Python - Distance IR Bricklet

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

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_distance_ir import BrickletDistanceIR

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

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

    # Get current distance
    distance = dir.get_distance()
    print("Distance: " + str(distance/10.0) + " cm")

    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 Distance IR Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_distance_ir import BrickletDistanceIR

# Callback function for distance callback
def cb_distance(distance):
    print("Distance: " + str(distance/10.0) + " cm")

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

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

    # Register distance callback to function cb_distance
    dir.register_callback(dir.CALLBACK_DISTANCE, cb_distance)

    # Set period for distance callback to 0.2s (200ms)
    # Note: The distance callback is only called every 0.2 seconds
    #       if the distance has changed since the last call!
    dir.set_distance_callback_period(200)

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

Threshold

Download (example_threshold.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 Distance IR Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_distance_ir import BrickletDistanceIR

# Callback function for distance reached callback
def cb_distance_reached(distance):
    print("Distance: " + str(distance/10.0) + " cm")

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

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

    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    dir.set_debounce_period(10000)

    # Register distance reached callback to function cb_distance_reached
    dir.register_callback(dir.CALLBACK_DISTANCE_REACHED, cb_distance_reached)

    # Configure threshold for distance "smaller than 30 cm"
    dir.set_distance_callback_threshold("<", 30*10, 0)

    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

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

Creates an object with the unique device ID uid:

distance_ir = BrickletDistanceIR("YOUR_DEVICE_UID", ipcon)

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

BrickletDistanceIR.get_distance()
Return type:int

Returns the distance measured by the sensor. The value is in mm and possible distance ranges are 40 to 300, 100 to 800 and 200 to 1500, depending on the selected IR sensor.

If you want to get the distance periodically, it is recommended to use the CALLBACK_DISTANCE callback and set the period with set_distance_callback_period().

Advanced Functions

BrickletDistanceIR.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_distance() 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().

BrickletDistanceIR.set_sampling_point(position, distance)
Parameters:
  • position -- int
  • distance -- int
Return type:

None

Sets a sampling point value to a specific position of the lookup table. The lookup table comprises 128 equidistant analog values with corresponding distances.

If you measure a distance of 50cm at the analog value 2048, you should call this function with (64, 5000). The utilized analog-to-digital converter has a resolution of 12 bit. With 128 sampling points on the whole range, this means that every sampling point has a size of 32 analog values. Thus the analog value 2048 has the corresponding sampling point 64 = 2048/32.

Sampling points are saved on the EEPROM of the Distance IR Bricklet and loaded again on startup.

Note

An easy way to calibrate the sampling points of the Distance IR Bricklet is implemented in the Brick Viewer. If you want to calibrate your Bricklet it is highly recommended to use this implementation.

BrickletDistanceIR.get_sampling_point(position)
Parameters:position -- int
Return type:int

Returns the distance to a sampling point position as set by set_sampling_point().

BrickletDistanceIR.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.

BrickletDistanceIR.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.

BrickletDistanceIR.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:

  • BrickletDistanceIR.FUNCTION_SET_SAMPLING_POINT = 3
  • BrickletDistanceIR.FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 5
  • BrickletDistanceIR.FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 7
  • BrickletDistanceIR.FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 9
  • BrickletDistanceIR.FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 11
  • BrickletDistanceIR.FUNCTION_SET_DEBOUNCE_PERIOD = 13
BrickletDistanceIR.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.

BrickletDistanceIR.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

BrickletDistanceIR.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.

BrickletDistanceIR.set_distance_callback_period(period)
Parameters:period -- int
Return type:None

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

The CALLBACK_DISTANCE callback is only triggered if the distance has changed since the last triggering.

The default value is 0.

BrickletDistanceIR.get_distance_callback_period()
Return type:int

Returns the period as set by set_distance_callback_period().

BrickletDistanceIR.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.

BrickletDistanceIR.get_analog_value_callback_period()
Return type:int

Returns the period as set by set_analog_value_callback_period().

BrickletDistanceIR.set_distance_callback_threshold(option, min, max)
Parameters:
  • option -- chr
  • min -- int
  • max -- int
Return type:

None

Sets the thresholds for the CALLBACK_DISTANCE_REACHED callback.

The following options are possible:

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

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

The following constants are available for this function:

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

Returns the threshold as set by set_distance_callback_threshold().

The following constants are available for this function:

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

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

BrickletDistanceIR.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:

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

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

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

BrickletDistanceIR.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.

BrickletDistanceIR.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)

distance_ir.register_callback(BrickletDistanceIR.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.

BrickletDistanceIR.CALLBACK_DISTANCE
Parameters:distance -- int

This callback is triggered periodically with the period that is set by set_distance_callback_period(). The parameter is the distance of the sensor.

The CALLBACK_DISTANCE callback is only triggered if the distance has changed since the last triggering.

BrickletDistanceIR.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 sensor.

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

BrickletDistanceIR.CALLBACK_DISTANCE_REACHED
Parameters:distance -- int

This callback is triggered when the threshold as set by set_distance_callback_threshold() is reached. The parameter is the distance of the sensor.

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

BrickletDistanceIR.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 sensor.

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

Constants

BrickletDistanceIR.DEVICE_IDENTIFIER

This constant is used to identify a Distance IR 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.

BrickletDistanceIR.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Distance IR Bricklet.