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3.4.11 perform_factory_reset

The perform_factory_reset command resets the FRC and ASC algorithm history, as well as reenables the bypass

phase (See Section 1.1.4 for more information).

Command

Command

Hex Code

Argument

Consecutive Read

Execution

Time (ms)

Description

perform_fac

tory_reset

0x3632

-

Word[0] = 0 → pass

Word[0] = 0xFFFF →

command failed

90

Resets the FRC and ASC

algorithm history.

3.4.12 perform_self_test

The perform_self_test command can be used to check the sensor functionality in an end-of-line test as well as

for design-in and debugging purposes. The self-test should be performed during stable conditions, i.e., stable

supply voltage, environmental conditions and CO2 concentration.

Command

Command

Hex Code

Argument

Consecutive Read

Execution

Time (ms)

Description

perform_self

_test

0x278C

-

Byte0: Self-test 8msb

Byte1: Self-test 8lsb

Byte2: CRC

360

Performs an on-chip self-test.

A successful test will return

either 0x0000 or 0x0010.

The self-test output is decoded as follows:

Bits

Nonzero Value

0

Supply voltage is out of specified range

3:1

For debugging purposes; contact Sensirion for support

4

SHT is not connected through STCC4 I2C controller interface pad

6:5

Memory error

In case of a memory error, the recommended operation sequence is:

1. Send the perform_soft_reset command (See Section 3.4.10) and wait for the specified execution time. Then

resend the perform_self_test command and wait for the specified execution time.

2. If the memory error persists, power cycle the supply voltage, then resend the perform_self_test command

and wait for the specified execution time.

3. If the memory error persists, measurement results may be compromised.

3.4.13 enable_testing_mode

The enable_testing_mode command is used to pause the ASC algorithm and temporarily disable updates to the

ASC state. It may be used for testing, e.g., the CO2 sensing performance during sensor qualification. The sensor

is in testing mode when the 2nd most significant bit of Byte 10 in the read_measurement command (Section

3.4.3) output is equal to 1.

Command

Command

Hex Code

Argument

Consecutive Read

Execution

Time (ms)

Description

enable_testi

ng_mode

0x3FBC

-

-

-

Enables the testing mode.