Software / API Bindings / Python / API Reference and Examples / Bricklets / Linear Poti Bricklet

Python - Linear Poti Bricklet¶

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

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

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Linear Poti Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_linear_poti import BrickletLinearPoti

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

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

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

    input("Press key to exit\n") # Use raw_input() in Python 2
    ipcon.disconnect()

Callback¶

Download (example_callback.py)

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

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Linear Poti Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_linear_poti import BrickletLinearPoti

# 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
    lp = BrickletLinearPoti(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
    lp.register_callback(lp.CALLBACK_POSITION, cb_position)

    # Set period for position callback to 0.05s (50ms)
    # Note: The position callback is only called every 0.05 seconds
    #       if the position has changed since the last call!
    lp.set_position_callback_period(50)

    input("Press key to exit\n") # Use raw_input() in Python 2
    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
Error.WRONG_DEVICE_TYPE = -15
Error.DEVICE_REPLACED = -16
Error.WRONG_RESPONSE_LENGTH = -17

All functions listed below are thread-safe.

Basic Functions¶

BrickletLinearPoti(uid, ipcon)¶

Parameters:	uid – Type: str ipcon – Type: IPConnection
Returns:	linear_poti – Type: BrickletLinearPoti

Creates an object with the unique device ID uid:

linear_poti = BrickletLinearPoti("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected.

BrickletLinearPoti.get_position()¶

Returns:	position – Type: int, Unit: 1 %, 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 position periodically, it is recommended to use the CALLBACK_POSITION callback and set the period with set_position_callback_period().

Advanced Functions¶

BrickletLinearPoti.get_analog_value()¶

Returns:	value – Type: int, Range: [0 to 2¹² - 1]

Returns the value as read by a 12-bit analog-to-digital converter.

Note

The value returned by get_position() is averaged over several samples to yield less noise, while get_analog_value() gives back raw unfiltered analog values. The only reason to use get_analog_value() is, if you need the full resolution of the analog-to-digital converter.

If you want the analog value periodically, it is recommended to use the CALLBACK_ANALOG_VALUE callback and set the period with set_analog_value_callback_period().

BrickletLinearPoti.get_identity()¶

Return Object:

Return Object:	uid – Type: str, Length: up to 8 connected_uid – Type: str, Length: up to 8 position – Type: chr, Range: ["a" to "h", "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]

uid – Type: str, Length: up to 8
connected_uid – Type: str, Length: up to 8
position – Type: chr, Range: ["a" to "h", "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). A Bricklet connected to an Isolator Bricklet is always at 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¶

BrickletLinearPoti.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.

BrickletLinearPoti.set_position_callback_period(period)¶

Parameters:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	None

Sets the period with which the CALLBACK_POSITION callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_POSITION callback is only triggered if the position has changed since the last triggering.

BrickletLinearPoti.get_position_callback_period()¶

Returns:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by set_position_callback_period().

BrickletLinearPoti.set_analog_value_callback_period(period)¶

Parameters:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	None

Sets the period with which the CALLBACK_ANALOG_VALUE callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_ANALOG_VALUE callback is only triggered if the analog value has changed since the last triggering.

BrickletLinearPoti.get_analog_value_callback_period()¶

Returns:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by set_analog_value_callback_period().

BrickletLinearPoti.set_position_callback_threshold(option, min, max)¶

Parameters:	option – Type: chr, Range: See constants, Default: "x" min – Type: int, Unit: 1 %, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: int, Unit: 1 %, Range: [0 to 2¹⁶ - 1], Default: 0
Returns:	None

Sets the thresholds for the CALLBACK_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 value (max is ignored)
'>'	Callback is triggered when the position is greater than the min value (max is ignored)

The following constants are available for this function:

For option:

BrickletLinearPoti.THRESHOLD_OPTION_OFF = "x"
BrickletLinearPoti.THRESHOLD_OPTION_OUTSIDE = "o"
BrickletLinearPoti.THRESHOLD_OPTION_INSIDE = "i"
BrickletLinearPoti.THRESHOLD_OPTION_SMALLER = "<"
BrickletLinearPoti.THRESHOLD_OPTION_GREATER = ">"

BrickletLinearPoti.get_position_callback_threshold()¶

Return Object:	option – Type: chr, Range: See constants, Default: "x" min – Type: int, Unit: 1 %, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: int, Unit: 1 %, Range: [0 to 2¹⁶ - 1], Default: 0

Returns the threshold as set by set_position_callback_threshold().

The following constants are available for this function:

For option:

BrickletLinearPoti.THRESHOLD_OPTION_OFF = "x"
BrickletLinearPoti.THRESHOLD_OPTION_OUTSIDE = "o"
BrickletLinearPoti.THRESHOLD_OPTION_INSIDE = "i"
BrickletLinearPoti.THRESHOLD_OPTION_SMALLER = "<"
BrickletLinearPoti.THRESHOLD_OPTION_GREATER = ">"

BrickletLinearPoti.set_analog_value_callback_threshold(option, min, max)¶

Parameters:	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

Sets the thresholds for the CALLBACK_ANALOG_VALUE_REACHED callback.

The following options are possible:

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

The following constants are available for this function:

For option:

BrickletLinearPoti.THRESHOLD_OPTION_OFF = "x"
BrickletLinearPoti.THRESHOLD_OPTION_OUTSIDE = "o"
BrickletLinearPoti.THRESHOLD_OPTION_INSIDE = "i"
BrickletLinearPoti.THRESHOLD_OPTION_SMALLER = "<"
BrickletLinearPoti.THRESHOLD_OPTION_GREATER = ">"

BrickletLinearPoti.get_analog_value_callback_threshold()¶

Return Object:	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 threshold as set by set_analog_value_callback_threshold().

The following constants are available for this function:

For option:

BrickletLinearPoti.THRESHOLD_OPTION_OFF = "x"
BrickletLinearPoti.THRESHOLD_OPTION_OUTSIDE = "o"
BrickletLinearPoti.THRESHOLD_OPTION_INSIDE = "i"
BrickletLinearPoti.THRESHOLD_OPTION_SMALLER = "<"
BrickletLinearPoti.THRESHOLD_OPTION_GREATER = ">"

BrickletLinearPoti.set_debounce_period(debounce)¶

Parameters:	debounce – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100
Returns:	None

Sets the period with which the threshold callbacks

CALLBACK_POSITION_REACHED,
CALLBACK_ANALOG_VALUE_REACHED

are triggered, if the thresholds

set_position_callback_threshold(),
set_analog_value_callback_threshold()

keep being reached.

BrickletLinearPoti.get_debounce_period()¶

Returns:	debounce – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100

Returns the debounce period as set by set_debounce_period().

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)

linear_poti.register_callback(BrickletLinearPoti.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.

BrickletLinearPoti.CALLBACK_POSITION¶

Callback Parameters:	position – Type: int, Unit: 1 %, Range: [0 to 100]

This callback is triggered periodically with the period that is set by set_position_callback_period(). The parameter is the position of the linear potentiometer.

The CALLBACK_POSITION callback is only triggered if the position has changed since the last triggering.

BrickletLinearPoti.CALLBACK_ANALOG_VALUE¶

Callback Parameters:	value – Type: int, Range: [0 to 2¹² - 1]

This callback is triggered periodically with the period that is set by set_analog_value_callback_period(). The parameter is the analog value of the Linear Potentiometer.

The CALLBACK_ANALOG_VALUE callback is only triggered if the position has changed since the last triggering.

BrickletLinearPoti.CALLBACK_POSITION_REACHED¶

Callback Parameters:	position – Type: int, Unit: 1 %, Range: [0 to 100]

This callback is triggered when the threshold as set by set_position_callback_threshold() is reached. The parameter is the position of the linear potentiometer.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period().

BrickletLinearPoti.CALLBACK_ANALOG_VALUE_REACHED¶

Callback Parameters:	value – Type: int, Range: [0 to 2¹² - 1]

This callback is triggered when the threshold as set by set_analog_value_callback_threshold() is reached. The parameter is the analog value of the linear potentiometer.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period().

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.

BrickletLinearPoti.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.

BrickletLinearPoti.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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

BrickletLinearPoti.FUNCTION_SET_POSITION_CALLBACK_PERIOD = 3
BrickletLinearPoti.FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 5
BrickletLinearPoti.FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 7
BrickletLinearPoti.FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 9
BrickletLinearPoti.FUNCTION_SET_DEBOUNCE_PERIOD = 11

BrickletLinearPoti.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.

The following constants are available for this function:

For function_id:

BrickletLinearPoti.FUNCTION_SET_POSITION_CALLBACK_PERIOD = 3
BrickletLinearPoti.FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 5
BrickletLinearPoti.FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 7
BrickletLinearPoti.FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 9
BrickletLinearPoti.FUNCTION_SET_DEBOUNCE_PERIOD = 11

BrickletLinearPoti.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¶

BrickletLinearPoti.DEVICE_IDENTIFIER¶

This constant is used to identify a 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.

BrickletLinearPoti.DEVICE_DISPLAY_NAME¶: This constant represents the human readable name of a Linear Poti Bricklet.