Brandon Fosdick > USB-Descriptor-4 > USB::Descriptor

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NAME ^

USB::Descriptor - USB Device Descriptor generation tools

SYNOPSIS ^

A set of classes and methods for generating USB descriptor sets.

    use USB::Descriptor;

    my $device = USB::Descriptor::device( product => 'My First Device' );
    $device->vendorID(0x1234);
    $device->productID(0x5678);
    $device->configurations( [ USB::Descriptor::Configuration->new() ] );
    ...

DESCRIPTION ^

USB::Descriptor provides a means of specifying a device's USB descriptors and then generating descriptor structures suitable for use in the device's firmware. However, USB::Descriptor only generates the bytes that comprise the structures, it does not handle generation of valid source code.

Any strings used in the descriptor set are automatically assigned indexes and collected into a set of string descriptors by the top level USB::Descriptor::Device object.

The easiest way to create a new descriptor set is to use the USB::Descriptor::device() factory method. It accepts a hash of arguments that happens to be the same hash expected by USB::Descriptor::Device and returns a reference to a new USB::Descriptor::Device object.

    use USB::Descriptor;

    my $device = USB::Descriptor::device(
        'usb_version'       => '2.0.0',         # Default
        'max_packet_size'   => 64,              # Full speed device
        'vendorID'          => 0x1234,
        'productID'         => 0x5678,
        'manufacturer'      => 'Acme, Inc.',
        'product'           => 'Giant Catapult',
        'serial_number'     => '007',
        'configurations'    => [{
            'description'   => 'Configuration 0',
            'remote_wakeup'     => 1,
            'max_current'       => 100,   # mA
            'interfaces'        => [{
                'description'       => 'Interface 0',
                'endpoints'         => [{
                    'direction'         => 'in',
                    'number'            => 1,
                    'max_packet_size'   => 42,
                }],
            }],
        },
    );

The code above generates a USB::Descriptor::Device object as well as a USB::Descriptor::Configuration, a USB::Descriptor::Interface and a single USB::Descriptor::Endpoint. Each descriptor object is configured using the provided arguments and added to the descriptor tree.

Values for the device descriptor structure can be obtained by calling $device->bytes, or by using arrayification ( @{$device} ).

    my @bytes = $device->bytes

or

    my @bytes = @{$device};

A simple script can then be written to emit the device descriptor structure in whatever language is appropriate to the device's project. For example, to store the descriptor as an array of bytes for a C language project...

    print "uint8_t device_descriptor[] = {", join(', ', @bytes), "};\n";

Calling bytes on a USB::Descriptor::Configuration object, or arrayifying it, produces a similar result. However, the configuration object returns more than a configuration descriptor worth of values. It returns the concatenated set of configuration, interface and endpoint descriptors that is requested by a USB host during device enumeration. Generating suitable C source might be accomplished with:

    my @configurations = @{$device->configurations};
    foreach my $configuration ( @configurations )
    {
        print 'uint8_t configuration[] = {',
                join(', ', @{$configuration->bytes} ), "}\n";
    }

When calling bytes, or arrayifying a USB::Descriptor::Device, all of the child objects are queried for their strings. The resulting strings are automatically assigned string indexes and assembled into a string descriptor set. The set of assembled strings can be retrieved as an array, in index order, by calling $device->strings. The first string in the array is the string that should be returned by the device in response to a request for string ID 1.

    my @strings = $device->strings

Suitable language-specific code can then be generated from the resulting array of strings.

CLASS METHODS ^

$device = USB::Descriptor::composite(vendorID=>$vendorID, ...);

Convience method for creating descriptors for Composite devices.

Constructs and returns a new USB::Descriptor::Device object using the passed options and sets class, subclass, and protocol to zero. Each option key is the name of an accessor method of USB::Descriptor::Device.

$device = USB::Descriptor::device(vendorID=>$vendorID, ...);

Constructs and returns a new USB::Descriptor::Device object using the passed options. Each option key is the name of an accessor method of USB::Descriptor::Device.

AUTHOR ^

Brandon Fosdick, <bfoz at bfoz.net>

BUGS ^

Please report any bugs or feature requests to bug-usb-descriptor at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=USB-Descriptor. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT ^

You can find documentation for this module with the perldoc command.

    perldoc USB::Descriptor

You can also look for information at:

ACKNOWLEDGEMENTS ^

LICENSE AND COPYRIGHT ^

Copyright 2011 Brandon Fosdick.

This program is released under the terms of the BSD License.

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