MQTT - CO2 Bricklet

This is the description of the MQTT API bindings for the CO2 Bricklet. General information and technical specifications for the CO2 Bricklet are summarized in its hardware description.

An installation guide for the MQTT API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example-simple.txt)

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# Change XYZ to the UID of your CO2 Bricklet

setup:
    # Get current CO2 concentration
    subscribe to tinkerforge/response/co2_bricklet/XYZ/get_co2_concentration
    publish '' to tinkerforge/request/co2_bricklet/XYZ/get_co2_concentration 

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your CO2 Bricklet

setup:
    # Handle incoming CO2 concentration callbacks
    subscribe to tinkerforge/callback/co2_bricklet/XYZ/co2_concentration
    publish '{"register": true}' to tinkerforge/register/co2_bricklet/XYZ/co2_concentration # Register co2_concentration callback
    
    # Set period for CO2 concentration callback to 1s (1000ms)
    # Note: The CO2 concentration callback is only called every second
    #       if the CO2 concentration has changed since the last call!
    publish '{"period": 1000}' to tinkerforge/request/co2_bricklet/XYZ/set_co2_concentration_callback_period

Threshold

Download (example-threshold.txt)

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# Change XYZ to the UID of your CO2 Bricklet

setup:
    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    publish '{"debounce": 10000}' to tinkerforge/request/co2_bricklet/XYZ/set_debounce_period
    
    # Handle incoming CO2 concentration reached callbacks
    subscribe to tinkerforge/callback/co2_bricklet/XYZ/co2_concentration_reached
    publish '{"register": true}' to tinkerforge/register/co2_bricklet/XYZ/co2_concentration_reached # Register co2_concentration_reached callback
    
    # Configure threshold for CO2 concentration "greater than 750 ppm"
    publish '{"option": "greater", "min": 750, "max": 0}' to tinkerforge/request/co2_bricklet/XYZ/set_co2_concentration_callback_threshold

API

All published payload to an from the MQTT bindings is in the JSON format.

If an error occures, the bindings publish a JSON object containing the error message as attribute "_ERROR". It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions

request/co2_bricklet/<UID>/get_co2_concentration
Response payload:
 
  • co2_concentration -- int

Returns the measured CO2 concentration. The value is in ppm (parts per million) and between 0 to 10000.

If you want to get the CO2 concentration periodically, it is recommended to use the register/co2_bricklet/<UID>/co2_concentration callback and set the period with request/co2_bricklet/<UID>/set_co2_concentration_callback_period.

Advanced Functions

request/co2_bricklet/<UID>/get_identity
Response payload:
 
  • uid -- string
  • connected_uid -- string
  • position -- string
  • hardware_version -- [int,int,int]
  • firmware_version -- [int,int,int]
  • device_identifier -- int (has symbols)
  • _display_name -- string

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here. If symbolic output is not disabled, the device identifier is mapped to the corresponding name in the format used in topics.

The display name contains the CO2's name in a human readable form.

Callback Configuration Functions

request/co2_bricklet/<UID>/set_co2_concentration_callback_period
Request payload:
 
  • period -- int

Sets the period in ms with which the register/co2_bricklet/<UID>/co2_concentration callback is triggered periodically. A value of 0 turns the callback off.

The register/co2_bricklet/<UID>/co2_concentration callback is only triggered if the CO2 concentration has changed since the last triggering.

The default value is 0.

request/co2_bricklet/<UID>/get_co2_concentration_callback_period
Response payload:
 
  • period -- int

Returns the period as set by request/co2_bricklet/<UID>/set_co2_concentration_callback_period.

request/co2_bricklet/<UID>/set_co2_concentration_callback_threshold
Request payload:
 
  • option -- string (has symbols)
  • min -- int
  • max -- int

Sets the thresholds for the register/co2_bricklet/<UID>/co2_concentration_reached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the CO2 concentration is outside the min and max values
'i' Callback is triggered when the CO2 concentration is inside the min and max values
'<' Callback is triggered when the CO2 concentration is smaller than the min value (max is ignored)
'>' Callback is triggered when the CO2 concentration is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/co2_bricklet/<UID>/get_co2_concentration_callback_threshold
Response payload:
 
  • option -- string (has symbols)
  • min -- int
  • max -- int

Returns the threshold as set by request/co2_bricklet/<UID>/set_co2_concentration_callback_threshold.

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/co2_bricklet/<UID>/set_debounce_period
Request payload:
 
  • debounce -- int

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

request/co2_bricklet/<UID>/get_debounce_period
Response payload:
 
  • debounce -- int

Returns the debounce period as set by request/co2_bricklet/<UID>/set_debounce_period.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding .../register/... topic and an optional suffix. This suffix can be used to deregister the callback later.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

register/co2_bricklet/<UID>/co2_concentration
Request payload:
 
  • register -- bool
Response payload:
 
  • co2_concentration -- int

A callback can be registered for this event by publishing to the .../register/co2_bricklet/<UID>/co2_concentration[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/co2_bricklet/<UID>/co2_concentration[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically with the period that is set by request/co2_bricklet/<UID>/set_co2_concentration_callback_period. The callback payload is the CO2 concentration of the sensor.

The register/co2_bricklet/<UID>/co2_concentration callback is only triggered if the CO2 concentration has changed since the last triggering.

register/co2_bricklet/<UID>/co2_concentration_reached
Request payload:
 
  • register -- bool
Response payload:
 
  • co2_concentration -- int

A callback can be registered for this event by publishing to the .../register/co2_bricklet/<UID>/co2_concentration_reached[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/co2_bricklet/<UID>/co2_concentration_reached[/<SUFFIX>] topic for each registered suffix.

This callback is triggered when the threshold as set by request/co2_bricklet/<UID>/set_co2_concentration_callback_threshold is reached. The callback payload is the CO2 concentration.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by request/co2_bricklet/<UID>/set_debounce_period.