MQTT - Accelerometer Bricklet

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

setup:
    # Get current acceleration
    subscribe to tinkerforge/response/accelerometer_bricklet/XYZ/get_acceleration
    publish '' to tinkerforge/request/accelerometer_bricklet/XYZ/get_acceleration

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Accelerometer Bricklet

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

Threshold

Download (example-threshold.txt)

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# Change XYZ to the UID of your Accelerometer Bricklet

setup:
    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    publish '{"debounce": 10000}' to tinkerforge/request/accelerometer_bricklet/XYZ/set_debounce_period
    
    # Handle incoming acceleration reached callbacks
    subscribe to tinkerforge/callback/accelerometer_bricklet/XYZ/acceleration_reached
    publish '{"register": true}' to tinkerforge/register/accelerometer_bricklet/XYZ/acceleration_reached # Register acceleration_reached callback
    
    # Configure threshold for acceleration "greater than 2 g, 2 g, 2 g"
    publish '{"option": "greater", "min_x": 2000, "max_x": 0, "min_y": 2000, "max_y": 0, "min_z": 2000, "max_z": 0}' to tinkerforge/request/accelerometer_bricklet/XYZ/set_acceleration_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/accelerometer_bricklet/<UID>/get_acceleration
Response payload:
 
  • x -- int
  • y -- int
  • z -- int

Returns the acceleration in x, y and z direction. The values are given in g/1000 (1g = 9.80665m/s²), not to be confused with grams.

If you want to get the acceleration periodically, it is recommended to use the register/accelerometer_bricklet/<UID>/acceleration callback and set the period with request/accelerometer_bricklet/<UID>/set_acceleration_callback_period.

request/accelerometer_bricklet/<UID>/get_temperature
Response payload:
 
  • temperature -- int

Returns the temperature of the accelerometer in °C.

request/accelerometer_bricklet/<UID>/led_on

Enables the LED on the Bricklet.

request/accelerometer_bricklet/<UID>/led_off

Disables the LED on the Bricklet.

request/accelerometer_bricklet/<UID>/is_led_on
Response payload:
 
  • on -- bool

Returns true if the LED is enabled, false otherwise.

Advanced Functions

request/accelerometer_bricklet/<UID>/set_configuration
Request payload:
 
  • data_rate -- int (has symbols)
  • full_scale -- int (has symbols)
  • filter_bandwidth -- int (has symbols)

Configures the data rate, full scale range and filter bandwidth. Possible values are:

  • Data rate of 0Hz to 1600Hz.
  • Full scale range of -2G to +2G up to -16G to +16G.
  • Filter bandwidth between 50Hz and 800Hz.

Decreasing data rate or full scale range will also decrease the noise on the data.

The default values are 100Hz data rate, -4G to +4G range and 200Hz filter bandwidth.

The following symbols are available for this function:

for data_rate:

  • "Off" = 0
  • "3Hz" = 1
  • "6Hz" = 2
  • "12Hz" = 3
  • "25Hz" = 4
  • "50Hz" = 5
  • "100Hz" = 6
  • "400Hz" = 7
  • "800Hz" = 8
  • "1600Hz" = 9

for full_scale:

  • "2g" = 0
  • "4g" = 1
  • "6g" = 2
  • "8g" = 3
  • "16g" = 4

for filter_bandwidth:

  • "800Hz" = 0
  • "400Hz" = 1
  • "200Hz" = 2
  • "50Hz" = 3
request/accelerometer_bricklet/<UID>/get_configuration
Response payload:
 
  • data_rate -- int (has symbols)
  • full_scale -- int (has symbols)
  • filter_bandwidth -- int (has symbols)

Returns the configuration as set by request/accelerometer_bricklet/<UID>/set_configuration.

The following symbols are available for this function:

for data_rate:

  • "Off" = 0
  • "3Hz" = 1
  • "6Hz" = 2
  • "12Hz" = 3
  • "25Hz" = 4
  • "50Hz" = 5
  • "100Hz" = 6
  • "400Hz" = 7
  • "800Hz" = 8
  • "1600Hz" = 9

for full_scale:

  • "2g" = 0
  • "4g" = 1
  • "6g" = 2
  • "8g" = 3
  • "16g" = 4

for filter_bandwidth:

  • "800Hz" = 0
  • "400Hz" = 1
  • "200Hz" = 2
  • "50Hz" = 3
request/accelerometer_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 Accelerometer's name in a human readable form.

Callback Configuration Functions

request/accelerometer_bricklet/<UID>/set_acceleration_callback_period
Request payload:
 
  • period -- int

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

The register/accelerometer_bricklet/<UID>/acceleration callback is only triggered if the acceleration has changed since the last triggering.

The default value is 0.

request/accelerometer_bricklet/<UID>/get_acceleration_callback_period
Response payload:
 
  • period -- int

Returns the period as set by request/accelerometer_bricklet/<UID>/set_acceleration_callback_period.

request/accelerometer_bricklet/<UID>/set_acceleration_callback_threshold
Request payload:
 
  • option -- string (has symbols)
  • min_x -- int
  • max_x -- int
  • min_y -- int
  • max_y -- int
  • min_z -- int
  • max_z -- int

Sets the thresholds for the register/accelerometer_bricklet/<UID>/acceleration_reached callback.

The following options are possible:

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

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

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/accelerometer_bricklet/<UID>/get_acceleration_callback_threshold
Response payload:
 
  • option -- string (has symbols)
  • min_x -- int
  • max_x -- int
  • min_y -- int
  • max_y -- int
  • min_z -- int
  • max_z -- int

Returns the threshold as set by request/accelerometer_bricklet/<UID>/set_acceleration_callback_threshold.

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/accelerometer_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/accelerometer_bricklet/<UID>/get_debounce_period
Response payload:
 
  • debounce -- int

Returns the debounce period as set by request/accelerometer_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/accelerometer_bricklet/<UID>/acceleration
Request payload:
 
  • register -- bool
Response payload:
 
  • x -- int
  • y -- int
  • z -- int

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

This callback is triggered periodically with the period that is set by request/accelerometer_bricklet/<UID>/set_acceleration_callback_period. The callback payload members are the X, Y and Z acceleration.

The register/accelerometer_bricklet/<UID>/acceleration callback is only triggered if the acceleration has changed since the last triggering.

register/accelerometer_bricklet/<UID>/acceleration_reached
Request payload:
 
  • register -- bool
Response payload:
 
  • x -- int
  • y -- int
  • z -- int

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

This callback is triggered when the threshold as set by request/accelerometer_bricklet/<UID>/set_acceleration_callback_threshold is reached. The callback payload members are the X, Y and Z acceleration.

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