Perl - Barometer Bricklet

This is the description of the Perl 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 Perl API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example_simple.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickletBarometer;

use constant HOST => 'localhost';
use constant PORT => 4223;
use constant UID => 'XYZ'; # Change XYZ to the UID of your Barometer Bricklet

my $ipcon = Tinkerforge::IPConnection->new(); # Create IP connection
my $b = Tinkerforge::BrickletBarometer->new(&UID, $ipcon); # Create device object

$ipcon->connect(&HOST, &PORT); # Connect to brickd
# Don't use device before ipcon is connected

# Get current air pressure
my $air_pressure = $b->get_air_pressure();
print "Air Pressure: " . $air_pressure/1000.0 . " mbar\n";

# Get current altitude
my $altitude = $b->get_altitude();
print "Altitude: " . $altitude/100.0 . " m\n";

print "Press key to exit\n";
<STDIN>;
$ipcon->disconnect();

Callback

Download (example_callback.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickletBarometer;

use constant HOST => 'localhost';
use constant PORT => 4223;
use constant UID => 'XYZ'; # Change XYZ to the UID of your Barometer Bricklet

# Callback subroutine for air pressure callback
sub cb_air_pressure
{
    my ($air_pressure) = @_;

    print "Air Pressure: " . $air_pressure/1000.0 . " mbar\n";
}

my $ipcon = Tinkerforge::IPConnection->new(); # Create IP connection
my $b = Tinkerforge::BrickletBarometer->new(&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 subroutine 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);

print "Press key to exit\n";
<STDIN>;
$ipcon->disconnect();

Threshold

Download (example_threshold.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickletBarometer;

use constant HOST => 'localhost';
use constant PORT => 4223;
use constant UID => 'XYZ'; # Change XYZ to the UID of your Barometer Bricklet

# Callback subroutine for air pressure reached callback
sub cb_air_pressure_reached
{
    my ($air_pressure) = @_;

    print "Air Pressure: " . $air_pressure/1000.0 . " mbar\n";
    print "Enjoy the potentially good weather!\n";
}

my $ipcon = Tinkerforge::IPConnection->new(); # Create IP connection
my $b = Tinkerforge::BrickletBarometer->new(&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 subroutine cb_air_pressure_reached
$b->register_callback($b->CALLBACK_AIR_PRESSURE_REACHED, 'cb_air_pressure_reached');

# Configure threshold for air pressure "greater than 1025 mbar"
$b->set_air_pressure_callback_threshold('>', 1025*1000, 0);

print "Press key to exit\n";
<STDIN>;
$ipcon->disconnect();

API

Generally, every subroutine of the Perl bindings can report an error as Tinkerforge::Error object via croak(). The object has a get_code() and a get_message() subroutine. There are different error code:

  • Error->ALREADY_CONNECTED = 11
  • Error->NOT_CONNECTED = 12
  • Error->CONNECT_FAILED = 13
  • Error->INVALID_FUNCTION_ID = 21
  • Error->TIMEOUT = 31
  • Error->INVALID_PARAMETER = 41
  • Error->FUNCTION_NOT_SUPPORTED = 42
  • Error->UNKNOWN_ERROR = 43

All methods listed below are thread-safe.

Basic Functions

BrickletBarometer->new($uid, $ipcon)
Parameters:
  • $uid -- string
  • $ipcon -- IPConnection
Return type:

BrickletBarometer

Creates an object with the unique device ID $uid:

$barometer = BrickletBarometer->new("YOUR_DEVICE_UID", $ipcon);

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

BrickletBarometer->get_air_pressure()
Return type:int

Returns the air pressure of the air pressure sensor. The value has a range of 10000 to 1200000 and is given in mbar/1000, i.e. a value of 1001092 means that an air pressure of 1001.092 mbar is measured.

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()
Return type:int

Returns the relative altitude of the air pressure sensor. The value is given in cm and 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 -- int
Return type:undef

Sets the reference air pressure in mbar/1000 for the altitude calculation. Valid values are between 10000 and 1200000. 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.

The default value is 1013.25mbar.

BrickletBarometer->get_reference_air_pressure()
Return type:int

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

Advanced Functions

BrickletBarometer->get_chip_temperature()
Return type:int

Returns the temperature of the air pressure sensor. The value has a range of -4000 to 8500 and is given in °C/100, i.e. a value of 2007 means that a temperature of 20.07 °C is measured.

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 -- int
  • $average_pressure -- int
  • $average_temperature -- int
Return type:

undef

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.

The maximum length for the pressure average is 10, for the temperature average is 255 and for the moving average is 25.

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.

The default values are 10 for the normal averages and 25 for the moving average.

New in version 2.0.1 (Plugin).

BrickletBarometer->get_averaging()
Return type:[int, int, int]

Returns the averaging configuration as set by set_averaging().

New in version 2.0.1 (Plugin).

The returned array contains the elements moving_average_pressure, average_pressure and average_temperature.

BrickletBarometer->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.

BrickletBarometer->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.

BrickletBarometer->set_response_expected($function_id, $response_expected)
Parameters:
  • $function_id -- int
  • $response_expected -- bool
Return type:

undef

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:

  • 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->set_response_expected_all($response_expected)
Parameters:$response_expected -- bool
Return type:undef

Changes the response expected flag for all setter and callback configuration functions of this device at once.

BrickletBarometer->get_identity()
Return type:[string, string, char, [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 array contains the elements uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

BrickletBarometer->register_callback($id, $callback)
Parameters:
  • $id -- int
  • $callback -- string
Return type:

undef

Registers the given $function name 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 -- int
Return type:undef

Sets the period in ms 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.

The default value is 0.

BrickletBarometer->get_air_pressure_callback_period()
Return type:int

Returns the period as set by set_air_pressure_callback_period().

BrickletBarometer->set_altitude_callback_period($period)
Parameters:$period -- int
Return type:undef

Sets the period in ms 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.

The default value is 0.

BrickletBarometer->get_altitude_callback_period()
Return type:int

Returns the period as set by set_altitude_callback_period().

BrickletBarometer->set_air_pressure_callback_threshold($option, $min, $max)
Parameters:
  • $option -- char
  • $min -- int
  • $max -- int
Return type:

undef

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

The following constants are available for this function:

  • 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 type:[char, int, int]

Returns the threshold as set by set_air_pressure_callback_threshold().

The following constants are available for this function:

  • BrickletBarometer->THRESHOLD_OPTION_OFF = 'x'
  • BrickletBarometer->THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletBarometer->THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletBarometer->THRESHOLD_OPTION_SMALLER = '<'
  • BrickletBarometer->THRESHOLD_OPTION_GREATER = '>'

The returned array contains the elements option, min and max.

BrickletBarometer->set_altitude_callback_threshold($option, $min, $max)
Parameters:
  • $option -- char
  • $min -- int
  • $max -- int
Return type:

undef

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

The following constants are available for this function:

  • 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 type:[char, int, int]

Returns the threshold as set by set_altitude_callback_threshold().

The following constants are available for this function:

  • BrickletBarometer->THRESHOLD_OPTION_OFF = 'x'
  • BrickletBarometer->THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletBarometer->THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletBarometer->THRESHOLD_OPTION_SMALLER = '<'
  • BrickletBarometer->THRESHOLD_OPTION_GREATER = '>'

The returned array contains the elements option, min and max.

BrickletBarometer->set_debounce_period($debounce)
Parameters:$debounce -- int
Return type:undef

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

BrickletBarometer->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 name:

sub my_callback
{
    print "@_[0]";
}

$barometer->register_callback(BrickletBarometer->CALLBACK_EXAMPLE, 'my_callback')

The callback function will be called from an internal thread of the IP Connection. In contrast to many other programming languages, variables are not automatically shared between threads in Perl. If you want to share a global variable between a callback function and the rest for your program it has to be marked as :shared. See the documentation of the threads::shared Perl module for more details.

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
Parameters:$air_pressure -- int

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
Parameters:$altitude -- int

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
Parameters:$air_pressure -- int

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
Parameters:$altitude -- int

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().

Constants

BrickletBarometer->DEVICE_IDENTIFIER

This constant is used to identify a Barometer 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.

BrickletBarometer->DEVICE_DISPLAY_NAME

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