1# Change XYZ to the UID of your Dual Button Bricklet23setup:4# Handle incoming state changed callbacks5subscribetotinkerforge/callback/dual_button_bricklet/XYZ/state_changed6publish'{"register": true}'totinkerforge/register/dual_button_bricklet/XYZ/state_changed# Register state_changed callback
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 member _ERROR.
It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....
device_identifier – Type: int, Range: [0 to 216 - 1]
_display_name – Type: 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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port).
A Bricklet connected to an Isolator Bricklet is always at
position 'z'.
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 Dual Button's name in a human readable form.
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.
A callback can be registered for this event by publishing to the .../register/dual_button_bricklet/<UID>/state_changed[/<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/dual_button_bricklet/<UID>/state_changed[/<SUFFIX>] topic for each registered suffix.
This callback is called whenever a button is pressed.
Possible states for buttons are:
0 = pressed
1 = released
Possible states for LEDs are:
0 = AutoToggleOn: Auto toggle enabled and LED on.
1 = AutoToggleOff: Auto toggle enabled and LED off.
2 = On: LED on (auto toggle is disabled).
3 = Off: LED off (auto toggle is disabled).
The following symbols are available for this function: