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3 Digital Interface Description

All SCD4x commands and data are mapped to a 16-bit address space.

SCD4x

Hex. Code

0x62

3.1 Power-Up and Communication Start

voltage, the sensor needs 1000 ms to enter the idle state. Once the idle state is entered it is ready to receive commands from

the master.

bus specification.

3.2 Data type & length

Data sent to and received from the sensor consists of a sequence of 16-bit commands and/or 16-bit words (each to be interpreted

as unsigned integer, most significant byte transmitted first). Each data word is immediately succeeded by an 8-bit CRC. In write

direction it is mandatory to transmit the checksum. In read direction it is up to the master to decide if it wants to process the

checksum (see chapter 3.11).

3.3 Command Sequence Types

sequence types is built-up.

Figure 2: Command Sequence types: “write” sequence, “send command” sequence, “read”

sequence, and “send command and fetch result” sequence.

For “read”” or “send command and fetch results” sequences, after writing the address and/or data to the sensor and sending the

required to wait the command execution time before issuing the read header. Commands must not be sent while a previous

command is being processed.