Perl - Dual Button Bricklet

This is the description of the Perl API bindings for the Dual Button Bricklet. General information and technical specifications for the Dual Button 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).

Callback

Download (example_callback.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickletDualButton;

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

# Callback subroutine for state changed callback
sub cb_state_changed
{
    my ($button_l, $button_r, $led_l, $led_r) = @_;

    if ($button_l == Tinkerforge::BrickletDualButton->BUTTON_STATE_PRESSED)
    {
        print "Left Button: Pressed\n";
    }
    elsif ($button_l == Tinkerforge::BrickletDualButton->BUTTON_STATE_RELEASED)
    {
        print "Left Button: Released\n";
    }

    if ($button_r == Tinkerforge::BrickletDualButton->BUTTON_STATE_PRESSED)
    {
        print "Right Button: Pressed\n";
    }
    elsif ($button_r == Tinkerforge::BrickletDualButton->BUTTON_STATE_RELEASED)
    {
        print "Right Button: Released\n";
    }

    print "\n";
}

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

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

# Register state changed callback to subroutine cb_state_changed
$db->register_callback($db->CALLBACK_STATE_CHANGED, 'cb_state_changed');

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

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

BrickletDualButton

Creates an object with the unique device ID $uid:

$dual_button = BrickletDualButton->new("YOUR_DEVICE_UID", $ipcon);

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

BrickletDualButton->set_led_state($led_l, $led_r)
Parameters:
  • $led_l -- int
  • $led_r -- int
Return type:

undef

Sets the state of the LEDs. Possible states are:

  • 0 = AutoToggleOn: Enables auto toggle with initially enabled LED.
  • 1 = AutoToggleOff: Activates auto toggle with initially disabled LED.
  • 2 = On: Enables LED (auto toggle is disabled).
  • 3 = Off: Disables LED (auto toggle is disabled).

In auto toggle mode the LED is toggled automatically at each press of a button.

If you just want to set one of the LEDs and don't know the current state of the other LED, you can get the state with get_led_state() or you can use set_selected_led_state().

The default value is (1, 1).

The following constants are available for this function:

  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton->LED_STATE_ON = 2
  • BrickletDualButton->LED_STATE_OFF = 3
BrickletDualButton->get_led_state()
Return type:[int, int]

Returns the current state of the LEDs, as set by set_led_state().

The following constants are available for this function:

  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton->LED_STATE_ON = 2
  • BrickletDualButton->LED_STATE_OFF = 3

The returned array contains the elements led_l and led_r.

BrickletDualButton->get_button_state()
Return type:[int, int]

Returns the current state for both buttons. Possible states are:

  • 0 = pressed
  • 1 = released

The following constants are available for this function:

  • BrickletDualButton->BUTTON_STATE_PRESSED = 0
  • BrickletDualButton->BUTTON_STATE_RELEASED = 1

The returned array contains the elements button_l and button_r.

Advanced Functions

BrickletDualButton->set_selected_led_state($led, $state)
Parameters:
  • $led -- int
  • $state -- int
Return type:

undef

Sets the state of the selected LED (0 or 1).

The other LED remains untouched.

The following constants are available for this function:

  • BrickletDualButton->LED_LEFT = 0
  • BrickletDualButton->LED_RIGHT = 1
  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton->LED_STATE_ON = 2
  • BrickletDualButton->LED_STATE_OFF = 3
BrickletDualButton->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.

BrickletDualButton->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.

BrickletDualButton->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:

  • BrickletDualButton->FUNCTION_SET_LED_STATE = 1
  • BrickletDualButton->FUNCTION_SET_SELECTED_LED_STATE = 5
BrickletDualButton->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.

BrickletDualButton->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

BrickletDualButton->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.

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]";
}

$dual_button->register_callback(BrickletDualButton->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.

BrickletDualButton->CALLBACK_STATE_CHANGED
Parameters:
  • $button_l -- int
  • $button_r -- int
  • $led_l -- int
  • $led_r -- int

This callback is called whenever a button is pressed.

Possible states for buttons are:

  • 0 = pressed
  • 1 = released

Possible states for LEDs are:

  • 0 = AutoToggleOn: Auto toggle enabled and LED on.
  • 1 = AutoToggleOff: Auto toggle enabled and LED off.
  • 2 = On: LED on (auto toggle is disabled).
  • 3 = Off: LED off (auto toggle is disabled).

The following constants are available for this function:

  • BrickletDualButton->BUTTON_STATE_PRESSED = 0
  • BrickletDualButton->BUTTON_STATE_RELEASED = 1
  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton->LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton->LED_STATE_ON = 2
  • BrickletDualButton->LED_STATE_OFF = 3

Constants

BrickletDualButton->DEVICE_IDENTIFIER

This constant is used to identify a Dual Button 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.

BrickletDualButton->DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Dual Button Bricklet.