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sensor.co2.md

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sensor.co2

API for Carbon Dioxide sensing device drivers

Object filename description:

sensor.co2.model.spin

model indicates the manufacturer's model number of the sensor

Base Methods

These are methods that are common to all of the above types of drivers

Method Description Param Returns
startx() Start driver using explicitly defined settings Notes 1-3 cog id+1
stop() Stop the driver n/a n/a
defaults() Set sensor factory default settings n/a n/a

Notes:

  1. For I2C-connected sensors:

    • startx(SCL_PIN, SDA_PIN, I2C_FREQ, ADDR_BITS): status
    • If no particular interface preprocessor symbol is defined when building, the driver will default to the PASM-based I2C engine.
    • For some devices, a MODEL_I2C_BC variant exists, which directs the driver to use a bytecode-based engine that while much slower, doesn't use another cog.
    • Not all devices support alternate I2C addresses.

  2. For all variants: startx() returns the launched cog number+1 of com engine used on success.

  3. For all variants: There may be a RST_PIN parameter, for specifying an optional reset pin (device-dependent). The pin is only validated in the reset() method, and is ignored if set outside the allowable range.

  4. startx() returns FALSE (0) if the driver fails to start, for these possible reasons:

    • No more cogs available
    • One or more specified I/O pins are outside allowed range
    • Bus frequency is outside allowed range
    • If supported by the device, dev_id() didn't return the expected value

  5. defaults() may simply call reset(), if sensible, as opposed to calling several other driver methods, in order to reduce memory usage.

  6. Drivers may have one or more preset_() methods, that establish a set of pre-set settings.

  7. stop() performs the following tasks:

    • Stop any extra cogs that were started (if applicable)
    • Clear all global variable space used to 0

Methods

Method Description
adc2co2() Convert ADC word to CO2 data
co2_data() CO2 data ADC word
co2_ppm() CO2 concentration

adc2co2(co2_wd)

Convert ADC word to CO2 data

  • Parameters:
    • co2_wd: ADC word representing CO2 measurement
  • Returns:
    • CO2 concentration in 0.1 parts per million (e.g., 12004 is 1200.4ppm)

co2_data()

CO2 data ADC word

  • Parameters: none
  • Returns:
    • ADC word representing CO2 measurement

co2_ppm()

CO2 concentration

  • Parameters: none
  • Returns:
    • CO2 concentration in 0.1 parts per million (e.g., 12004 is 1200.4ppm)

Notes:

  1. Some devices also contain temperature and/or relative humidity sensors. These follow the sensor.temp_rh API

Build examples

Notes:

  1. Some devices require build-time features to be enabled in order to function properly. e.g., the SCD30 requires a behavioral quirk be enabled in the I2C engine, with -DQUIRK_SCD30

Build the SCD30 demo for P1, bytecode output, using the PASM-based I2C engine: flexspin --interp=rom -L$HOME/spin-standard-library/library -DQUIRK_SCD30 -DSCD30_I2C SCD30-Demo.spin

or flexspin --interp=rom -L$HOME/spin-standard-library/library -DQUIRK_SCD30 SCD30-Demo.spin

The same, but using the bytecode-based I2C engine: flexspin --interp=rom -L$HOME/spin-standard-library/library -DQUIRK_SCD30 -DSCD30_I2C_BC SCD30-Demo.spin

The same, but build using P1 native code output:

flexspin -L$HOME/spin-standard-library/library -DQUIRK_SCD30 SCD30-Demo.spin

(NOTE: An application may build successfully when using native code output and a bytecode-based engine, but may not function properly, as bus timings aren't accounted for in bytecode-based engines, so may run too fast)