HTU31D RH/T SENSOR IC

Digital Relative Humidity & Temperature Sensor

REV3 01/2021

Page 8

Sensor Functions

General

Every I²C message starts with the start condition and it is ended with the stop condition. Every command consists of two bytes:

the address byte and the command byte. The sensor address is 1000’00x. The x in the address is defined with the value at the

input of the I2C_LSB pin. If I2C_LSB =0 then the address will be 1000’000 (0x40), while if the I2C_LSB = 1 then the address

will be 1000’001 (0x41). This feature allows two sensors to operate on the same I2C bus.

Command Byte

7

6

5

4

3

2

1

0

Command Name

CMD

CMD

CMD

CMD

CMD

CMD

CMD

Stop

Conversion

0

1

0

OSRRH1

OSRRH0

OSRT1

OSRT0

X

Read T & RH

0

0

0

0

0

0

0

X

Read RH

0

0

0

1

0

0

0

X

Reset

0

0

0

1

1

1

1

X

Heater on

0

0

0

0

0

1

0

X

Heater off

0

0

0

0

0

0

1

X

Read serial number

0

0

0

0

1

0

1

X

Read Diagnostic

0

0

0

0

1

0

0

X

Table 10 User Commands

Temperature & Humidity Measurement Sequence

1) Execute “Conversion” command with the desired resolution to perform measurement and load it in sensor memory

2) Wait for the conversion time (see Table 5 Timing Specifications)

3) Execute “Read T & RH” or “Read RH” command to read measurement

Note: Humidity and temperature values will be updated by the “Conversion” command.

Conversion

The conversion command triggers a single temperature and humidity conversion with Selected Resolution OSR:

Figure 5 Conversion Command

Abbreviation

Binary value

Description

osrRH1..osrRH0

11

10

01

00

Humidity OSR = 3 (0.007%RH)

Humidity OSR = 2 (0.010%RH)

Humidity OSR = 1 (0.014%RH)

Humidity OSR = 0 (0.020%RH)

osrT1..osrT0

11

10

01

00

Temperature OSR = 3 (0.012°C)

Temperature OSR = 2 (0.016°C)

Temperature OSR = 1 (0.025°C)

Temperature OSR = 0 (0.040°C)

Table 11 Humidity and Temperature Conversion Parameters and Associated Resolution