WinDbg kernel debugging using serial connection problem

WINDBG
1

I have used WinDbg for kernel debugging with serial connection with no issues in the past. However, we have a system with an Adlink controller running Win10. For some reason I am not able to do kernel debugging using the serial port, nothing is coming out of the port when Windows boots up. Once Windows is up I am able to use the port (for our application) with no problems. Any ideas?

2

Rony wrote:

I have used WinDbg for kernel debugging with serial connection with no issues in the past. However, we have a system with an Adlink controller running Win10. For some reason I am not able to do kernel debugging using the serial port, nothing is coming out of the port when Windows boots up. Once Windows is up I am able to use the port (for our application) with no problems. Any ideas?

Do you have a product number on the Adlink controller?  The kernel
debugger doesn’t use any drivers.  It pounds the serial port registers
directly.  That means the serial port must exactly support the I/O port
ranges and interrupt vectors that the 8250 UART uses. For COM1, it must
respond to I/O ports 3F8-3FF and IRQ 4.  COM2 must respond to I/O ports
2F8-2FF and IRQ 3.  If the Adlink is a PCI device with programmable port
ranges, it cannot be used for kernel debugging.

3

Thanks Tim. The Adlink controller is an Express-HLE.

4

Rony wrote:

Thanks Tim. The Adlink controller is an Express-HLE.

That board uses an Intel QM87 chipset, and it apparently has an LPC that exposes the standard COM1 and COM2 port numbers. Have you triple checked the serial port setting in “bcdedit” to make sure the baud rate matches? And you’re using a regular null modem cable?

But since you’re running Win 10, you’ll probably be happier with Ethernet debugging. It’s a much better experience.

5

Yes I did the basic checks to make sure everything is OK but with no luck. FYI, during development we used the controller on top of a development baseboard we purchased from Adlink which provided easy to use serial connectors. The baseboard includes a super IO chip (Winbond W83627DHG) connected to the LPC bus. With that setup the serial debugging worked.

Thanks Tim. I’ll switch to Ethernet but was curious about this issue.