Python - Current25 Bricklet

This is the description of the Python API bindings for the Current25 Bricklet. General information and technical specifications for the Current25 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 Current25 Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_current25 import BrickletCurrent25

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    c = BrickletCurrent25(UID, ipcon) # Create device object

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

    # Get current current
    current = c.get_current()
    print("Current: " + str(current/1000.0) + " A")

    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 Current25 Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_current25 import BrickletCurrent25

# Callback function for current callback
def cb_current(current):
    print("Current: " + str(current/1000.0) + " A")

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    c = BrickletCurrent25(UID, ipcon) # Create device object

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

    # Register current callback to function cb_current
    c.register_callback(c.CALLBACK_CURRENT, cb_current)

    # Set period for current callback to 1s (1000ms)
    # Note: The current callback is only called every second
    #       if the current has changed since the last call!
    c.set_current_callback_period(1000)

    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 Current25 Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_current25 import BrickletCurrent25

# Callback function for current reached callback
def cb_current_reached(current):
    print("Current: " + str(current/1000.0) + " A")

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    c = BrickletCurrent25(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)
    c.set_debounce_period(10000)

    # Register current reached callback to function cb_current_reached
    c.register_callback(c.CALLBACK_CURRENT_REACHED, cb_current_reached)

    # Configure threshold for current "greater than 5 A"
    c.set_current_callback_threshold(">", 5*1000, 0)

    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

BrickletCurrent25(uid, ipcon)
Parameters:
  • uid – Type: str
  • ipcon – Type: IPConnection
Returns:
  • current25 – Type: BrickletCurrent25

Creates an object with the unique device ID uid:

current25 = BrickletCurrent25("YOUR_DEVICE_UID", ipcon)

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

BrickletCurrent25.get_current()
Returns:
  • current – Type: int, Unit: 1 mA, Range: [-25000 to 25000]

Returns the current of the sensor.

If you want to get the current periodically, it is recommended to use the CALLBACK_CURRENT callback and set the period with set_current_callback_period().

Advanced Functions

BrickletCurrent25.calibrate()
Returns:
  • None

Calibrates the 0 value of the sensor. You have to call this function when there is no current present.

The zero point of the current sensor is depending on the exact properties of the analog-to-digital converter, the length of the Bricklet cable and the temperature. Thus, if you change the Brick or the environment in which the Bricklet is used, you might have to recalibrate.

The resulting calibration will be saved on the EEPROM of the Current Bricklet.

BrickletCurrent25.is_over_current()
Returns:
  • over – Type: bool

Returns true if more than 25A were measured.

Note

To reset this value you have to power cycle the Bricklet.

BrickletCurrent25.get_analog_value()
Returns:
  • value – Type: int, Range: [0 to 4095]

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

Note

The value returned by get_current() 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().

BrickletCurrent25.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

BrickletCurrent25.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.

BrickletCurrent25.set_current_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_CURRENT callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_CURRENT callback is only triggered if the current has changed since the last triggering.

BrickletCurrent25.get_current_callback_period()
Returns:
  • period – Type: int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by set_current_callback_period().

BrickletCurrent25.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.

BrickletCurrent25.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().

BrickletCurrent25.set_current_callback_threshold(option, min, max)
Parameters:
  • option – Type: chr, Range: See constants, Default: "x"
  • min – Type: int, Unit: 1 mA, Range: [-215 to 215 - 1], Default: 0
  • max – Type: int, Unit: 1 mA, Range: [-215 to 215 - 1], Default: 0
Returns:
  • None

Sets the thresholds for the CALLBACK_CURRENT_REACHED callback.

The following options are possible:

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

The following constants are available for this function:

For option:

  • BrickletCurrent25.THRESHOLD_OPTION_OFF = "x"
  • BrickletCurrent25.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletCurrent25.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletCurrent25.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletCurrent25.THRESHOLD_OPTION_GREATER = ">"
BrickletCurrent25.get_current_callback_threshold()
Return Object:
  • option – Type: chr, Range: See constants, Default: "x"
  • min – Type: int, Unit: 1 mA, Range: [-215 to 215 - 1], Default: 0
  • max – Type: int, Unit: 1 mA, Range: [-215 to 215 - 1], Default: 0

Returns the threshold as set by set_current_callback_threshold().

The following constants are available for this function:

For option:

  • BrickletCurrent25.THRESHOLD_OPTION_OFF = "x"
  • BrickletCurrent25.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletCurrent25.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletCurrent25.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletCurrent25.THRESHOLD_OPTION_GREATER = ">"
BrickletCurrent25.set_analog_value_callback_threshold(option, min, max)
Parameters:
  • option – Type: chr, Range: See constants, Default: "x"
  • min – Type: int, Range: [0 to 4095], Default: 0
  • max – Type: int, Range: [0 to 4095], 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:

  • BrickletCurrent25.THRESHOLD_OPTION_OFF = "x"
  • BrickletCurrent25.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletCurrent25.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletCurrent25.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletCurrent25.THRESHOLD_OPTION_GREATER = ">"
BrickletCurrent25.get_analog_value_callback_threshold()
Return Object:
  • option – Type: chr, Range: See constants, Default: "x"
  • min – Type: int, Range: [0 to 4095], Default: 0
  • max – Type: int, Range: [0 to 4095], Default: 0

Returns the threshold as set by set_analog_value_callback_threshold().

The following constants are available for this function:

For option:

  • BrickletCurrent25.THRESHOLD_OPTION_OFF = "x"
  • BrickletCurrent25.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletCurrent25.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletCurrent25.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletCurrent25.THRESHOLD_OPTION_GREATER = ">"
BrickletCurrent25.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

are triggered, if the thresholds

keep being reached.

BrickletCurrent25.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)

current25.register_callback(BrickletCurrent25.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.

BrickletCurrent25.CALLBACK_CURRENT
Callback Parameters:
  • current – Type: int, Unit: 1 mA, Range: [-25000 to 25000]

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

The CALLBACK_CURRENT callback is only triggered if the current has changed since the last triggering.

BrickletCurrent25.CALLBACK_ANALOG_VALUE
Callback Parameters:
  • value – Type: int, Range: [0 to 4095]

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 current has changed since the last triggering.

BrickletCurrent25.CALLBACK_CURRENT_REACHED
Callback Parameters:
  • current – Type: int, Unit: 1 mA, Range: [-25000 to 25000]

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

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

BrickletCurrent25.CALLBACK_ANALOG_VALUE_REACHED
Callback Parameters:
  • value – Type: int, Range: [0 to 4095]

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().

BrickletCurrent25.CALLBACK_OVER_CURRENT
Callback Parameters:
  • no parameters

This callback is triggered when an over current is measured (see is_over_current()).

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.

BrickletCurrent25.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.

BrickletCurrent25.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:

  • BrickletCurrent25.FUNCTION_CALIBRATE = 2
  • BrickletCurrent25.FUNCTION_SET_CURRENT_CALLBACK_PERIOD = 5
  • BrickletCurrent25.FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 7
  • BrickletCurrent25.FUNCTION_SET_CURRENT_CALLBACK_THRESHOLD = 9
  • BrickletCurrent25.FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 11
  • BrickletCurrent25.FUNCTION_SET_DEBOUNCE_PERIOD = 13
BrickletCurrent25.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:

  • BrickletCurrent25.FUNCTION_CALIBRATE = 2
  • BrickletCurrent25.FUNCTION_SET_CURRENT_CALLBACK_PERIOD = 5
  • BrickletCurrent25.FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 7
  • BrickletCurrent25.FUNCTION_SET_CURRENT_CALLBACK_THRESHOLD = 9
  • BrickletCurrent25.FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 11
  • BrickletCurrent25.FUNCTION_SET_DEBOUNCE_PERIOD = 13
BrickletCurrent25.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

BrickletCurrent25.DEVICE_IDENTIFIER

This constant is used to identify a Current25 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.

BrickletCurrent25.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Current25 Bricklet.