PORTS Forum

Ports and Interfaces => USB => Topic started by: DosMan on January 01, 2016, 08:47:10 pm

Title: Discrepancy in MS extended compat ID in USB Complete 5th edition
Post by: DosMan on January 01, 2016, 08:47:10 pm

In USB Complete 5th Edition, chapter 15 discusses the Microsoft extended compat ID OS feature descriptor. In table 15-2, it says the dwLength field requires 4 bytes. But in listing 15-1, the initializer for the descriptor appears to allow only 2 bytes for length ("0x28, 0x00"). Which is correct? Or am I reading this wrong?

Title: Re: Discrepancy in MS extended compat ID in USB Complete 5th edition
Post by: Jan Axelson on January 01, 2016, 09:08:41 pm

dwLength is 4 bytes. Thank you for pointing that out.

Title: Re: Discrepancy in MS extended compat ID in USB Complete 5th edition
Post by: DosMan on January 02, 2016, 08:16:36 pm

There seems to be an issue with the next field as well. The table says to use 0x0100 for bcdVersion, but the listing has "0x01, 0x00" which would be 0x0001. In part 2 of the listing, in the initialization of the extended properties descriptor, it's shown correctly as "0x00, 0x01".

I've just been working on this stuff, getting my USB device to spit out these descriptors.

Title: Re: Discrepancy in MS extended compat ID in USB Complete 5th edition
Post by: Jan Axelson on January 02, 2016, 08:58:52 pm

Thank you again.