Python - Multi Touch Bricklet 2.0

This is the description of the Python API bindings for the Multi Touch Bricklet 2.0. General information and technical specifications for the Multi Touch Bricklet 2.0 are summarized in its hardware description.

An installation guide for the Python API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example_simple.py)

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Multi Touch Bricklet 2.0

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_multi_touch_v2 import BrickletMultiTouchV2

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    mt = BrickletMultiTouchV2(UID, ipcon) # Create device object

    ipcon.connect(HOST, PORT) # Connect to brickd
    # Don't use device before ipcon is connected

    # Get current touch state
    state = mt.get_touch_state()

    print("Electrode 0: " + str(state[0]))
    print("Electrode 1: " + str(state[1]))
    print("Electrode 2: " + str(state[2]))
    print("Electrode 3: " + str(state[3]))
    print("Electrode 4: " + str(state[4]))
    print("Electrode 5: " + str(state[5]))
    print("Electrode 6: " + str(state[6]))
    print("Electrode 7: " + str(state[7]))
    print("Electrode 8: " + str(state[8]))
    print("Electrode 9: " + str(state[9]))
    print("Electrode 10: " + str(state[10]))
    print("Electrode 11: " + str(state[11]))
    print("Proximity: " + str(state[12]))

    raw_input("Press key to exit\n") # Use input() in Python 3
    ipcon.disconnect()

Callback

Download (example_callback.py)

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Multi Touch Bricklet 2.0

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_multi_touch_v2 import BrickletMultiTouchV2

# Callback function for touch state callback
def cb_touch_state(state):
    print("Electrode 0: " + str(state[0]))
    print("Electrode 1: " + str(state[1]))
    print("Electrode 2: " + str(state[2]))
    print("Electrode 3: " + str(state[3]))
    print("Electrode 4: " + str(state[4]))
    print("Electrode 5: " + str(state[5]))
    print("Electrode 6: " + str(state[6]))
    print("Electrode 7: " + str(state[7]))
    print("Electrode 8: " + str(state[8]))
    print("Electrode 9: " + str(state[9]))
    print("Electrode 10: " + str(state[10]))
    print("Electrode 11: " + str(state[11]))
    print("Proximity: " + str(state[12]))
    print("")

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    mt = BrickletMultiTouchV2(UID, ipcon) # Create device object

    ipcon.connect(HOST, PORT) # Connect to brickd
    # Don't use device before ipcon is connected

    # Register touch state callback to function cb_touch_state
    mt.register_callback(mt.CALLBACK_TOUCH_STATE, cb_touch_state)

    # Set period for touch state callback to 0.01s (10ms)
    mt.set_touch_state_callback_configuration(10, True)

    raw_input("Press key to exit\n") # Use input() in Python 3
    ipcon.disconnect()

API

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:

  • Error.TIMEOUT = -1
  • Error.NOT_ADDED = -6 (unused since Python bindings version 2.0.0)
  • Error.ALREADY_CONNECTED = -7
  • Error.NOT_CONNECTED = -8
  • Error.INVALID_PARAMETER = -9
  • Error.NOT_SUPPORTED = -10
  • Error.UNKNOWN_ERROR_CODE = -11
  • Error.STREAM_OUT_OF_SYNC = -12
  • Error.INVALID_UID = -13
  • Error.NON_ASCII_CHAR_IN_SECRET = -14

All methods listed below are thread-safe.

Basic Functions

BrickletMultiTouchV2(uid, ipcon)
Parameters:
  • uid -- string
  • ipcon -- IPConnection

Creates an object with the unique device ID uid:

multi_touch_v2 = BrickletMultiTouchV2("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected (see examples above).

BrickletMultiTouchV2.get_touch_state()
Return type:[bool, bool, ..10x.., bool]

Returns the current touch state. The state is given as a array of bools.

Element 0 to 11 represent the 12 electrodes and element 12 represents the proximity.

If an electrode is touched, the corresponding element is true. If a hand or similar is in proximity to the electrodes, element 12 is true.

The proximity is activated with a distance of 1-2cm. An electrode is already counted as touched if a finger is nearly touching the electrode. This means that you can put a piece of paper or foil or similar on top of a electrode to build a touch panel with a professional look.

If you want to get the value periodically, it is recommended to use the CALLBACK_TOUCH_STATE callback. You can set the callback configuration with set_touch_state_callback_configuration().

BrickletMultiTouchV2.recalibrate()
Return type:None

Recalibrates the electrodes. Call this function whenever you changed or moved you electrodes.

BrickletMultiTouchV2.set_electrode_config(enabled_electrodes)
Parameters:enabled_electrodes -- [bool, bool, ..10x.., bool]
Return type:None

Enables/disables electrodes with a bool array (see get_touch_state()).

True enables the electrode, false disables the electrode. A disabled electrode will always return false as its state. If you don't need all electrodes you can disable the electrodes that are not needed.

It is recommended that you disable the proximity electrode (element 12) if the proximity feature is not needed. This will reduce the amount of traffic that is produced by the CALLBACK_TOUCH_STATE callback.

Disabling electrodes will also reduce power consumption.

Default: All electrodes enabled.

BrickletMultiTouchV2.get_electrode_config()
Return type:[bool, bool, ..10x.., bool]

Returns the electrode configuration, as set by set_electrode_config().

BrickletMultiTouchV2.set_electrode_sensitivity(sensitivity)
Parameters:sensitivity -- int
Return type:None

Sets the sensitivity of the electrodes. An electrode with a high sensitivity will register a touch earlier then an electrode with a low sensitivity.

If you build a big electrode you might need to decrease the sensitivity, since the area that can be charged will get bigger. If you want to be able to activate an electrode from further away you need to increase the sensitivity.

After a new sensitivity is set, you likely want to call recalibrate() to calibrate the electrodes with the newly defined sensitivity.

The valid sensitivity value range is 5-201.

The default sensitivity value is 181.

BrickletMultiTouchV2.get_electrode_sensitivity()
Return type:int

Returns the current sensitivity, as set by set_electrode_sensitivity().

BrickletMultiTouchV2.set_touch_led_config(config)
Parameters:config -- int
Return type:None

Configures the touch LED to be either turned off, turned on, blink in heartbeat mode or show the touch state (electrode touched = LED on).

The default value is 3 (show touch state).

The following constants are available for this function:

  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_OFF = 0
  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_ON = 1
  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_SHOW_TOUCH = 3
BrickletMultiTouchV2.get_touch_led_config()
Return type:int

Returns the LED configuration as set by set_touch_led_config()

The following constants are available for this function:

  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_OFF = 0
  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_ON = 1
  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletMultiTouchV2.TOUCH_LED_CONFIG_SHOW_TOUCH = 3

Advanced Functions

BrickletMultiTouchV2.get_api_version()
Return type:[int, int, int]

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.

BrickletMultiTouchV2.get_response_expected(function_id)
Parameters:function_id -- int
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.

The following constants are available for this function:

  • BrickletMultiTouchV2.FUNCTION_SET_TOUCH_STATE_CALLBACK_CONFIGURATION = 2
  • BrickletMultiTouchV2.FUNCTION_RECALIBRATE = 5
  • BrickletMultiTouchV2.FUNCTION_SET_ELECTRODE_CONFIG = 6
  • BrickletMultiTouchV2.FUNCTION_SET_ELECTRODE_SENSITIVITY = 8
  • BrickletMultiTouchV2.FUNCTION_SET_TOUCH_LED_CONFIG = 10
  • BrickletMultiTouchV2.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletMultiTouchV2.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletMultiTouchV2.FUNCTION_RESET = 243
  • BrickletMultiTouchV2.FUNCTION_WRITE_UID = 248
BrickletMultiTouchV2.set_response_expected(function_id, response_expected)
Parameters:
  • function_id -- int
  • response_expected -- bool
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.

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 constants are available for this function:

  • BrickletMultiTouchV2.FUNCTION_SET_TOUCH_STATE_CALLBACK_CONFIGURATION = 2
  • BrickletMultiTouchV2.FUNCTION_RECALIBRATE = 5
  • BrickletMultiTouchV2.FUNCTION_SET_ELECTRODE_CONFIG = 6
  • BrickletMultiTouchV2.FUNCTION_SET_ELECTRODE_SENSITIVITY = 8
  • BrickletMultiTouchV2.FUNCTION_SET_TOUCH_LED_CONFIG = 10
  • BrickletMultiTouchV2.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletMultiTouchV2.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletMultiTouchV2.FUNCTION_RESET = 243
  • BrickletMultiTouchV2.FUNCTION_WRITE_UID = 248
BrickletMultiTouchV2.set_response_expected_all(response_expected)
Parameters:response_expected -- bool
Return type:None

Changes the response expected flag for all setter and callback configuration functions of this device at once.

BrickletMultiTouchV2.get_spitfp_error_count()
Return type:(int, int, int, int)

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

The returned namedtuple has the variables error_count_ack_checksum, error_count_message_checksum, error_count_frame and error_count_overflow.

BrickletMultiTouchV2.set_bootloader_mode(mode)
Parameters:mode -- int
Return type:int

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following constants are available for this function:

  • BrickletMultiTouchV2.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletMultiTouchV2.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletMultiTouchV2.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletMultiTouchV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletMultiTouchV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
  • BrickletMultiTouchV2.BOOTLOADER_STATUS_OK = 0
  • BrickletMultiTouchV2.BOOTLOADER_STATUS_INVALID_MODE = 1
  • BrickletMultiTouchV2.BOOTLOADER_STATUS_NO_CHANGE = 2
  • BrickletMultiTouchV2.BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • BrickletMultiTouchV2.BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • BrickletMultiTouchV2.BOOTLOADER_STATUS_CRC_MISMATCH = 5
BrickletMultiTouchV2.get_bootloader_mode()
Return type:int

Returns the current bootloader mode, see set_bootloader_mode().

The following constants are available for this function:

  • BrickletMultiTouchV2.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletMultiTouchV2.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletMultiTouchV2.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletMultiTouchV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletMultiTouchV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
BrickletMultiTouchV2.set_write_firmware_pointer(pointer)
Parameters:pointer -- int
Return type:None

Sets the firmware pointer for write_firmware(). The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletMultiTouchV2.write_firmware(data)
Parameters:data -- [int, int, ..61x.., int]
Return type:int

Writes 64 Bytes of firmware at the position as written by set_write_firmware_pointer() before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletMultiTouchV2.set_status_led_config(config)
Parameters:config -- int
Return type:None

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following constants are available for this function:

  • BrickletMultiTouchV2.STATUS_LED_CONFIG_OFF = 0
  • BrickletMultiTouchV2.STATUS_LED_CONFIG_ON = 1
  • BrickletMultiTouchV2.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletMultiTouchV2.STATUS_LED_CONFIG_SHOW_STATUS = 3
BrickletMultiTouchV2.get_status_led_config()
Return type:int

Returns the configuration as set by set_status_led_config()

The following constants are available for this function:

  • BrickletMultiTouchV2.STATUS_LED_CONFIG_OFF = 0
  • BrickletMultiTouchV2.STATUS_LED_CONFIG_ON = 1
  • BrickletMultiTouchV2.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletMultiTouchV2.STATUS_LED_CONFIG_SHOW_STATUS = 3
BrickletMultiTouchV2.get_chip_temperature()
Return type:int

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

BrickletMultiTouchV2.reset()
Return type:None

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

BrickletMultiTouchV2.write_uid(uid)
Parameters:uid -- int
Return type:None

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

BrickletMultiTouchV2.read_uid()
Return type:int

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

BrickletMultiTouchV2.get_identity()
Return type:(str, str, chr, [int, int, int], [int, int, int], int)

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.

Callback Configuration Functions

BrickletMultiTouchV2.register_callback(callback_id, function)
Parameters:
  • callback_id -- int
  • function -- callable
Return type:

None

Registers the given function with the given callback_id.

The available callback IDs with corresponding function signatures are listed below.

BrickletMultiTouchV2.set_touch_state_callback_configuration(period, value_has_to_change)
Parameters:
  • period -- int
  • value_has_to_change -- bool
Return type:

None

The period in ms is the period with which the CALLBACK_TOUCH_STATE callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

The default value is (0, false).

BrickletMultiTouchV2.get_touch_state_callback_configuration()
Return type:(int, bool)

Returns the callback configuration as set by set_touch_state_callback_configuration().

The returned namedtuple has the variables period and value_has_to_change.

Callbacks

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)

multi_touch_v2.register_callback(BrickletMultiTouchV2.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.

BrickletMultiTouchV2.CALLBACK_TOUCH_STATE
Parameters:state -- [bool, bool, ..10x.., bool]

Returns the current touch state, see get_touch_state() for information about the state.

This callback is triggered every time the touch state changes with a given period (see set_touch_state_callback_configuration())

Constants

BrickletMultiTouchV2.DEVICE_IDENTIFIER

This constant is used to identify a Multi Touch Bricklet 2.0.

The get_identity() function and the IPConnection.CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

BrickletMultiTouchV2.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Multi Touch Bricklet 2.0.