avsa242 / scd4x-spin

Parallax P8X32A/Propeller, P2X8C4M64P/Propeller 2 driver object for the Sensirion SCD4x CO2 sensors

scd4x-spin

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This is a P8X32A/Propeller, P2X8C4M64P/Propeller 2 driver object for the Sensirion SCD-4x CO2 sensors

IMPORTANT: This software is meant to be used with the spin-standard-library (P8X32A) or p2-spin-standard-library (P2X8C4M64P). Please install the applicable library first before attempting to use this code, otherwise you will be missing several files required to build the project.

Salient Features

• SCD-40, SCD-41 supported
• I2C connection at up to 100kHz
• Read serial number
• Read CO2 concentration, temperature, RH
• Set compensation for local altitude above sea level, or ambient pressure
• Automatic or manual CO2 calibration
• Set temperature bias/offset
• Continuous (SCD40, SCD41), continuous low-power (SCD40, SCD41) or single-shot (SCD41 only) measurement modes
• Power down sensor (SCD41 only)
• Save configuration settings to sensor EEPROM
• Sensor built-in self-test

Requirements

P1/SPIN1:

• spin-standard-library
• 1 extra core/cog for the PASM I2C engine (none if the SPIN I2C engine is used)
• sensor.temp.common.spinh (source: spin-standard-library)
• sensor.rh.common.spinh (source: spin-standard-library)
• sensor.co2.common.spinh (source: spin-standard-library)

P2/SPIN2:

• p2-spin-standard-library
• sensor.temp.common.spin2h (source: p2-spin-standard-library)
• sensor.rh.common.spin2h (source: p2-spin-standard-library)
• sensor.co2.common.spin2h (source: p2-spin-standard-library)

Compiler Compatibility

Processor	Language	Compiler	Backend	Status
P1	SPIN1	FlexSpin (6.2.1)	Bytecode	OK
P1	SPIN1	FlexSpin (6.2.1)	Native/PASM	OK
P2	SPIN2	FlexSpin (6.2.1)	NuCode	FTBFS
P2	SPIN2	FlexSpin (6.2.1)	Native/PASM2	OK

(other versions or toolchains not listed are not supported, and may or may not work)

Hardware compatibility

• Tested with Adafruit SCD40
• Tested with Adafruit SCD41

Limitations

• Very early in development - may malfunction, or outright fail to build
• Range of allowed values for ambient pressure compensation isn't verified (not available in datasheet), so it was copied from the SCD30

scd4x-spin's Issues

co2, temp, rh methods only return data when DRDY is low

The original intent was to return cached data if the data ready signal was low (i.e., not ready) and live data otherwise.
However, they way they're currently written, data only gets returned if the data ready signal is low. They should always return data, otherwise whatever the (uninitialized) return vars contained would be returned (most likely 0).