I am trying to connect to a USB device plugged into my Ubuntu linux system. The command set is a set of 64 bytes with the first byte as the command. Command 0x02 is a version cmd and doesn't require any other information so the rest of the bytes can be 0x00. From the documents Bulk interface 4 ep7=IN ep8=OUT. It should send info (64bytes) which will contain the version.

I am getting a -22 error when reading or writing and not sure what I am doing wrong. Any assistance is appreciated.

(Note: when printing the endpoint out address I am getting bEndpointAddress of 8), bulk_write needs (endpoint, bytes, timeout)

#!/usr/bin/perl
use Device::USB;
use Data::Dumper;
$idV = 0x0432; # VendorID  changed to protect the innocent
$idP = 0x4321; # productID changed to protect the innocent

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

if (!defined $dev) {
    print "Unable to find device \n";
    exit;
}
$dev->open();

$driver = $dev->get_driver_np(0); 
if (defined $driver) {
    print "connected to driver ($driver), releasing\n";
    $res = $dev->detach_kernel_driver_np(0);
}

$res = $dev->claim_interface(0);
if ($res == 0) {
    print "device claimed\n";
}

$dev->set_configuration(1);

my $cfg = $dev->config()->[0];

my $inter = $cfg->interfaces()->[4];
#epi=endpoint in, epo=endpoint out
if (!defined $inter) { print "inter not defined\n"; }
my $epi = $inter->[0]->endpoints()->[0];
my $epo = $inter->[0]->endpoints()->[1];


# string of hex values in pairs i.e. 02 00 00, 64 entries
# cmd string is 0x02 followed by all 0x00
$mybuff = '02000000000000000000000000000000000000000000000000000000000
+000000000000000000000000000000000000000000000000000000000000000000000
+';
# convert string to bytestring
my @hex   = ($mybuff =~ /(..)/g); #grab pairs into @hex 02 00 etc
my @dec   = map { hex($_) } @dec; # convert to decimal
my @byteArr = map { pack('C', $_) } @hex; # pack into bytearray
my $bs = pack("b", @byteArr);  #push back into a byte string format

print "calling bulk_write\n";
$bWritten = $dev->bulk_write($epo, $bs, 5000); 
print "bWritten=($bWritten)\n";
my $readInfo;
print "calling bulk_read\n";
$bRead = $dev->bulk_read($epi, $readInfo, 64, 5000);
print "bRead=($bRead)\n";
print "readInfo=($readInfo)\n"; 

print "release interface 0\n";
$res = $dev->release_interface(0);
print "claim release result = ($res)\n";
[download]

connected to driver (snd-usb-audio), releasing
device claimed
calling bulk_write
bWritten=(-22)
calling bulk_read
bRead=(-22)
readInfo=()
release interface 0
claim release result = (0)
[download]

[2509634.708198] usb 2-1.7.7.2: usbfs: interface 0 claimed by usbfs wh
+ile 'perl' sets config #1
[download]