This is the description of the Python API bindings for the Dual Button Bricklet. General information and technical specifications for the Dual Button Bricklet are summarized in its hardware description.
An installation guide for the Python API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
Download (example_callback.py)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change to your UID
from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_dual_button import DualButton
# Callback function for state changed callback
def cb_state_changed(button_l, button_r, led_l, led_r):
if button_l == DualButton.BUTTON_STATE_PRESSED:
print('Left button pressed')
else:
print('Left button released')
if button_r == DualButton.BUTTON_STATE_PRESSED:
print('Right button pressed')
else:
print('Right button released')
print('')
if __name__ == "__main__":
ipcon = IPConnection() # Create IP connection
db = DualButton(UID, ipcon) # Create device object
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
# Register state changed callback to function cb_state_changed
db.register_callback(db.CALLBACK_STATE_CHANGED, cb_state_changed)
raw_input('Press key to exit\n') # Use input() in Python 3
ipcon.disconnect()
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Generally, every method of the Python bindings can throw an tinkerforge.ip_connection.Error exception that has a value and a description property. value can have different values:
All methods listed below are thread-safe.
Parameters: |
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Creates an object with the unique device ID uid:
dual_button = DualButton("YOUR_DEVICE_UID", ipcon)
This object can then be used after the IP Connection is connected (see examples above).
Parameters: |
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Return type: | None |
Sets the state of the LEDs. Possible states are:
In auto toggle mode the LED is toggled automatically at each press of a button.
If you just want to set one of the LEDs and don't know the current state of the other LED, you can get the state with get_led_state() or you can use set_selected_led_state().
The default value is (1, 1).
The following constants are available for this function:
Return type: | (int, int) |
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Returns the current state of the LEDs, as set by set_led_state().
The following constants are available for this function:
The returned namedtuple has the variables led_l and led_r.
Return type: | (int, int) |
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Returns the current state for both buttons. Possible states are:
The following constants are available for this function:
The returned namedtuple has the variables button_l and button_r.
Parameters: |
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Return type: | None |
Sets the state of the selected LED (0 or 1).
The other LED remains untouched.
The following constants are available for this function:
Return type: | [int, int, int] |
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Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.
Parameters: | function_id -- int |
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Return type: | bool |
Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.
For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by set_response_expected(). For setter functions it is disabled by default and can be enabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.
See set_response_expected() for the list of function ID constants available for this function.
Parameters: |
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Return type: | None |
Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled and callbacks it is always disabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.
The following function ID constants are available for this function:
Parameters: | response_expected -- bool |
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Return type: | None |
Changes the response expected flag for all setter and callback configuration functions of this device at once.
Return type: | (str, str, chr, [int, int, int], [int, int, int], int) |
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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. There is also a constant for the device identifier of this Bricklet.
The returned namedtuple has the variables uid, connected_uid, position, hardware_version, firmware_version and device_identifier.
Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the register_callback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:
def my_callback(param):
print(param)
dual_button.register_callback(DualButton.CALLBACK_EXAMPLE, my_callback)
The available constants with inherent number and type of parameters are described below.
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.
Parameters: |
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This callback is called whenever a button is pressed.
Possible states for buttons are:
Possible states for LEDs are:
The following constants are available for this function:
This constant is used to identify a Dual Button Bricklet.
The get_identity() function and the CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.