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Version 3.3 – November 2024

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By default, no filter is applied to the data. If smoothing is desired, the following command(s) must be executed

once upon starting the sensor. When enabled, the filter is applied for all subsequent concentration

measurements.

Please note:

•

Both filters can be activated at the same time (chained) for stronger smoothing.

•

Forced recalibration (section 3.3.7) can only benefit from this filtering if sufficient measurement points

have been taken before executing the FRC.

•

The response time (specified in section 1.1) will increase if a noise filter is applied.

•

Filtering will not function if the sensor is put to sleep between each concentration measurement, as

the last output value is lost.

3.3.10 Self-test

The self-test command runs an on-chip self-test which takes less than 30ms. It performs a full memory integrity

check and checks that the operating voltage is within specifications.

Command

Command code (hex)

Consecutive read

Description

Self-test

0x365B

Byte1: Self-test 8msb

Byte2: Self-test 8lsb

Byte3: CRC

The sensor will run an on-chip self-

test. A successful self-test will return

b00 for the two least significant bits.

The self-test errors are decoded as follows:

Bits

Error State

1:0

Memory error

9:2

For debugging only

15:10

Always 0

In case of a memory error, the sensor should be soft reset and the self-test should be repeated. If the

problem persists, the supply voltage should be cycled to trigger a Power-on-Reset and the self-test should

be repeated. If then the problem persists, measurement results might be compromised.

Bits 9:2 should only be considered during design-in and is for debugging purposes.

During design-in and debugging, the self-test should be performed during stable conditions, i.e. stable and

noise free supply voltage, and a stable pressure, humidity and temperature. If one or more bits return 1,

contact Sensirion for support.

3.3.11 Soft reset

Command

I2C address + W

bit + command

code (hex)

Consecutive

read

Description

General call reset

0x0006

NA

This sequence resets the sensor with a separate

reset block, which is as much as possible

detached from the rest of the system on chip.

Note that the I2C address is 0x00, which is the

general call address, and that the command is 8

bit. The reset is implemented according to the

I2C specification.