Python - Motorized Linear Poti Bricklet

This is the description of the Python API bindings for the Motorized Linear Poti Bricklet. General information and technical specifications for the Motorized Linear Poti Bricklet 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 Motorized Linear Poti Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_motorized_linear_poti import BrickletMotorizedLinearPoti

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

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

    # Get current position
    position = mlp.get_position()
    print("Position: " + str(position)) # Range: 0 to 100

    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 Motorized Linear Poti Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_motorized_linear_poti import BrickletMotorizedLinearPoti

# Callback function for position callback
def cb_position(position):
    print("Position: " + str(position)) # Range: 0 to 100

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

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

    # Register position callback to function cb_position
    mlp.register_callback(mlp.CALLBACK_POSITION, cb_position)

    # Set period for position callback to 0.05s (50ms) without a threshold
    mlp.set_position_callback_configuration(50, False, "x", 0, 0)

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

Motor

Download (example_motor.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 Motorized Linear Poti Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_motorized_linear_poti import BrickletMotorizedLinearPoti

# Callback function for position reached callback
def cb_position_reached(position):
    print("Position: " + str(position)) # Range: 0 to 100

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

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

    # Register position reached callback to function cb_position_reached
    mlp.register_callback(mlp.CALLBACK_POSITION_REACHED, cb_position_reached)

    # Move slider smooth to the middle
    mlp.set_motor_position(50, mlp.DRIVE_MODE_SMOOTH, False)

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

API

Generally, every function 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 functions listed below are thread-safe.

Basic Functions

BrickletMotorizedLinearPoti(uid, ipcon)
Parameters:
  • uid – Type: str
  • ipcon – Type: IPConnection
Returns:
  • motorized_linear_poti – Type: BrickletMotorizedLinearPoti

Creates an object with the unique device ID uid:

motorized_linear_poti = BrickletMotorizedLinearPoti("YOUR_DEVICE_UID", ipcon)

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

BrickletMotorizedLinearPoti.get_position()
Returns:
  • position – Type: int, Range: [0 to 100]

Returns the position of the linear potentiometer. The value is between 0 (slider down) and 100 (slider up).

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

BrickletMotorizedLinearPoti.set_motor_position(position, drive_mode, hold_position)
Parameters:
  • position – Type: int, Range: [0 to 100]
  • drive_mode – Type: int, Range: See constants
  • hold_position – Type: bool
Returns:
  • None

Sets the position of the potentiometer. The motorized potentiometer will immediately start to approach the position. Depending on the chosen drive mode, the position will either be reached as fast as possible or in a slow but smooth motion.

The position has to be between 0 (slider down) and 100 (slider up).

If you set the hold position parameter to true, the position will automatically be retained. If a user changes the position of the potentiometer, it will automatically drive back to the original set point.

If the hold position parameter is set to false, the potentiometer can be changed again by the user as soon as the set point was reached once.

The following constants are available for this function:

For drive_mode:

  • BrickletMotorizedLinearPoti.DRIVE_MODE_FAST = 0
  • BrickletMotorizedLinearPoti.DRIVE_MODE_SMOOTH = 1
BrickletMotorizedLinearPoti.get_motor_position()
Return Object:
  • position – Type: int, Range: [0 to 100]
  • drive_mode – Type: int, Range: See constants
  • hold_position – Type: bool
  • position_reached – Type: bool

Returns the last motor position as set by set_motor_position(). This is not the current position (use get_position() to get the current position). This is the last used set point and configuration.

The position reached parameter is true if the position has been reached at one point. The position may have been changed again in the meantime by the user.

The following constants are available for this function:

For drive_mode:

  • BrickletMotorizedLinearPoti.DRIVE_MODE_FAST = 0
  • BrickletMotorizedLinearPoti.DRIVE_MODE_SMOOTH = 1

Advanced Functions

BrickletMotorizedLinearPoti.calibrate()
Returns:
  • None

Starts a calibration procedure. The potentiometer will be driven to the extreme points to calibrate the potentiometer.

The calibration is saved in flash, it does not have to be called on every start up.

The Motorized Linear Poti Bricklet is already factory-calibrated during testing at Tinkerforge.

BrickletMotorizedLinearPoti.get_spitfp_error_count()
Return Object:
  • error_count_ack_checksum – Type: int, Range: [0 to 232 - 1]
  • error_count_message_checksum – Type: int, Range: [0 to 232 - 1]
  • error_count_frame – Type: int, Range: [0 to 232 - 1]
  • error_count_overflow – Type: int, Range: [0 to 232 - 1]

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.

BrickletMotorizedLinearPoti.set_bootloader_mode(mode)
Parameters:
  • mode – Type: int, Range: See constants
Returns:
  • status – Type: int, Range: See constants

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:

For mode:

  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4

For status:

  • BrickletMotorizedLinearPoti.BOOTLOADER_STATUS_OK = 0
  • BrickletMotorizedLinearPoti.BOOTLOADER_STATUS_INVALID_MODE = 1
  • BrickletMotorizedLinearPoti.BOOTLOADER_STATUS_NO_CHANGE = 2
  • BrickletMotorizedLinearPoti.BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • BrickletMotorizedLinearPoti.BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • BrickletMotorizedLinearPoti.BOOTLOADER_STATUS_CRC_MISMATCH = 5
BrickletMotorizedLinearPoti.get_bootloader_mode()
Returns:
  • mode – Type: int, Range: See constants

Returns the current bootloader mode, see set_bootloader_mode().

The following constants are available for this function:

For mode:

  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletMotorizedLinearPoti.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
BrickletMotorizedLinearPoti.set_write_firmware_pointer(pointer)
Parameters:
  • pointer – Type: int, Unit: 1 B, Range: [0 to 232 - 1]
Returns:
  • 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.

BrickletMotorizedLinearPoti.write_firmware(data)
Parameters:
  • data – Type: [int, ...], Length: 64, Range: [0 to 255]
Returns:
  • status – Type: int, Range: [0 to 255]

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.

BrickletMotorizedLinearPoti.set_status_led_config(config)
Parameters:
  • config – Type: int, Range: See constants, Default: 3
Returns:
  • 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:

For config:

  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_OFF = 0
  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_ON = 1
  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_SHOW_STATUS = 3
BrickletMotorizedLinearPoti.get_status_led_config()
Returns:
  • config – Type: int, Range: See constants, Default: 3

Returns the configuration as set by set_status_led_config()

The following constants are available for this function:

For config:

  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_OFF = 0
  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_ON = 1
  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletMotorizedLinearPoti.STATUS_LED_CONFIG_SHOW_STATUS = 3
BrickletMotorizedLinearPoti.get_chip_temperature()
Returns:
  • temperature – Type: int, Unit: 1 °C, Range: [-215 to 215 - 1]

Returns the temperature 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.

BrickletMotorizedLinearPoti.reset()
Returns:
  • 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!

BrickletMotorizedLinearPoti.write_uid(uid)
Parameters:
  • uid – Type: int, Range: [0 to 232 - 1]
Returns:
  • 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.

BrickletMotorizedLinearPoti.read_uid()
Returns:
  • uid – Type: int, Range: [0 to 232 - 1]

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

BrickletMotorizedLinearPoti.get_identity()
Return Object:
  • uid – Type: str, Length: up to 8
  • connected_uid – Type: str, Length: up to 8
  • position – Type: chr, Range: ["a" to "h", "i", "z"]
  • hardware_version – Type: [int, ...], Length: 3
    • 0: major – Type: int, Range: [0 to 255]
    • 1: minor – Type: int, Range: [0 to 255]
    • 2: revision – Type: int, Range: [0 to 255]
  • firmware_version – Type: [int, ...], Length: 3
    • 0: major – Type: int, Range: [0 to 255]
    • 1: minor – Type: int, Range: [0 to 255]
    • 2: revision – Type: int, Range: [0 to 255]
  • device_identifier – Type: int, Range: [0 to 216 - 1]

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). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

BrickletMotorizedLinearPoti.register_callback(callback_id, function)
Parameters:
  • callback_id – Type: int
  • function – Type: callable
Returns:
  • None

Registers the given function with the given callback_id.

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

BrickletMotorizedLinearPoti.set_position_callback_configuration(period, value_has_to_change, option, min, max)
Parameters:
  • period – Type: int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • value_has_to_change – Type: bool, Default: False
  • option – Type: chr, Range: See constants, Default: "x"
  • min – Type: int, Range: [0 to 216 - 1], Default: 0
  • max – Type: int, Range: [0 to 216 - 1], Default: 0
Returns:
  • None

The period is the period with which the CALLBACK_POSITION 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.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the CALLBACK_POSITION callback.

The following options are possible:

Option Description
'x' Threshold is turned off
'o' Threshold is triggered when the value is outside the min and max values
'i' Threshold is triggered when the value is inside or equal to the min and max values
'<' Threshold is triggered when the value is smaller than the min value (max is ignored)
'>' Threshold is triggered when the value is greater than the min value (max is ignored)

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

The following constants are available for this function:

For option:

  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_OFF = "x"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_GREATER = ">"
BrickletMotorizedLinearPoti.get_position_callback_configuration()
Return Object:
  • period – Type: int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • value_has_to_change – Type: bool, Default: False
  • option – Type: chr, Range: See constants, Default: "x"
  • min – Type: int, Range: [0 to 216 - 1], Default: 0
  • max – Type: int, Range: [0 to 216 - 1], Default: 0

Returns the callback configuration as set by set_position_callback_configuration().

The following constants are available for this function:

For option:

  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_OFF = "x"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletMotorizedLinearPoti.THRESHOLD_OPTION_GREATER = ">"
BrickletMotorizedLinearPoti.set_position_reached_callback_configuration(enabled)
Parameters:
  • enabled – Type: bool, Default: True
Returns:
  • None

Enables/Disables CALLBACK_POSITION_REACHED callback.

BrickletMotorizedLinearPoti.get_position_reached_callback_configuration()
Returns:
  • enabled – Type: bool, Default: True

Returns the CALLBACK_POSITION_REACHED callback configuration as set by set_position_reached_callback_configuration().

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)

motorized_linear_poti.register_callback(BrickletMotorizedLinearPoti.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.

BrickletMotorizedLinearPoti.CALLBACK_POSITION
Callback Parameters:
  • position – Type: int, Range: [0 to 100]

This callback is triggered periodically according to the configuration set by set_position_callback_configuration().

The parameter is the same as get_position().

BrickletMotorizedLinearPoti.CALLBACK_POSITION_REACHED
Callback Parameters:
  • position – Type: int, Range: [0 to 100]

This callback is triggered if a new position as set by set_motor_position() is reached.

The parameter is the current position.

Virtual Functions

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

BrickletMotorizedLinearPoti.get_api_version()
Return Object:
  • api_version – Type: [int, ...], Length: 3
    • 0: major – Type: int, Range: [0 to 255]
    • 1: minor – Type: int, Range: [0 to 255]
    • 2: revision – Type: int, Range: [0 to 255]

Returns the version of the API definition 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.

BrickletMotorizedLinearPoti.get_response_expected(function_id)
Parameters:
  • function_id – Type: int, Range: See constants
Returns:
  • response_expected – 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:

For function_id:

  • BrickletMotorizedLinearPoti.FUNCTION_SET_POSITION_CALLBACK_CONFIGURATION = 2
  • BrickletMotorizedLinearPoti.FUNCTION_SET_MOTOR_POSITION = 5
  • BrickletMotorizedLinearPoti.FUNCTION_CALIBRATE = 7
  • BrickletMotorizedLinearPoti.FUNCTION_SET_POSITION_REACHED_CALLBACK_CONFIGURATION = 8
  • BrickletMotorizedLinearPoti.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletMotorizedLinearPoti.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletMotorizedLinearPoti.FUNCTION_RESET = 243
  • BrickletMotorizedLinearPoti.FUNCTION_WRITE_UID = 248
BrickletMotorizedLinearPoti.set_response_expected(function_id, response_expected)
Parameters:
  • function_id – Type: int, Range: See constants
  • response_expected – Type: bool
Returns:
  • 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:

For function_id:

  • BrickletMotorizedLinearPoti.FUNCTION_SET_POSITION_CALLBACK_CONFIGURATION = 2
  • BrickletMotorizedLinearPoti.FUNCTION_SET_MOTOR_POSITION = 5
  • BrickletMotorizedLinearPoti.FUNCTION_CALIBRATE = 7
  • BrickletMotorizedLinearPoti.FUNCTION_SET_POSITION_REACHED_CALLBACK_CONFIGURATION = 8
  • BrickletMotorizedLinearPoti.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletMotorizedLinearPoti.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletMotorizedLinearPoti.FUNCTION_RESET = 243
  • BrickletMotorizedLinearPoti.FUNCTION_WRITE_UID = 248
BrickletMotorizedLinearPoti.set_response_expected_all(response_expected)
Parameters:
  • response_expected – Type: bool
Returns:
  • None

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

Constants

BrickletMotorizedLinearPoti.DEVICE_IDENTIFIER

This constant is used to identify a Motorized Linear Poti Bricklet.

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.

BrickletMotorizedLinearPoti.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Motorized Linear Poti Bricklet.