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5.4 I2C Command Overview

Command

(hex)

Response length

incl. CRC (bytes)

Description

[return values]

0xFD

6

measure T & RH with high precision (high repeatability)

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0xF6

6

measure T & RH with medium precision (medium repeatability)

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0xE0

6

measure T & RH with lowest precision (low repeatability)

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0x89

6

read serial number

[2 * 8-bit data; 8-bit CRC; 2 * 8-bit data; 8-bit CRC]

0x94

-

soft reset

[ACK]

0x39

6

activate heater with 200mW for 1s, including a high precision

measurement just before deactivation

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0x32

6

activate heater with 200mW for 0.1s including a high precision

measurement just before deactivation

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0x2F

6

activate heater with 110mW for 1s including a high precision

measurement just before deactivation

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0x24

6

activate heater with 110mW for 0.1s including a high precision

measurement just before deactivation

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0x1E

6

activate heater with 20mW for 1s including a high precision

measurement just before deactivation

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0x15

6

activate heater with 20mW for 0.1s including a high precision

measurement just before deactivation

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

Table 9. Overview of I2C commands. If the sensor is not ready to process a command, e.g. because it is still

measuring, it will return NACK to the I2C read header. Given heater power values are typical and valid for

VDD = 5 V. At VDD = 3.3 V, heating power is reduced to 5% of the nominal value.

5.5 Conversion of Signal Output

The digital sensor signals correspond to following humidity and temperature values:

������������ = (−6 + 125 ∙

������������������

216 − 1

) %������������

1

������ = (−45 + 175 ∙

������������

216 − 1

) °C

2

������ = (−49 + 315 ∙

������������

216 − 1

) °F

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