[Lazarus] USB Commincation with Lazarus and libusb library

[Henry Vermaak]

> Hi,
>
> in response to your message :
>
> I have install the libusb library on my MAC OS X and I have link libusb with my Lazrus project and I can call function.
>
> The problem is when I try do dev := dev^.next; or dev^.descriptor.idVendor = $04d8 or another operation on dev I get an error
> "EXC_ACCESS_ERROR"
> Is it an memory problem ?

make sure you have sufficient rights to access the usb device (run
your program as root to test).  i have no idea how to give this access
on the mac, but you use udev for this on linux.

i see in your sources that you don't try and open the device or claim
an interface.  try and do this before you check vid/pid:  like so:

while bus <> nil do begin
    dev := bus^.devices;
    while dev <> nil do begin
          usb_device := usb_open(dev);
          if (usb_device <> nil) and ((dev^.descriptor.idVendor =
$1234) and (dev^.descriptor.idProduct = $4568)) then ...

i'm not sure if it will solve your problem, though.

if this doesn't help, try the testlibusb.c program in the usb sources
and see if that works.

henry