MQTT - Distance IR Bricklet

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

setup:
    # Get current distance
    subscribe to tinkerforge/response/distance_ir_bricklet/XYZ/get_distance
    publish '' to tinkerforge/request/distance_ir_bricklet/XYZ/get_distance 

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Distance IR Bricklet

setup:
    # Handle incoming distance callbacks
    subscribe to tinkerforge/callback/distance_ir_bricklet/XYZ/distance
    publish '{"register": true}' to tinkerforge/register/distance_ir_bricklet/XYZ/distance # Register distance callback
    
    # Set period for distance callback to 0.2s (200ms)
    # Note: The distance callback is only called every 0.2 seconds
    #       if the distance has changed since the last call!
    publish '{"period": 200}' to tinkerforge/request/distance_ir_bricklet/XYZ/set_distance_callback_period

Threshold

Download (example-threshold.txt)

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# Change XYZ to the UID of your Distance IR Bricklet

setup:
    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    publish '{"debounce": 10000}' to tinkerforge/request/distance-ir_bricklet/XYZ/set_debounce_period
    
    # Handle incoming distance reached callbacks
    subscribe to tinkerforge/callback/distance_ir_bricklet/XYZ/distance_reached
    publish '{"register": true}' to tinkerforge/register/distance_ir_bricklet/XYZ/distance_reached # Register distance_reached callback
    
    # Configure threshold for distance "smaller than 30 cm"
    publish '{"option": "smaller", "min": 300, "max": 0}' to tinkerforge/request/distance_ir_bricklet/XYZ/set_distance_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/distance_ir_bricklet/<UID>/get_distance
Response payload:
 
  • distance -- int

Returns the distance measured by the sensor. The value is in mm and possible distance ranges are 40 to 300, 100 to 800 and 200 to 1500, depending on the selected IR sensor.

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

Advanced Functions

request/distance_ir_bricklet/<UID>/get_analog_value
Response payload:
 
  • value -- int

Returns the value as read by a 12-bit analog-to-digital converter. The value is between 0 and 4095.

Note

The value returned by request/distance_ir_bricklet/<UID>/get_distance is averaged over several samples to yield less noise, while request/distance_ir_bricklet/<UID>/get_analog_value gives back raw unfiltered analog values. The only reason to use request/distance_ir_bricklet/<UID>/get_analog_value is, if you need the full resolution of the analog-to-digital converter.

If you want the analog value periodically, it is recommended to use the register/distance_ir_bricklet/<UID>/analog_value callback and set the period with request/distance_ir_bricklet/<UID>/set_analog_value_callback_period.

request/distance_ir_bricklet/<UID>/set_sampling_point
Request payload:
 
  • position -- int
  • distance -- int

Sets a sampling point value to a specific position of the lookup table. The lookup table comprises 128 equidistant analog values with corresponding distances.

If you measure a distance of 50cm at the analog value 2048, you should call this function with (64, 5000). The utilized analog-to-digital converter has a resolution of 12 bit. With 128 sampling points on the whole range, this means that every sampling point has a size of 32 analog values. Thus the analog value 2048 has the corresponding sampling point 64 = 2048/32.

Sampling points are saved on the EEPROM of the Distance IR Bricklet and loaded again on startup.

Note

An easy way to calibrate the sampling points of the Distance IR Bricklet is implemented in the Brick Viewer. If you want to calibrate your Bricklet it is highly recommended to use this implementation.

request/distance_ir_bricklet/<UID>/get_sampling_point
Request payload:
 
  • position -- int
Response payload:
 
  • distance -- int

Returns the distance to a sampling point position as set by request/distance_ir_bricklet/<UID>/set_sampling_point.

request/distance_ir_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 Distance IR's name in a human readable form.

Callback Configuration Functions

request/distance_ir_bricklet/<UID>/set_distance_callback_period
Request payload:
 
  • period -- int

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

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

The default value is 0.

request/distance_ir_bricklet/<UID>/get_distance_callback_period
Response payload:
 
  • period -- int

Returns the period as set by request/distance_ir_bricklet/<UID>/set_distance_callback_period.

request/distance_ir_bricklet/<UID>/set_analog_value_callback_period
Request payload:
 
  • period -- int

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

The register/distance_ir_bricklet/<UID>/analog_value callback is only triggered if the analog value has changed since the last triggering.

The default value is 0.

request/distance_ir_bricklet/<UID>/get_analog_value_callback_period
Response payload:
 
  • period -- int

Returns the period as set by request/distance_ir_bricklet/<UID>/set_analog_value_callback_period.

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

Sets the thresholds for the register/distance_ir_bricklet/<UID>/distance_reached callback.

The following options are possible:

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

Returns the threshold as set by request/distance_ir_bricklet/<UID>/set_distance_callback_threshold.

The following symbols are available for this function:

for option:

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

Sets the thresholds for the register/distance_ir_bricklet/<UID>/analog_value_reached callback.

The following options are possible:

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

Returns the threshold as set by request/distance_ir_bricklet/<UID>/set_analog_value_callback_threshold.

The following symbols are available for this function:

for option:

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

Returns the debounce period as set by request/distance_ir_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/distance_ir_bricklet/<UID>/distance
Request payload:
 
  • register -- bool
Response payload:
 
  • distance -- int

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

This callback is triggered periodically with the period that is set by request/distance_ir_bricklet/<UID>/set_distance_callback_period. The callback payload is the distance of the sensor.

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

register/distance_ir_bricklet/<UID>/analog_value
Request payload:
 
  • register -- bool
Response payload:
 
  • value -- int

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

This callback is triggered periodically with the period that is set by request/distance_ir_bricklet/<UID>/set_analog_value_callback_period. The callback payload is the analog value of the sensor.

The register/distance_ir_bricklet/<UID>/analog_value callback is only triggered if the analog value has changed since the last triggering.

register/distance_ir_bricklet/<UID>/distance_reached
Request payload:
 
  • register -- bool
Response payload:
 
  • distance -- int

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

This callback is triggered when the threshold as set by request/distance_ir_bricklet/<UID>/set_distance_callback_threshold is reached. The callback payload is the distance of the sensor.

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

register/distance_ir_bricklet/<UID>/analog_value_reached
Request payload:
 
  • register -- bool
Response payload:
 
  • value -- int

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

This callback is triggered when the threshold as set by request/distance_ir_bricklet/<UID>/set_analog_value_callback_threshold is reached. The callback payload is the analog value of the sensor.

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