[libusb] using libusb with multiple endpoints

[ALAN B. <adb...@bt...>]

Dear All,

Up to now, I've been working with an embedded device that was ennumerating as a simple libusb device in Windows' device manager. I was then able to write a C++ application based on the libusb library to receive bulk packets from my device.

My project requirements have changed on me and my embedded device is now ennumerating as a composite device with a virtual COM port and 2 instances of a simple libusb device. As expected I can see a VCOM, a USB composite device and 2 libusb "USB serial bus devices" in Windows device manager.

I've been able to check that the VCOM interface works OK using tera term. I've tried to modify my libusb based PC application (by changing the interface number and endpoints) to communicate with my embedded device but I get the following errors:

Device Opened
libusb: error [parse_endpoint] invalid extra ep desc len (0)
libusb: error [raw_desc_to_config] parse_configuration failed with error -1
libusb: warning [windows_assign_endpoints] could not read config descriptor: error -1
Cannot Claim Interface
Cannot Release Interface

Is this a limitation of libusb? Is the libusb library unable to use multiple endpoints? 

Thanks in advance for your advice,

Regards,

Alan