Re: [pyusb-users] Specifying bRequest, wValue, wLength and wIndex in non-control requests

[Xiaofan C. <xia...@gm...>]

On Mon, Oct 14, 2019 at 4:52 PM Joel Snape <jo...@sn...> wrote:
>
> Hi,
>
> I'm trying to reverse engineering something with a windows driver, but I'm
> having trouble replicating one of the reads it makes with pyUSB.
>
> The driver sends a read-request on each endpoint, with different wValue,
> wIndex and wLength fields set. I can see how to do this on the control
> channel with pyUSB (using dev.ctrl_transfer), but I can't see how to set these if I'm
> doing a read request as that just takes a length...
>
> The driver packet looks like this in wireshark:
>
> ...
> Endpoint: 0x80, Direction: IN
> <snip>
> URB:
> bmRequestType: 0xc0
> bRequest: 4
> wValue: 0x0040
> wIndex: 0 (0x0000)
> wLength: 8
>
> I'm not sure if I'm missing something about how USB works, or
> how pyUSB works....any pointers much appreciated!

The above is a Control IN transfer. 0x80 (IN) and 0x0 (OUT) refers to
Endpoint 0,
the control endpoint.

You may want to read USB Made Simple here.
http://www.usbmadesimple.co.uk/

-- 
Xiaofan