About String and Report Descriptors.

NTDEV
1

Hi there!
I?m experiencing some headaches concerning String Descriptor and Report Descriptor in HID Stack. Here they go:

  1. Is there a numeric limit in manufacturer, product and serial number fields in String Descriptor?
  2. I tried to understand how to build a Report Descriptor, but reading in Oney?s book, he says about HID Descriptor Tool, that was discontinued and substitued by USBCV, but I couldn?t understand how USBCV can help. Any experienced user can give me a help?

Thank you so much!

Lucas.

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2

Considering they are one byte each, one would have to say the possible numeric range is 0 to 255.

d

From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of Lucas Bracher
Sent: Thursday, December 14, 2006 12:43 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] About String and Report Descriptors.

Hi there!
I?m experiencing some headaches concerning String Descriptor and Report Descriptor in HID Stack. Here they go:

  1. Is there a numeric limit in manufacturer, product and serial number fields in String Descriptor?
  2. I tried to understand how to build a Report Descriptor, but reading in Oney?s book, he says about HID Descriptor Tool, that was discontinued and substitued by USBCV, but I couldn?t understand how USBCV can help. Any experienced user can give me a help?

Thank you so much!

Lucas.??

Novidade no Yahoo! Mail: receba alertas de novas mensagens no seu celular. Registre seu aparelho agora!

Questions? First check the Kernel Driver FAQ at http://www.osronline.com/article.cfm?id=256

To unsubscribe, visit the List Server section of OSR Online at http://www.osronline.com/page.cfm?name=ListServer

3

Lucas Bracher wrote:

Hi there!
I´m experiencing some headaches concerning String Descriptor and
Report Descriptor in HID Stack. Here they go:

  1. Is there a numeric limit in manufacturer, product and serial number
    fields in String Descriptor?
  2. I tried to understand how to build a Report Descriptor, but reading
    in Oney´s book, he says about HID Descriptor Tool, that was
    discontinued and substitued by USBCV, but I couldn´t understand how
    USBCV can help. Any experienced user can give me a help?

If you have not already downloaded the USB 2.0 and USB HID Class
specifications from www.usb.org, you should do so at once. They are
surprisingly readable, as protocol specs go.

String descriptors are basically limited to 126 characters. The string
descriptor length field is 8 bits; that holds the length of the string
in bytes, including the zero terminator, and the strings are in Unicode
UCS16, so there are 2 bytes per character.

The USB HID specs have sample report descriptors that may help you.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.

4

AFAIK, the string descriptor is not required to be NULL terminated since it contains its own length in the descriptor itself, or did I miss that part of the spec that requires NULL termination?

-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of Tim Roberts
Sent: Thursday, December 14, 2006 2:11 PM
To: Windows System Software Devs Interest List
Subject: Re: [ntdev] About String and Report Descriptors.

Lucas Bracher wrote:

Hi there!
I?m experiencing some headaches concerning String Descriptor and
Report Descriptor in HID Stack. Here they go:

  1. Is there a numeric limit in manufacturer, product and serial number
    fields in String Descriptor?
  2. I tried to understand how to build a Report Descriptor, but reading
    in Oney?s book, he says about HID Descriptor Tool, that was
    discontinued and substitued by USBCV, but I couldn?t understand how
    USBCV can help. Any experienced user can give me a help?

If you have not already downloaded the USB 2.0 and USB HID Class
specifications from www.usb.org, you should do so at once. They are
surprisingly readable, as protocol specs go.

String descriptors are basically limited to 126 characters. The string
descriptor length field is 8 bits; that holds the length of the string
in bytes, including the zero terminator, and the strings are in Unicode
UCS16, so there are 2 bytes per character.

The USB HID specs have sample report descriptors that may help you.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.

Questions? First check the Kernel Driver FAQ at http://www.osronline.com/article.cfm?id=256

To unsubscribe, visit the List Server section of OSR Online at http://www.osronline.com/page.cfm?name=ListServer

5

Doron Holan wrote:

AFAIK, the string descriptor is not required to be NULL terminated since it contains its own length in the descriptor itself, or did I miss that part of the spec that requires NULL termination?

You are correct. The length is limited to 126 characters, but that’s
because the string descriptor length includes the length byte and the
descriptor type byte, not a zero-terminator.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.