How to Debug the Windows OS using USB

Who may be interested in this article?

First of all, information in this article will be interesting for the developers of drivers and Windows OS low level components that can function in the kernel mode. Also, this article can be interesting for engineers and analysts that develop devices, which interact with Windows OS.

Evolution of Debug Modes

In this part of the article, I will give a short description of how the tools and methods of the Windows debug modes evolved together with the development of software and hardware.

Host + COM + Target

Formerly, the host machine + target machine pair was used for debugging of drivers or Windows OS components. Both computers were connected with the null modem cable via the serial port. Then, on one of the machines (host machine), the debugger application started and, on another machine (target machine), the driver or OS component to be debugged started. The main shortcoming was the low speed of data transfer that, in its turn, influenced the debugging speed significantly.

Host + FireWire + Target

After the appearance of the firewire interface, the data transfer speed increased notably. This made the debugging process more pleasant and, at the same time, caused one serious problem. The support of this mode appeared starting from the Windows XP OS.

The motherboard of one of the machines may not have the built-in fireware interface. This problem can be easily solved for the PC by installing the additional PCI expansion card, which carries one or many additional interfaces (COM, firewire, USB). Concerning the portable devices, such as laptops, installation of the expansion card does not always help to perform the debug mode via the additional interfaces.

One should also remember that the installation of expansion cards is not always possible.

Host + USB + Target

Today, the USB interface is the most popular among the data transfer interfaces as it combines the high speed and simplicity of usage. There was no support for debugging via USB interface in Windows OS 2000 - 2003. Such support appeared starting from Windows Vista OS.

There is a sequence of rules and tips that should be performed before the debugging mechanism via USB bus is operable. The most important is that the USB interface is present practically on all devices where Windows Vista OS or later versions of this family can be installed. This, in its turn, increases the chance that when the hard-to-detect bug appears, we will be able to use modern debugging facilities for its removal.

Next, I will describe a number of rules and tips that will help you to perform the debugging via the USB bus.

Preparation Steps for Windows OS Debugging Using USB Bus

In this part of the article, there are 7 steps and several tips of how to perform the Windows OS debugging using the USB bus.

Step 1: Buy or borrow a special device for USB debugging

You need to use a special USB 2.0 debug cable device to perform the Host Machine + USB + Target Machine debugging mechanism. This cable is not a standard USB 2.0 cable, because it has an extra hardware component that makes it compatible with the USB2 Debug Device Functional Specification. You can find these cables with an Internet search for "USB 2.0 debug cable".

In the current experiment, I used the NET20DC device produced by Ajays company that is displayed on Figure 1.

Read more: Codeproject

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