MQTT - Rotary Encoder Bricklet

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

setup:
    # Get current count without reset
    subscribe to tinkerforge/response/rotary_encoder_bricklet/XYZ/get_count
    publish '{"reset": false}' to tinkerforge/request/rotary_encoder_bricklet/XYZ/get_count

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Rotary Encoder Bricklet

setup:
    # Handle incoming count callbacks
    subscribe to tinkerforge/callback/rotary_encoder_bricklet/XYZ/count
    publish '{"register": true}' to tinkerforge/register/rotary_encoder_bricklet/XYZ/count # Register count callback
    
    # Set period for count callback to 0.05s (50ms)
    # Note: The count callback is only called every 0.05 seconds
    #       if the count has changed since the last call!
    publish '{"period": 50}' to tinkerforge/request/rotary_encoder_bricklet/XYZ/set_count_callback_period

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/rotary_encoder_bricklet/<UID>/get_count
Request payload:
  • reset -- bool
Response payload:
  • count -- int

Returns the current count of the encoder. If you set reset to true, the count is set back to 0 directly after the current count is read.

The encoder has 24 steps per rotation

Turning the encoder to the left decrements the counter, so a negative count is possible.

request/rotary_encoder_bricklet/<UID>/is_pressed
Response payload:
  • pressed -- bool

Returns true if the button is pressed and false otherwise.

It is recommended to use the register/rotary_encoder_bricklet/<UID>/pressed and register/rotary_encoder_bricklet/<UID>/released callbacks to handle the button.

Advanced Functions

request/rotary_encoder_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 Rotary Encoder's name in a human readable form.

Callback Configuration Functions

request/rotary_encoder_bricklet/<UID>/set_count_callback_period
Request payload:
  • period -- int

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

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

The default value is 0.

request/rotary_encoder_bricklet/<UID>/get_count_callback_period
Response payload:
  • period -- int

Returns the period as set by request/rotary_encoder_bricklet/<UID>/set_count_callback_period.

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

Sets the thresholds for the register/rotary_encoder_bricklet/<UID>/count_reached callback.

The following options are possible:

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

Returns the threshold as set by request/rotary_encoder_bricklet/<UID>/set_count_callback_threshold.

The following symbols are available for this function:

for option:

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

Sets the period in ms with which the threshold callback

is triggered, if the thresholds

keeps being reached.

The default value is 100.

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

Returns the debounce period as set by request/rotary_encoder_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/rotary_encoder_bricklet/<UID>/count
Request payload:
  • register -- bool
Response payload:
  • count -- int

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

This callback is triggered periodically with the period that is set by request/rotary_encoder_bricklet/<UID>/set_count_callback_period. The callback payload is the count of the encoder.

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

register/rotary_encoder_bricklet/<UID>/count_reached
Request payload:
  • register -- bool
Response payload:
  • count -- int

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

This callback is triggered when the threshold as set by request/rotary_encoder_bricklet/<UID>/set_count_callback_threshold is reached. The callback payload is the count of the encoder.

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

register/rotary_encoder_bricklet/<UID>/pressed
Request payload:
  • register -- bool

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

This callback is triggered when the button is pressed.

register/rotary_encoder_bricklet/<UID>/released
Request payload:
  • register -- bool

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

This callback is triggered when the button is released.