Perl - Multi Touch Bricklet

This is the description of the Perl API bindings for the Multi Touch Bricklet. General information and technical specifications for the Multi Touch 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::BrickletMultiTouch;

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

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

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

# Get current touch state
my $state = $mt->get_touch_state();
my $s = '';
my $left_shift_1_12_bits = (1 << 12);

if (($state) & ($left_shift_1_12_bits))
{
    $s .= 'In proximity, ';
}

if (($state & 0xfff) == 0)
{
    $s .= 'No electrodes touched';
}
else
{
    $s .= 'Electrodes ';

    for (my $i = 0; $i < 12; $i++)
    {
        my $left_shift_1_i_bits = 1 << $i;

        if ($state & $left_shift_1_i_bits)
        {
            $s .= "$i ";
        }
    }

    $s .= 'touched';
}

print "$s\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::BrickletMultiTouch;

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

# Callback subroutine for touch state callback
sub cb_touch_state
{
    my ($state) = @_;

    my $s = '';
    my $left_shift_1_12_bits = (1 << 12);

    if (($state) & ($left_shift_1_12_bits))
    {
        $s .= 'In proximity, ';
    }

    if (($state & 0xfff) == 0)
    {
        $s .= 'No electrodes touched';
    }
    else
    {
        $s .= 'Electrodes ';

        for (my $i = 0; $i < 12; $i++)
        {
            my $left_shift_1_i_bits = 1 << $i;

            if ($state & $left_shift_1_i_bits)
            {
                $s .= "$i ";
            }
        }

        $s .= 'touched';
    }

    print "$s\n";
}

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

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

# Register touch state callback to subroutine cb_touch_state
$mt->register_callback($mt->CALLBACK_TOUCH_STATE, 'cb_touch_state');

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

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

BrickletMultiTouch

Creates an object with the unique device ID $uid:

$multi_touch = BrickletMultiTouch->new("YOUR_DEVICE_UID", $ipcon);

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

BrickletMultiTouch->get_touch_state()
Return type:int

Returns the current touch state. The state is given as a bitfield.

Bits 0 to 11 represent the 12 electrodes and bit 12 represents the proximity.

If an electrode is touched, the corresponding bit is true. If a hand or similar is in proximity to the electrodes, bit 12 is true.

Example: The state 4103 = 0x1007 = 0b1000000000111 means that electrodes 0, 1 and 2 are touched and that something is in the proximity of the electrodes.

The proximity is activated with a distance of 1-2cm. An electrode is already counted as touched if a finger is nearly touching the electrode. This means that you can put a piece of paper or foil or similar on top of a electrode to build a touch panel with a professional look.

BrickletMultiTouch->recalibrate()
Return type:undef

Recalibrates the electrodes. Call this function whenever you changed or moved you electrodes.

BrickletMultiTouch->set_electrode_config($enabled_electrodes)
Parameters:$enabled_electrodes -- int
Return type:undef

Enables/disables electrodes with a bitfield (see get_touch_state()).

True enables the electrode, false disables the electrode. A disabled electrode will always return false as its state. If you don't need all electrodes you can disable the electrodes that are not needed.

It is recommended that you disable the proximity bit (bit 12) if the proximity feature is not needed. This will reduce the amount of traffic that is produced by the CALLBACK_TOUCH_STATE callback.

Disabling electrodes will also reduce power consumption.

Default: 8191 = 0x1FFF = 0b1111111111111 (all electrodes enabled)

BrickletMultiTouch->get_electrode_config()
Return type:int

Returns the electrode configuration, as set by set_electrode_config().

BrickletMultiTouch->set_electrode_sensitivity($sensitivity)
Parameters:$sensitivity -- int
Return type:undef

Sets the sensitivity of the electrodes. An electrode with a high sensitivity will register a touch earlier then an electrode with a low sensitivity.

If you build a big electrode you might need to decrease the sensitivity, since the area that can be charged will get bigger. If you want to be able to activate an electrode from further away you need to increase the sensitivity.

After a new sensitivity is set, you likely want to call recalibrate() to calibrate the electrodes with the newly defined sensitivity.

The valid sensitivity value range is 5-201.

The default sensitivity value is 181.

BrickletMultiTouch->get_electrode_sensitivity()
Return type:int

Returns the current sensitivity, as set by set_electrode_sensitivity().

Advanced Functions

BrickletMultiTouch->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.

BrickletMultiTouch->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.

BrickletMultiTouch->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:

  • BrickletMultiTouch->FUNCTION_RECALIBRATE = 2
  • BrickletMultiTouch->FUNCTION_SET_ELECTRODE_CONFIG = 3
  • BrickletMultiTouch->FUNCTION_SET_ELECTRODE_SENSITIVITY = 6
BrickletMultiTouch->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.

BrickletMultiTouch->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

BrickletMultiTouch->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]";
}

$multi_touch->register_callback(BrickletMultiTouch->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.

BrickletMultiTouch->CALLBACK_TOUCH_STATE
Parameters:$state -- int

Returns the current touch state, see get_touch_state() for information about the state.

This callback is triggered every time the touch state changes.

Constants

BrickletMultiTouch->DEVICE_IDENTIFIER

This constant is used to identify a Multi Touch 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.

BrickletMultiTouch->DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Multi Touch Bricklet.