MQTT - Dust Detector Bricklet

This is the description of the MQTT API bindings for the Dust Detector Bricklet. General information and technical specifications for the Dust Detector 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 Dust Detector Bricklet

setup:
    # Get current dust density
    subscribe to tinkerforge/response/dust_detector_bricklet/XYZ/get_dust_density
    publish '' to tinkerforge/request/dust_detector_bricklet/XYZ/get_dust_density

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Dust Detector Bricklet

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

Threshold

Download (example-threshold.txt)

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# Change XYZ to the UID of your Dust Detector Bricklet

setup:
    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    publish '{"debounce": 10000}' to tinkerforge/request/dust-detector_bricklet/XYZ/set_debounce_period
    
    # Handle incoming dust density reached callbacks
    subscribe to tinkerforge/callback/dust_detector_bricklet/XYZ/dust_density_reached
    publish '{"register": true}' to tinkerforge/register/dust_detector_bricklet/XYZ/dust_density_reached # Register dust_density_reached callback
    
    # Configure threshold for dust density "greater than 10 µg/m³"
    publish '{"option": "greater", "min": 10, "max": 0}' to tinkerforge/request/dust_detector_bricklet/XYZ/set_dust_density_callback_threshold

API

All published payloads to and from the MQTT bindings are in 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/dust_detector_bricklet/<UID>/get_dust_density
Response payload:
  • dust_density -- int

Returns the dust density in µg/m³.

If you want to get the dust density periodically, it is recommended to use the register/dust_detector_bricklet/<UID>/dust_density callback and set the period with request/dust_detector_bricklet/<UID>/set_dust_density_callback_period.

Advanced Functions

request/dust_detector_bricklet/<UID>/set_moving_average
Request payload:
  • average -- int

Sets the length of a moving averaging for the dust density.

Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.

The range for the averaging is 0-100.

The default value is 100.

request/dust_detector_bricklet/<UID>/get_moving_average
Response payload:
  • average -- int

Returns the length moving average as set by request/dust_detector_bricklet/<UID>/set_moving_average.

request/dust_detector_bricklet/<UID>/get_identity
Response payload:
  • uid -- string
  • connected_uid -- string
  • position -- char
  • 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 Dust Detector's name in a human readable form.

Callback Configuration Functions

request/dust_detector_bricklet/<UID>/set_dust_density_callback_period
Request payload:
  • period -- int

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

The register/dust_detector_bricklet/<UID>/dust_density callback is only triggered if the dust density has changed since the last triggering.

The default value is 0.

request/dust_detector_bricklet/<UID>/get_dust_density_callback_period
Response payload:
  • period -- int

Returns the period as set by request/dust_detector_bricklet/<UID>/set_dust_density_callback_period.

request/dust_detector_bricklet/<UID>/set_dust_density_callback_threshold
Request payload:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Sets the thresholds for the register/dust_detector_bricklet/<UID>/dust_density_reached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the dust density value is outside the min and max values
'i' Callback is triggered when the dust density value is inside the min and max values
'<' Callback is triggered when the dust density value is smaller than the min value (max is ignored)
'>' Callback is triggered when the dust density value 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/dust_detector_bricklet/<UID>/get_dust_density_callback_threshold
Response payload:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Returns the threshold as set by request/dust_detector_bricklet/<UID>/set_dust_density_callback_threshold.

The following symbols are available for this function:

for option:

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

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

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

Returns the debounce period as set by request/dust_detector_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/dust_detector_bricklet/<UID>/dust_density
Request payload:
  • register -- bool
Response payload:
  • dust_density -- int

A callback can be registered for this event by publishing to the .../register/dust_detector_bricklet/<UID>/dust_density[/<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/dust_detector_bricklet/<UID>/dust_density[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically with the period that is set by request/dust_detector_bricklet/<UID>/set_dust_density_callback_period. The callback payload is the dust density of the sensor.

Der register/dust_detector_bricklet/<UID>/dust_density callback is only triggered if the dust density value has changed since the last triggering.

register/dust_detector_bricklet/<UID>/dust_density_reached
Request payload:
  • register -- bool
Response payload:
  • dust_density -- int

A callback can be registered for this event by publishing to the .../register/dust_detector_bricklet/<UID>/dust_density_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/dust_detector_bricklet/<UID>/dust_density_reached[/<SUFFIX>] topic for each registered suffix.

This callback is triggered when the threshold as set by request/dust_detector_bricklet/<UID>/set_dust_density_callback_threshold is reached. The callback payload is the dust density of the sensor.

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