Re: [Libusb-devel] USB VID/PID for open source projects

[Segher B. <se...@ke...>]

>> Yes different boards should be identifiable somehow, and I think
>> vidpid has advantages over any other field, in or out of the device
>> descriptor. vidpid is usually always visible for user in some way,
>> while other fields may not be.
>
> It may well partly due to the difficulty to get a valid PID that companies
> are using the same PID for different product and then differentiate
> the product using strings in the descriptor or other methods.
>
> The other reason may be WHQL. One example is the Amontec Jtagkey.
> http://www.amontec.com/download/amontec-jtagkey-driver-d2xx-20091124.zip
> This driver works with all Amontec JTAGkey dongles (Amontec JTAGkey /
> JTAGkey Tiny / JTAGkey-2 / JTAGkey-2P / JTAGkey-2 Tiny, etc).

There are also many clones of the jtagkey that use the same vid/pid.

This device is also a good example of why it is *bad* to use the same
vid/pid on multiple devices: all of them seem to be different in the
sense of the TRST and SRST outputs (polarity, push/pull vs. open drain).
This makes it impossible to use a jtagkey (clone; it might just be the
clones that differ!) without looking at the device strings first, to
properly identify the device.


Segher