Re: other_speed_configuration string

[Tim R. <ti...@pr...>]

Walker, Richard wrote:
>> Are you fetching descriptor type 7, or are you fetching string (type 3)
>> descriptor number 7?  Those are two different things.  Rather than
>> subvert the meaning of the actual OTHER_SPEED_CONFIGURATION descriptor...
> I'm not sure.  I know that the value we need is an ascii-encoded string, so I suspect it will be a string type.  I've included the technical description from the data sheet, so that maybe the implementation will be obvious to someone more familiar with the USB protocol.
>
> Currently the debug info that I need to access is described in the data sheet as:
>
> 2.3.5.17: String Descriptor for Other Speed Configuration String
>
>    offset    field                  value in byte order
>    --------  -------                ------------------------------
>       0      bDescLength            0x4e
>       1      bDesciptorType         0x03
>             2            wLangID                               debug information encoded ascii string

bDescriptorType = 3 means it is a string descriptor.  You just need to
know which string descriptor it is.  There are a number of string
descriptors (usually 1=manufacturer, 2=product, 3=serial number); you
just need to know which one it is.  The documentation probably tells you
that; there should be an "Other Speed Configuration Descriptor" listed
that has an iConfiguration value.  That's the number you need.

So, libusb_get_string_descriptor( dev, (the iConfiguration  number),
0x0409,  buffer, length ).

-- 
Tim Roberts, ti...@pr...
Providenza & Boekelheide, Inc.