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Manual Reference Pages  -  DEVICE::USB::DEVICE (3)

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Device::USB::Device

This class encapsulates the USB device structure and the methods that may be applied to it.

CONTENTS

NAME

Device::USB::Device - Use libusb to access USB devices.

VERSION

Version 0.29

SYNOPSIS

Device:USB::Device provides a Perl object for accessing a USB device using the libusb library.



    use Device::USB;

    my $usb = Device::USB->new();
    my $dev = $usb->find_device( $VENDOR, $PRODUCT );

    printf "Device: %04X:%04X\n", $dev->idVendor(), $dev->idProduct();
    print "Manufactured by ", $dev->manufacturer(), "\n",
          " Product: ", $dev->product(), "\n";

    $dev->set_configuration( $CFG );
    $dev->control_msg( @params );
    ...



See the libusb manual for more information about most of the methods. The functionality is generally the same as the libusb function whose name is the method name prepended with usb_.

DESCRIPTION

This module defines a Perl object that represents the data and functionality associated with a USB device. The object interface provides read-only access to the important data associated with a device. It also provides methods for almost all of the functions supplied by libusb. Where necessary, the interfaces to these methods were changed to better match Perl usage. However, most of the methods are straight-forward wrappers around their libusb counterparts.

    METHODS

DESTROY Close the device connected to the object.
filename Retrieve the filename associated with the device.
config In list context, return a list of the configuration structures for this device. In scalar context, return a reference to that list. This method is deprecated in favor of the two new methods: configurations and get_configuration.
configurations In list context, return a list of the configuration structures for this device. In scalar context, return a reference to that list.
get_configuration Retrieve the configuration requested by index. The legal values are from 0 to bNumConfigurations() - 1. Negative values access from the back of the list of configurations.
index numeric index of the index to return. If not supplied, use 0.

Returns an object encapsulating the configuration on success, or undef on failure.

accessors There a several accessor methods that return data from the device and device descriptor. Each is named after the field that they return. All of the BCD fields have been changed to floating point numbers, so that you don’t have to decode them yourself.

The methods include:
bcdUSB
bDeviceClass
bDeviceSubClass
bDeviceProtocol
bMaxPacketSize0
idVendor
idProduct
bcdDevice
iManufacturer
iProduct
iSerialNumber
bNumConfigurations

manufacturer Retrieve the manufacture name from the device as a string. Return undef if the device read fails.
product Retrieve the product name from the device as a string. Return undef if the device read fails.
serial_number Retrieve the serial number from the device as a string. Return undef if the device read fails.
open Open the device. If the device is already open, close it and reopen it.

If the device fails to open, the reason will be available in $!.

set_configuration Sets the active configuration of the device.
configuration the integer specified in the descriptor field bConfigurationValue.

returns 0 on success or <0 on error

When using libusb-win32 under Windows, it is important to call set_configuration() after the open() but before any other method calls. Without this call, other methods may not work. This call is not required under Linux.

set_altinterface Sets the active alternative setting of the current interface for the device.
alternate the integer specified in the descriptor field bAlternateSetting.

returns 0 on success or <0 on error

clear_halt Clears any halt status on the supplied endpoint.
alternate the integer specified bEndpointAddress descriptor field.

returns 0 on success or <0 on error

reset Resets the device. This also closes the handle and invalidates this device. This device will be unusable.
claim_interface Claims the specified interface with the operating system.
interface The interface value listed in the descriptor field bInterfaceNumber.

Returns 0 on success, <0 on failure.

release_interface Releases the specified interface back to the operating system.
interface The interface value listed in the descriptor field bInterfaceNumber.

Returns 0 on success, <0 on failure.

control_msg Performs a control request to the default control pipe on a device.
requesttype
request
value
index
bytes Any returned data is placed here. If you don’t want any returned data, pass undef.
size Size of supplied buffer.
timeout Milliseconds to wait for response.

Returns number of bytes read or written on success, <0 on failure.

get_string Retrieve a string descriptor from the device.
index The index of the string in the string list.
langid The language id used to specify which of the supported languages the string should be encoded in.

Returns a Unicode string. The function returns undef on error.

get_string_simple Retrieve a string descriptor from the device.
index The index of the string in the string list.

Returns a C-style string if successful, or undef on error.

get_descriptor Retrieve a descriptor from the device
type The type of descriptor to retrieve.
index The index of that descriptor in the list of descriptors of that type.

TODO: This method needs major rewrite to be Perl-ish. I need to provide a better way to specify the type (or at least document which are available), and I need to return a Perl data structure, not a buffer of binary data.

get_descriptor_by_endpoint Retrieve an endpoint-specific descriptor from the device
ep Endpoint to query.
type The type of descriptor to retrieve.
index The index of that descriptor in the list of descriptors.
buf Buffer into which to write the requested descriptor
size Max size to read into the buffer.

TODO: This method needs major rewrite to be Perl-ish. I need to provide a better way to specify the type (or at least document which are available), and I need to return a Perl data structure, not a buffer of binary data.

bulk_read Perform a bulk read request from the specified endpoint.
ep The number of the endpoint to read
bytes Buffer into which to write the requested data.
size Max size to read into the buffer.
timeout Maximum time to wait (in milliseconds)

The function returns the number of bytes returned or <0 on error.

USB is packet based, not stream based. So using bulk_read() to read part of the packet acts like a peek. The next time you read, all of the packet is still there.

The data is only removed when you read the entire packet. For this reason, you should always call bulk_read() with the total packet size.

interrupt_read Perform a interrupt read request from the specified endpoint.
ep The number of the endpoint to read
bytes Buffer into which to write the requested data.
size Max size to read into the buffer.
timeout Maximum time to wait (in milliseconds)

The function returns the number of bytes returned or <0 on error.

bulk_write Perform a bulk write request to the specified endpoint.
ep The number of the endpoint to write
bytes Buffer from which to write the requested data.
timeout Maximum time to wait (in milliseconds)

The function returns the number of bytes written or <0 on error.

interrupt_write Perform a interrupt write request to the specified endpoint.
ep The number of the endpoint to write
bytes Buffer from which to write the requested data.
timeout Maximum time to wait (in milliseconds)

The function returns the number of bytes written or <0 on error.

get_driver_np This function returns the name of the driver bound to the interface specified by the parameter interface.
$interface The interface number of interest.

Returns undef on error.

detach_kernel_driver_np This function will detach a kernel driver from the interface specified by parameter interface. Applications using libusb can then try claiming the interface. Returns 0 on success or < 0 on error.

DIAGNOSTICS

This is an explanation of the diagnostic and error messages this module can generate.
Cannot open device: reason string Unable to open the USB device for the reason given.

DEPENDENCIES

This module depends on the Carp, Inline and Inline::C modules, as well as the strict and warnings pragmas. Obviously, libusb must be available since that is the entire reason for the module’s existence.

AUTHOR

G. Wade Johnson (wade at anomaly dot org) Paul Archer (paul at paularcher dot org)

Houston Perl Mongers Group

BUGS

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

ACKNOWLEDGEMENTS

Thanks go to various members of the Houston Perl Mongers group for input on the module. But thanks mostly go to Paul Archer who proposed the project and helped with the development.

COPYRIGHT & LICENSE

Copyright 2006 Houston Perl Mongers

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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perl v5.20.3 DEVICE::USB::DEVICE (3) 2009-04-02

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