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Open 2 USB HID devices

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TZ2002

Open 2 USB HID devices

Hi,
I'm trying to Open 2 USB HID devices with the same Prod ID and Vendor ID
SN is different off course .
I'm getting 2 devices on the list , but I always seem to open the same device
I see it by a function to get the device SN .

part of the code :

HIDInterface* hid;
struct usb_bus *usb_bus;
struct usb_device *dev;
usb_init();
usb_find_busses();
usb_find_devices();
HIDInterfaceMatcher matcher = { VENDOR_ID, PRODUCT_ID, NULL, NULL, 0 };
for (usb_bus = usb_busses; usb_bus; usb_bus = usb_bus->next) // 2 devices are available
{
for (dev = usb_bus->devices; dev; dev = dev->next)
{
if ((dev->descriptor.idVendor == VENDOR_ID) &&
(dev->descriptor.idProduct == PRODUCT_ID))
{
ret = hid_init();
hid1 = hid_new_HIDInterface();
ret = hid_force_open(hid, 0, &matcher, 3);
Get_SN(SNreceive,hid); // a function to retrieve the device SN
}
}
}

any idea?

thanks
T.Z

Tim Roberts

Re: Open 2 USB HID devices

TZ2002 wrote:
> I'm trying to Open 2 USB HID devices with the same Prod ID and Vendor ID
> SN is different off course .
> I'm getting 2 devices on the list , but I always seem to open the same
> device

That's not your exact code; you have a confusion between "hid" and
"hid1" as the names of the structure.

Also, this is a libhid question, not a libusb question.

hid_force_open does its own search. It opens the first match it finds
that is not already open. Thus, there is no point in having you loop
through the devices -- let libhid do it. So, this should work:

hid_init();
hid1 = hid_new_HIDInterface();
hid_force_open( hid1, 0, &matcher, 3 );
hid2 = hid_new_HIDInterface();
hid_force_open( hid2, 0, &matcher, 3 );

--
Tim Roberts, [hidden email]
Providenza & Boekelheide, Inc.

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TZ2002

Re: Open 2 USB HID devices

Tim Roberts wrote

TZ2002 wrote:
> I'm trying to Open 2 USB HID devices with the same Prod ID and Vendor ID
> SN is different off course .
> I'm getting 2 devices on the list , but I always seem to open the same
> device

That's not your exact code; you have a confusion between "hid" and
"hid1" as the names of the structure.

Also, this is a libhid question, not a libusb question.

hid_force_open does its own search. It opens the first match it finds
that is not already open. Thus, there is no point in having you loop
through the devices -- let libhid do it. So, this should work:

hid_init();
hid1 = hid_new_HIDInterface();
hid_force_open( hid1, 0, &matcher, 3 );
hid2 = hid_new_HIDInterface();
hid_force_open( hid2, 0, &matcher, 3 );

--
Tim Roberts, [hidden email]
Providenza & Boekelheide, Inc.

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Thanks,
What you suggest is not working -So I will check libhid.

Alan Ott

Re: Open 2 USB HID devices

In reply to this post by TZ2002

On 06/11/2012 06:08 AM, TZ2002 wrote:

> Hi,
> I'm trying to Open 2 USB HID devices with the same Prod ID and Vendor ID
> SN is different off course .
> I'm getting 2 devices on the list , but I always seem to open the same
> device
> I see it by a function to get the device SN .
>
> part of the code :
>
> HIDInterface* hid;
> struct usb_bus *usb_bus;
> struct usb_device *dev;
> usb_init();
> usb_find_busses();
> usb_find_devices();
> HIDInterfaceMatcher matcher = { VENDOR_ID, PRODUCT_ID, NULL, NULL, 0 };
> for (usb_bus = usb_busses; usb_bus; usb_bus = usb_bus->next) // 2
> devices are available
> {
> for (dev = usb_bus->devices; dev; dev = dev->next)
> {
> if ((dev->descriptor.idVendor == VENDOR_ID) &&
> (dev->descriptor.idProduct == PRODUCT_ID))
> {
> ret = hid_init();
> hid1 = hid_new_HIDInterface();
> ret = hid_force_open(hid, 0, &matcher, 3);
> Get_SN(SNreceive,hid); // a function to retrieve the device
> SN
> }
> }
> }
>
>
> any idea?

You may want to take a look at HIDAPI [1]. Libhid is based on the
long-deprecated libusb-0.1 (at least according to the current website).

Opening devices based on serial number is a use case that was designed
into HIDAPI from the start.

Judge for yourself though; I'm biased :)

Alan.

[1] http://www.signal11.us/oss/hidapi/

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Exclusive live event will cover all the ways today's security and
threat landscape has changed and how IT managers can respond. Discussions
will include endpoint security, mobile security and the latest in malware
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
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