity and Temperature [1]

8

0.64

10

0.80

12

1.04

14

1.70

1.

Assuming the same resolution settings for both humidity and temperature measurements.

4.4.5.

CRC Checksum Calculation

An 8-bit CRC checksum is transmitted after each measurement so the user can check for data corruption during

communications if desired. The properties of the CRC algorithm used are summarized in Table 7, and the CRC

is based on all 4 bytes of measurement data (2 bytes of humidity data followed by 2 bytes of temperature data).

For temperature-only measurements, the 2 bytes of humidity data are set to be all 0’s for the CRC calculation.

Table 7. CRC Checksum Properties

Property

Value

Input Data Width

32 bits

CRC Width

8 bits

Polynomial

Initial Value

0xFF

Final XOR Value

0x00

Reflect Input

No

Reflect Output

No

Example

CRC (0x05800580) = 0xF2

4.5

Periodic Measurement Mode

The HS401x sensors can also be configured to measure at regular intervals without user intervention, and the

process to enable this mode is described in section 4.8.2. In this mode, the user can read the latest relative

humidity / temperature data by issuing a data fetch sequence, which consists of sending the HS401x I2C

sequence is illustrated in Figure 16.