Su, Yu (Eugene) <> wrote:
> Hi,
>
> I have a DLL from FTDI (ftd2xx.dll www.ftdichip.com) for a USB
> device. I try to write a simple perl script to list a number of (FTD)
> USB devices connected to a PC. My code below got an error on invalid
> parameter;
>
> Argument "M-\0\0\0\0\" isn't numeric in subroutine entry at demo.pl
> line #
>
> I guess I did not pass a hex data in the function call properly. Can
> someone help me?
>
> Thanks.
>
> Eugene
>
> ######## code snippet #######
>
> use strict;
> use Win32::API;
> use Carp;
> use warnings;
>
> # from FTD2xx programmer guide:
> # FT_ListDevices(PVOID numDevs,PVOID NULL,DWORD FT_LIST_NUMBER_ONLY)
> # FT_LIST_NUMBER_ONLY is defined in FTD2xx.h as #define
> FT_LIST_NUMBER_ONLY = 0x80000000 # my $function = new
> Win32::API("ftd2xx", "FT_ListDevices", "PPN", "N"); if (not defined
> $function) { die "Can't import API FT_ListDevices: $!\n"; } my
> $DevBuffer = " " x 80; my $FT_LIST_NUMBER_ONLY=pack('N', 0x80000000);
> my $status=$function->Call($DevBuffer,0,$FT_LIST_NUMBER_ONLY);
> print "status: $status\n";
> print "DeviceNumber: $DevBuffer";
I think that you problem is the 'pack'. Why do you think you need it?.
Just use 0x80000000 in your function call, or if you want to define it
as a constant, 'use constant FT_LIST_NUMBER_ONLY => 0x80000000;' is more
nearly equivalent to the #define you quote, and will add to your codes
readability. For example, you dould write it something like this:
use strict;
use warnings;
use Win32::API;
use constant FT_LIST_NUMBER_ONLY => 0x80000000;
my $function = new Win32::API("ftd2xx", "FT_ListDevices", "PPN", "N");
die "Can't import API FT_ListDevices: $!\n" unless defined $function;
my $DevBuffer = " " x 80;
my $status=$function->Call($DevBuffer, 0 ,FT_LIST_NUMBER_ONLY);
print "status: $status\n";
print "DeviceNumber: $DevBuffer";
HTH
--
Brian Raven
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