Software / API Bindings / Python / API Reference and Examples / Bricklets / Barometer Bricklet

Python - Barometer Bricklet¶

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

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_barometer import BrickletBarometer

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

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

    # Get current air pressure
    air_pressure = b.get_air_pressure()
    print("Air Pressure: " + str(air_pressure/1000.0) + " hPa")

    # Get current altitude
    altitude = b.get_altitude()
    print("Altitude: " + str(altitude/100.0) + " m")

    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 Barometer Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_barometer import BrickletBarometer

# Callback function for air pressure callback
def cb_air_pressure(air_pressure):
    print("Air Pressure: " + str(air_pressure/1000.0) + " hPa")

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

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

    # Register air pressure callback to function cb_air_pressure
    b.register_callback(b.CALLBACK_AIR_PRESSURE, cb_air_pressure)

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

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

Threshold¶

Download (example_threshold.py)

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

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

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_barometer import BrickletBarometer

# Callback function for air pressure reached callback
def cb_air_pressure_reached(air_pressure):
    print("Air Pressure: " + str(air_pressure/1000.0) + " hPa")
    print("Enjoy the potentially good weather!")

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

    # Register air pressure reached callback to function cb_air_pressure_reached
    b.register_callback(b.CALLBACK_AIR_PRESSURE_REACHED, cb_air_pressure_reached)

    # Configure threshold for air pressure "greater than 1025 hPa"
    b.set_air_pressure_callback_threshold(">", 1025*1000, 0)

    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¶

BrickletBarometer(uid, ipcon)¶

Parameters:	uid – Type: str ipcon – Type: IPConnection
Returns:	barometer – Type: BrickletBarometer

Creates an object with the unique device ID uid:

barometer = BrickletBarometer("YOUR_DEVICE_UID", ipcon)

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

BrickletBarometer.get_air_pressure()¶

Returns:	air_pressure – Type: int, Unit: 1/1000 hPa, Range: [10000 to 1200000]

Returns the air pressure of the air pressure sensor.

If you want to get the air pressure periodically, it is recommended to use the CALLBACK_AIR_PRESSURE callback and set the period with set_air_pressure_callback_period().

BrickletBarometer.get_altitude()¶

Returns:	altitude – Type: int, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]

Returns the relative altitude of the air pressure sensor. The value is calculated based on the difference between the current air pressure and the reference air pressure that can be set with set_reference_air_pressure().

If you want to get the altitude periodically, it is recommended to use the CALLBACK_ALTITUDE callback and set the period with set_altitude_callback_period().

BrickletBarometer.set_reference_air_pressure(air_pressure)¶

Parameters:	air_pressure – Type: int, Unit: 1/1000 hPa, Range: [0, 10000 to 1200000], Default: 1013250
Returns:	None

Sets the reference air pressure for the altitude calculation. Setting the reference to the current air pressure results in a calculated altitude of 0cm. Passing 0 is a shortcut for passing the current air pressure as reference.

Well known reference values are the Q codes QNH and QFE used in aviation.

BrickletBarometer.get_reference_air_pressure()¶

Returns:	air_pressure – Type: int, Unit: 1/1000 hPa, Range: [10000 to 1200000], Default: 1013250

Returns the reference air pressure as set by set_reference_air_pressure().

Advanced Functions¶

BrickletBarometer.get_chip_temperature()¶

Returns:	temperature – Type: int, Unit: 1/100 °C, Range: [-4000 to 8500]

Returns the temperature of the air pressure sensor.

This temperature is used internally for temperature compensation of the air pressure measurement. It is not as accurate as the temperature measured by the Temperature Bricklet or the Temperature IR Bricklet.

BrickletBarometer.set_averaging(moving_average_pressure, average_pressure, average_temperature)¶

Parameters:	moving_average_pressure – Type: int, Range: [0 to 25], Default: 25 average_pressure – Type: int, Range: [0 to 10], Default: 10 average_temperature – Type: int, Range: [0 to 255], Default: 10
Returns:	None

Sets the different averaging parameters. It is possible to set the length of a normal averaging for the temperature and pressure, as well as an additional length of a moving average for the pressure. The moving average is calculated from the normal averages. There is no moving average for the temperature.

Setting the all three parameters to 0 will turn the averaging completely off. If the averaging is off, there is lots of noise on the data, but the data is without delay. Thus we recommend to turn the averaging off if the Barometer Bricklet data is to be used for sensor fusion with other sensors.

New in version 2.0.1 (Plugin).

BrickletBarometer.get_averaging()¶

Return Object:	moving_average_pressure – Type: int, Range: [0 to 25], Default: 25 average_pressure – Type: int, Range: [0 to 10], Default: 10 average_temperature – Type: int, Range: [0 to 255], Default: 10

Returns the averaging configuration as set by set_averaging().

New in version 2.0.1 (Plugin).

BrickletBarometer.set_i2c_mode(mode)¶

Parameters:	mode – Type: int, Range: See constants, Default: 0
Returns:	None

Sets the I2C mode. Possible modes are:

0: Fast (400kHz)
1: Slow (100kHz)

If you have problems with obvious outliers in the Barometer Bricklet measurements, they may be caused by EMI issues. In this case it may be helpful to lower the I2C speed.

It is however not recommended to lower the I2C speed in applications where a high throughput needs to be achieved.

The following constants are available for this function:

For mode:

BrickletBarometer.I2C_MODE_FAST = 0
BrickletBarometer.I2C_MODE_SLOW = 1

New in version 2.0.3 (Plugin).

BrickletBarometer.get_i2c_mode()¶

Returns:	mode – Type: int, Range: See constants, Default: 0

Returns the I2C mode as set by set_i2c_mode().

The following constants are available for this function:

For mode:

BrickletBarometer.I2C_MODE_FAST = 0
BrickletBarometer.I2C_MODE_SLOW = 1

New in version 2.0.3 (Plugin).

BrickletBarometer.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¶

BrickletBarometer.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.

BrickletBarometer.set_air_pressure_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_AIR_PRESSURE callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_AIR_PRESSURE callback is only triggered if the air pressure has changed since the last triggering.

BrickletBarometer.get_air_pressure_callback_period()¶

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

Returns the period as set by set_air_pressure_callback_period().

BrickletBarometer.set_altitude_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_ALTITUDE callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_ALTITUDE callback is only triggered if the altitude has changed since the last triggering.

BrickletBarometer.get_altitude_callback_period()¶

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

Returns the period as set by set_altitude_callback_period().

BrickletBarometer.set_air_pressure_callback_threshold(option, min, max)¶

Parameters:	option – Type: chr, Range: See constants, Default: "x" min – Type: int, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0
Returns:	None

Sets the thresholds for the CALLBACK_AIR_PRESSURE_REACHED callback.

The following options are possible:

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

The following constants are available for this function:

For option:

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

BrickletBarometer.get_air_pressure_callback_threshold()¶

Return Object:	option – Type: chr, Range: See constants, Default: "x" min – Type: int, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0

Returns the threshold as set by set_air_pressure_callback_threshold().

The following constants are available for this function:

For option:

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

BrickletBarometer.set_altitude_callback_threshold(option, min, max)¶

Parameters:	option – Type: chr, Range: See constants, Default: "x" min – Type: int, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0
Returns:	None

Sets the thresholds for the CALLBACK_ALTITUDE_REACHED callback.

The following options are possible:

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

The following constants are available for this function:

For option:

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

BrickletBarometer.get_altitude_callback_threshold()¶

Return Object:	option – Type: chr, Range: See constants, Default: "x" min – Type: int, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0

Returns the threshold as set by set_altitude_callback_threshold().

The following constants are available for this function:

For option:

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

BrickletBarometer.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_AIR_PRESSURE_REACHED,
CALLBACK_ALTITUDE_REACHED

are triggered, if the thresholds

set_air_pressure_callback_threshold(),
set_altitude_callback_threshold()

keep being reached.

BrickletBarometer.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)

barometer.register_callback(BrickletBarometer.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.

BrickletBarometer.CALLBACK_AIR_PRESSURE¶

Callback Parameters:	air_pressure – Type: int, Unit: 1/1000 hPa, Range: [10000 to 1200000]

This callback is triggered periodically with the period that is set by set_air_pressure_callback_period(). The parameter is the air pressure of the air pressure sensor.

The CALLBACK_AIR_PRESSURE callback is only triggered if the air pressure has changed since the last triggering.

BrickletBarometer.CALLBACK_ALTITUDE¶

Callback Parameters:	altitude – Type: int, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]

This callback is triggered periodically with the period that is set by set_altitude_callback_period(). The parameter is the altitude of the air pressure sensor.

The CALLBACK_ALTITUDE callback is only triggered if the altitude has changed since the last triggering.

BrickletBarometer.CALLBACK_AIR_PRESSURE_REACHED¶

Callback Parameters:	air_pressure – Type: int, Unit: 1/1000 hPa, Range: [10000 to 1200000]

This callback is triggered when the threshold as set by set_air_pressure_callback_threshold() is reached. The parameter is the air pressure of the air pressure sensor.

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

BrickletBarometer.CALLBACK_ALTITUDE_REACHED¶

Callback Parameters:	altitude – Type: int, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]

This callback is triggered when the threshold as set by set_altitude_callback_threshold() is reached. The parameter is the altitude of the air pressure sensor.

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.

BrickletBarometer.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.

BrickletBarometer.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:

BrickletBarometer.FUNCTION_SET_AIR_PRESSURE_CALLBACK_PERIOD = 3
BrickletBarometer.FUNCTION_SET_ALTITUDE_CALLBACK_PERIOD = 5
BrickletBarometer.FUNCTION_SET_AIR_PRESSURE_CALLBACK_THRESHOLD = 7
BrickletBarometer.FUNCTION_SET_ALTITUDE_CALLBACK_THRESHOLD = 9
BrickletBarometer.FUNCTION_SET_DEBOUNCE_PERIOD = 11
BrickletBarometer.FUNCTION_SET_REFERENCE_AIR_PRESSURE = 13
BrickletBarometer.FUNCTION_SET_AVERAGING = 20
BrickletBarometer.FUNCTION_SET_I2C_MODE = 22

BrickletBarometer.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:

BrickletBarometer.FUNCTION_SET_AIR_PRESSURE_CALLBACK_PERIOD = 3
BrickletBarometer.FUNCTION_SET_ALTITUDE_CALLBACK_PERIOD = 5
BrickletBarometer.FUNCTION_SET_AIR_PRESSURE_CALLBACK_THRESHOLD = 7
BrickletBarometer.FUNCTION_SET_ALTITUDE_CALLBACK_THRESHOLD = 9
BrickletBarometer.FUNCTION_SET_DEBOUNCE_PERIOD = 11
BrickletBarometer.FUNCTION_SET_REFERENCE_AIR_PRESSURE = 13
BrickletBarometer.FUNCTION_SET_AVERAGING = 20
BrickletBarometer.FUNCTION_SET_I2C_MODE = 22

BrickletBarometer.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¶

BrickletBarometer.DEVICE_IDENTIFIER¶

This constant is used to identify a Barometer 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.

BrickletBarometer.DEVICE_DISPLAY_NAME¶: This constant represents the human readable name of a Barometer Bricklet.