Python - Rotary Poti Bricklet

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

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_rotary_poti import BrickletRotaryPoti

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

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

    # Get current position
    position = rp.get_position()
    print("Position: " + str(position)) # Range: -150 to 150

    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 Rotary Poti Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_rotary_poti import BrickletRotaryPoti

# Callback function for position callback
def cb_position(position):
    print("Position: " + str(position)) # Range: -150 to 150

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    rp = BrickletRotaryPoti(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
    rp.register_callback(rp.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!
    rp.set_position_callback_period(50)

    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.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

All methods listed below are thread-safe.

Basic Functions

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

Creates an object with the unique device ID uid:

rotary_poti = BrickletRotaryPoti("YOUR_DEVICE_UID", ipcon)

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

BrickletRotaryPoti.get_position()
Return type:int

Returns the position of the rotary potentiometer. The value is in degree and between -150° (turned left) and 150° (turned right).

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

BrickletRotaryPoti.get_analog_value()
Return type:int

Returns the value as read by a 12-bit analog-to-digital converter. The value is between 0 and 4095.

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().

BrickletRotaryPoti.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.

BrickletRotaryPoti.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.

See set_response_expected() for the list of function ID constants available for this function.

BrickletRotaryPoti.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 function ID constants are available for this function:

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

BrickletRotaryPoti.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

BrickletRotaryPoti.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.

BrickletRotaryPoti.set_position_callback_period(period)
Parameters:period -- int
Return type:None

Sets the period in ms 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.

The default value is 0.

BrickletRotaryPoti.get_position_callback_period()
Return type:int

Returns the period as set by set_position_callback_period().

BrickletRotaryPoti.set_analog_value_callback_period(period)
Parameters:period -- int
Return type:None

Sets the period in ms 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.

The default value is 0.

BrickletRotaryPoti.get_analog_value_callback_period()
Return type:int

Returns the period as set by set_analog_value_callback_period().

BrickletRotaryPoti.set_position_callback_threshold(option, min, max)
Parameters:
  • option -- chr
  • min -- int
  • max -- int
Return type:

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 default value is ('x', 0, 0).

The following constants are available for this function:

  • BrickletRotaryPoti.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryPoti.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryPoti.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryPoti.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryPoti.THRESHOLD_OPTION_GREATER = '>'
BrickletRotaryPoti.get_position_callback_threshold()
Return type:(chr, int, int)

Returns the threshold as set by set_position_callback_threshold().

The following constants are available for this function:

  • BrickletRotaryPoti.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryPoti.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryPoti.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryPoti.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryPoti.THRESHOLD_OPTION_GREATER = '>'

The returned namedtuple has the variables option, min and max.

BrickletRotaryPoti.set_analog_value_callback_threshold(option, min, max)
Parameters:
  • option -- chr
  • min -- int
  • max -- int
Return type:

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 default value is ('x', 0, 0).

The following constants are available for this function:

  • BrickletRotaryPoti.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryPoti.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryPoti.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryPoti.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryPoti.THRESHOLD_OPTION_GREATER = '>'
BrickletRotaryPoti.get_analog_value_callback_threshold()
Return type:(chr, int, int)

Returns the threshold as set by set_analog_value_callback_threshold().

The following constants are available for this function:

  • BrickletRotaryPoti.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryPoti.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryPoti.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryPoti.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryPoti.THRESHOLD_OPTION_GREATER = '>'

The returned namedtuple has the variables option, min and max.

BrickletRotaryPoti.set_debounce_period(debounce)
Parameters:debounce -- int
Return type:None

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

BrickletRotaryPoti.get_debounce_period()
Return type:int

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)

rotary_poti.register_callback(BrickletRotaryPoti.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.

BrickletRotaryPoti.CALLBACK_POSITION
Parameters:position -- int

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

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

BrickletRotaryPoti.CALLBACK_ANALOG_VALUE
Parameters:value -- int

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 rotary potentiometer.

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

BrickletRotaryPoti.CALLBACK_POSITION_REACHED
Parameters:position -- int

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

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

BrickletRotaryPoti.CALLBACK_ANALOG_VALUE_REACHED
Parameters:value -- int

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 rotary potentiometer.

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

Constants

BrickletRotaryPoti.DEVICE_IDENTIFIER

This constant is used to identify a Rotary Poti 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.

BrickletRotaryPoti.DEVICE_DISPLAY_NAME

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