Posted by Roberto61 on 2016-04-18 23:48

Sorry to be very long and dispersive.
I read the USB port with a c simple test code with the following result:

bus/device idVendor/idProduct
002/004 0483/3748

- Manufacturer : STMicroelectronics
- Product : STM32 STLink
- Serial Number: 0672FF515456707067072452

wTotalLength: 39
bNumInterfaces: 1
bConfigurationValue: 1
iConfiguration: 0
bmAttributes: 80h
MaxPower: 50
bInterfaceNumber: 0
bAlternateSetting: 0
bNumEndpoints: 3
bInterfaceClass: 255
bInterfaceSubClass: 255
bInterfaceProtocol: 255
iInterface: 4
bEndpointAddress: 81h
bmAttributes: 02h
wMaxPacketSize: 64
bInterval: 0
bRefresh: 0
bSynchAddress: 0
bEndpointAddress: 02h
bmAttributes: 02h
wMaxPacketSize: 64
bInterval: 0
bRefresh: 0
bSynchAddress: 0
bEndpointAddress: 83h
bmAttributes: 02h
wMaxPacketSize: 64
bInterval: 0
bRefresh: 0
bSynchAddress: 0

this means that all the permissions are right and the function usb_open(dev) works fine.
Now I really do not know what else to try.