MQTT - Joystick Bricklet

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

setup:
    # Get current position
    subscribe to tinkerforge/response/joystick_bricklet/XYZ/get_position
    publish '' to tinkerforge/request/joystick_bricklet/XYZ/get_position

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Joystick Bricklet

setup:
    # Handle incoming pressed callbacks
    subscribe to tinkerforge/callback/joystick_bricklet/XYZ/pressed
    publish '{"register": true}' to tinkerforge/register/joystick_bricklet/XYZ/pressed # Register pressed callback
    
    # Handle incoming released callbacks
    subscribe to tinkerforge/callback/joystick_bricklet/XYZ/released
    publish '{"register": true}' to tinkerforge/register/joystick_bricklet/XYZ/released # Register released callback

Find Borders

Download (example-find-borders.txt)

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# Change XYZ to the UID of your Joystick Bricklet

setup:
    # Get threshold callbacks with a debounce time of 0.2 seconds (200ms)
    publish '{"debounce": 200}' to tinkerforge/request/joystick_bricklet/XYZ/set_debounce_period
    
    # Handle incoming position reached callbacks
    subscribe to tinkerforge/callback/joystick_bricklet/XYZ/position_reached
        if a message arrives
            # message contains x and y as int
            if y == 100
                print "Top"
            elseif y == -100
                print "Bottom"
            elseif x == 100
                print "Right"
            elseif x == -100
                print "Left"
            endif           
            print "\n"
    endsubscribe
    
    publish '{"register": true}' to tinkerforge/register/joystick_bricklet/XYZ/position_reached
    
    # Configure threshold for position "outside of -99, -99 to 99, 99"
    publish '{"option": "outside", "min_x": -99, "max_x": 99, "min_y": -99, "max_y": 99}' to tinkerforge/request/joystick_bricklet/XYZ/set_position_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/joystick_bricklet/<UID>/get_position
Response payload:
 
  • x -- int
  • y -- int

Returns the position of the joystick. The value ranges between -100 and 100 for both axis. The middle position of the joystick is x=0, y=0. The returned values are averaged and calibrated (see request/joystick_bricklet/<UID>/calibrate).

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

request/joystick_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/joystick_bricklet/<UID>/pressed and register/joystick_bricklet/<UID>/released callbacks to handle the button.

Advanced Functions

request/joystick_bricklet/<UID>/get_analog_value
Response payload:
 
  • x -- int
  • y -- int

Returns the values as read by a 12-bit analog-to-digital converter. The values are between 0 and 4095 for both axis.

Note

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

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

request/joystick_bricklet/<UID>/calibrate

Calibrates the middle position of the joystick. If your Joystick Bricklet does not return x=0 and y=0 in the middle position, call this function while the joystick is standing still in the middle position.

The resulting calibration will be saved on the EEPROM of the Joystick Bricklet, thus you only have to calibrate it once.

request/joystick_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 Joystick's name in a human readable form.

Callback Configuration Functions

request/joystick_bricklet/<UID>/set_position_callback_period
Request payload:
 
  • period -- int

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

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

The default value is 0.

request/joystick_bricklet/<UID>/get_position_callback_period
Response payload:
 
  • period -- int

Returns the period as set by request/joystick_bricklet/<UID>/set_position_callback_period.

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

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

The register/joystick_bricklet/<UID>/analog_value callback is only triggered if the analog values have changed since the last triggering.

The default value is 0.

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

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

request/joystick_bricklet/<UID>/set_position_callback_threshold
Request payload:
 
  • option -- string (has symbols)
  • min_x -- int
  • max_x -- int
  • min_y -- int
  • max_y -- int

Sets the thresholds for the register/joystick_bricklet/<UID>/position_reached callback.

The following options are possible:

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

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

The following symbols are available for this function:

for option:

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

Returns the threshold as set by request/joystick_bricklet/<UID>/set_position_callback_threshold.

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/joystick_bricklet/<UID>/set_analog_value_callback_threshold
Request payload:
 
  • option -- string (has symbols)
  • min_x -- int
  • max_x -- int
  • min_y -- int
  • max_y -- int

Sets the thresholds for the register/joystick_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 values are outside the min and max values
'i' Callback is triggered when the analog values are inside the min and max values
'<' Callback is triggered when the analog values are smaller than the min values (max is ignored)
'>' Callback is triggered when the analog values are greater than the min values (max is ignored)

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

The following symbols are available for this function:

for option:

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

Returns the threshold as set by request/joystick_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/joystick_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/joystick_bricklet/<UID>/get_debounce_period
Response payload:
 
  • debounce -- int

Returns the debounce period as set by request/joystick_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/joystick_bricklet/<UID>/position
Request payload:
 
  • register -- bool
Response payload:
 
  • x -- int
  • y -- int

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

This callback is triggered periodically with the period that is set by request/joystick_bricklet/<UID>/set_position_callback_period. The callback payload is the position of the joystick.

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

register/joystick_bricklet/<UID>/analog_value
Request payload:
 
  • register -- bool
Response payload:
 
  • x -- int
  • y -- int

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

This callback is triggered periodically with the period that is set by request/joystick_bricklet/<UID>/set_analog_value_callback_period. The callback payload members are the analog values of the joystick.

The register/joystick_bricklet/<UID>/analog_value callback is only triggered if the values have changed since the last triggering.

register/joystick_bricklet/<UID>/position_reached
Request payload:
 
  • register -- bool
Response payload:
 
  • x -- int
  • y -- int

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

This callback is triggered when the threshold as set by request/joystick_bricklet/<UID>/set_position_callback_threshold is reached. The callback payload members are the position of the joystick.

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

register/joystick_bricklet/<UID>/analog_value_reached
Request payload:
 
  • register -- bool
Response payload:
 
  • x -- int
  • y -- int

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

This callback is triggered when the threshold as set by request/joystick_bricklet/<UID>/set_analog_value_callback_threshold is reached. The callback payload members are the analog values of the joystick.

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

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

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

This callback is triggered when the button is pressed.

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

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

This callback is triggered when the button is released.