Perl - Joystick Bricklet

This is the description of the Perl API bindings for the Joystick Bricklet. General information and technical specifications for the Joystick 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::BrickletJoystick;

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

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

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

# Get current position
my ($x, $y) = $j->get_position();

print "Position [X]: $x\n";
print "Position [Y]: $y\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::BrickletJoystick;

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

# Callback subroutine for pressed callback
sub cb_pressed
{
    print "Pressed\n";
}

# Callback subroutine for released callback
sub cb_released
{
    print "Released\n";
}

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

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

# Register pressed callback to subroutine cb_pressed
$j->register_callback($j->CALLBACK_PRESSED, 'cb_pressed');

# Register released callback to subroutine cb_released
$j->register_callback($j->CALLBACK_RELEASED, 'cb_released');

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

Find Borders

Download (example_find_borders.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickletJoystick;

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

# Callback subroutine for position reached callback
sub cb_position_reached
{
    my ($x, $y) = @_;

    if ($y == 100)
    {
        print "Top\n";
    }
    elsif ($y == -100)
    {
        print "Bottom\n";
    }

    if ($x == 100)
    {
        print "Right\n";
    }
    elsif ($x == -100)
    {
        print "Left\n";
    }

    print "\n";
}

my $ipcon = Tinkerforge::IPConnection->new(); # Create IP connection
my $j = Tinkerforge::BrickletJoystick->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 0.2 seconds (200ms)
$j->set_debounce_period(200);

# Register position reached callback to subroutine cb_position_reached
$j->register_callback($j->CALLBACK_POSITION_REACHED, 'cb_position_reached');

# Configure threshold for position "outside of -99, -99 to 99, 99"
$j->set_position_callback_threshold('o', -99, 99, -99, 99);

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

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

BrickletJoystick

Creates an object with the unique device ID $uid:

$joystick = BrickletJoystick->new("YOUR_DEVICE_UID", $ipcon);

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

BrickletJoystick->get_position()
Return type:[int, int]

Returns the position of the Joystick. The value ranges between -100 and 100 for both axis. The middle position of the joystick is x=0, y=0. The returned values are averaged and calibrated (see calibrate()).

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().

The returned array contains the elements x and y.

BrickletJoystick->is_pressed()
Return type:bool

Returns true if the button is pressed and false otherwise.

It is recommended to use the CALLBACK_PRESSED and CALLBACK_RELEASED callbacks to handle the button.

Advanced Functions

BrickletJoystick->get_analog_value()
Return type:[int, int]

Returns the values as read by a 12-bit analog-to-digital converter. The values are between 0 and 4095 for both axis.

Note

The values returned by get_position() are 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 values periodically, it is recommended to use the CALLBACK_ANALOG_VALUE callback and set the period with set_analog_value_callback_period().

The returned array contains the elements x and y.

BrickletJoystick->calibrate()
Return type:undef

Calibrates the middle position of the Joystick. If your Joystick Bricklet does not return x=0 and y=0 in the middle position, call this function while the Joystick is standing still in the middle position.

The resulting calibration will be saved on the EEPROM of the Joystick Bricklet, thus you only have to calibrate it once.

BrickletJoystick->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.

BrickletJoystick->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.

BrickletJoystick->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:

  • BrickletJoystick->FUNCTION_CALIBRATE = 4
  • BrickletJoystick->FUNCTION_SET_POSITION_CALLBACK_PERIOD = 5
  • BrickletJoystick->FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 7
  • BrickletJoystick->FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 9
  • BrickletJoystick->FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 11
  • BrickletJoystick->FUNCTION_SET_DEBOUNCE_PERIOD = 13
BrickletJoystick->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.

BrickletJoystick->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

BrickletJoystick->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.

BrickletJoystick->set_position_callback_period($period)
Parameters:$period -- int
Return type:undef

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.

BrickletJoystick->get_position_callback_period()
Return type:int

Returns the period as set by set_position_callback_period().

BrickletJoystick->set_analog_value_callback_period($period)
Parameters:$period -- int
Return type:undef

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 values have changed since the last triggering.

The default value is 0.

BrickletJoystick->get_analog_value_callback_period()
Return type:int

Returns the period as set by set_analog_value_callback_period().

BrickletJoystick->set_position_callback_threshold($option, $min_x, $max_x, $min_y, $max_y)
Parameters:
  • $option -- char
  • $min_x -- int
  • $max_x -- int
  • $min_y -- int
  • $max_y -- int
Return type:

undef

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 values (max is ignored)
'>' Callback is triggered when the position is greater than the min values (max is ignored)

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

The following constants are available for this function:

  • BrickletJoystick->THRESHOLD_OPTION_OFF = 'x'
  • BrickletJoystick->THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletJoystick->THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletJoystick->THRESHOLD_OPTION_SMALLER = '<'
  • BrickletJoystick->THRESHOLD_OPTION_GREATER = '>'
BrickletJoystick->get_position_callback_threshold()
Return type:[char, int, int, int, int]

Returns the threshold as set by set_position_callback_threshold().

The following constants are available for this function:

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

The returned array contains the elements option, min_x, max_x, min_y and max_y.

BrickletJoystick->set_analog_value_callback_threshold($option, $min_x, $max_x, $min_y, $max_y)
Parameters:
  • $option -- char
  • $min_x -- int
  • $max_x -- int
  • $min_y -- int
  • $max_y -- int
Return type:

undef

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 values are outside the min and max values
'i' Callback is triggered when the analog values are inside the min and max values
'<' Callback is triggered when the analog values are smaller than the min values (max is ignored)
'>' Callback is triggered when the analog values are greater than the min values (max is ignored)

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

The following constants are available for this function:

  • BrickletJoystick->THRESHOLD_OPTION_OFF = 'x'
  • BrickletJoystick->THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletJoystick->THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletJoystick->THRESHOLD_OPTION_SMALLER = '<'
  • BrickletJoystick->THRESHOLD_OPTION_GREATER = '>'
BrickletJoystick->get_analog_value_callback_threshold()
Return type:[char, int, int, int, int]

Returns the threshold as set by set_analog_value_callback_threshold().

The following constants are available for this function:

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

The returned array contains the elements option, min_x, max_x, min_y and max_y.

BrickletJoystick->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.

BrickletJoystick->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]";
}

$joystick->register_callback(BrickletJoystick->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.

BrickletJoystick->CALLBACK_POSITION
Parameters:
  • $x -- int
  • $y -- int

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

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

BrickletJoystick->CALLBACK_ANALOG_VALUE
Parameters:
  • $x -- int
  • $y -- int

This callback is triggered periodically with the period that is set by set_analog_value_callback_period(). The parameters are the analog values of the Joystick.

The CALLBACK_ANALOG_VALUE callback is only triggered if the values have changed since the last triggering.

BrickletJoystick->CALLBACK_POSITION_REACHED
Parameters:
  • $x -- int
  • $y -- int

This callback is triggered when the threshold as set by set_position_callback_threshold() is reached. The parameters are the position of the Joystick.

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

BrickletJoystick->CALLBACK_ANALOG_VALUE_REACHED
Parameters:
  • $x -- int
  • $y -- int

This callback is triggered when the threshold as set by set_analog_value_callback_threshold() is reached. The parameters are the analog values of the Joystick.

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

BrickletJoystick->CALLBACK_PRESSED

This callback is triggered when the button is pressed.

BrickletJoystick->CALLBACK_RELEASED

This callback is triggered when the button is released.

Constants

BrickletJoystick->DEVICE_IDENTIFIER

This constant is used to identify a Joystick 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.

BrickletJoystick->DEVICE_DISPLAY_NAME

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