Kernel debug with USB to serial converter

Got a laptop without a serial port, and since I’ve had no luck with modem
debugging (my host is Win2K and the modem has never worked well - rarely
connecting to anything and slow those few times it does connect), I got a
USB to serial converter. It works like a champ for everything else I’ve
tested it on, including using HyperTerminal to check the null modem cable.
I’ve used the host to kernel debug other machines and have the boot.ini
opts set on the target for the com port the USB converter creates/uses.
But no luck. Anyone have any ideas?

Thanks.

Scott

Puzzling this is, isn’t it ?

Ok, I give you some hints why it is not working.

  1. What is the difference between a COM-Port mapped via an
    USB and a COM-Port accessed via CPU IO-bus ?
  2. When using a Kernel-Debugger to stop the target system what parts
    of system software (OS) keep running ?

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| Stollmann E+V GmbH, Development | http://www.stollmann.de |
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Got a laptop without a serial port, and since I’ve had no luck with modem
debugging (my host is Win2K and the modem has never worked well - rarely
connecting to anything and slow those few times it does connect), I got a
USB to serial converter. It works like a champ for everything else I’ve
tested it on, including using HyperTerminal to check the null modem cable.
I’ve used the host to kernel debug other machines and have the boot.ini
opts set on the target for the com port the USB converter creates/uses.
But no luck. Anyone have any ideas?

Thanks.

Scott


You are currently subscribed to windbg as: xxxxx@stollmann.de
To unsubscribe send a blank email to %%email.unsub%%

When you set a target to use a com port for debugging, the debugging engine
takes over the port and drives it itself. This is why a com port will no
longer appear in device manager when being used for debugging. Now, say you
try to use a port on a USB device. When the system first boots, that port do
not exist according to the system hardware. Therefore there is no such thing
as COMX, so it just doesn’t work. Ports on USB-Serial converters do not get
created until later on when the PNP manager loads the driver for the USB
device.

Hope this helps, Chris

----- Original Message -----
From:
To: “Kernel Debugging Interest List”
Sent: Thursday, June 20, 2002 12:33 AM
Subject: [windbg] Kernel debug with USB to serial converter

> Got a laptop without a serial port, and since I’ve had no luck with modem
> debugging (my host is Win2K and the modem has never worked well - rarely
> connecting to anything and slow those few times it does connect), I got a
> USB to serial converter. It works like a champ for everything else I’ve
> tested it on, including using HyperTerminal to check the null modem cable.
> I’ve used the host to kernel debug other machines and have the boot.ini
> opts set on the target for the com port the USB converter creates/uses.
> But no luck. Anyone have any ideas?
>
> Thanks.
>
> Scott
>
> —
> You are currently subscribed to windbg as: xxxxx@connecttech.com
> To unsubscribe send a blank email to %%email.unsub%%

Plus when the machine halts the UDB driver stack doesn’t function.
Gettting the driver stack for a device to work when the OS is crashed is
a non-trival task.

If the laptop is running XP then you can do 1394 debugging via a 1394 PC
card or built in port.

-----Original Message-----
From: Chris Dore [mailto:xxxxx@connecttech.com]
Sent: Thursday, June 20, 2002 6:30 AM
To: Kernel Debugging Interest List
Subject: [windbg] Re: Kernel debug with USB to serial converter

When you set a target to use a com port for debugging, the debugging
engine takes over the port and drives it itself. This is why a com port
will no longer appear in device manager when being used for debugging.
Now, say you try to use a port on a USB device. When the system first
boots, that port do not exist according to the system hardware.
Therefore there is no such thing as COMX, so it just doesn’t work. Ports
on USB-Serial converters do not get created until later on when the PNP
manager loads the driver for the USB device.

Hope this helps, Chris

----- Original Message -----
From:
To: “Kernel Debugging Interest List”
Sent: Thursday, June 20, 2002 12:33 AM
Subject: [windbg] Kernel debug with USB to serial converter

> Got a laptop without a serial port, and since I’ve had no luck with
> modem debugging (my host is Win2K and the modem has never worked well
> - rarely connecting to anything and slow those few times it does
> connect), I got a USB to serial converter. It works like a champ for
> everything else I’ve tested it on, including using HyperTerminal to
> check the null modem cable. I’ve used the host to kernel debug other
> machines and have the boot.ini opts set on the target for the com port

> the USB converter creates/uses. But no luck. Anyone have any ideas?
>
> Thanks.
>
> Scott
>
> —
> You are currently subscribed to windbg as: xxxxx@connecttech.com To
> unsubscribe send a blank email to %%email.unsub%%


You are currently subscribed to windbg as: xxxxx@microsoft.com To
unsubscribe send a blank email to %%email.unsub%%

At 06.33 20/06/2002, you wrote:

Got a laptop without a serial port, and since I’ve had no luck with modem
debugging (my host is Win2K and the modem has never worked well - rarely
connecting to anything and slow those few times it does connect), I got a
USB to serial converter. It works like a champ for everything else I’ve
tested it on, including using HyperTerminal to check the null modem cable.
I’ve used the host to kernel debug other machines and have the boot.ini
opts set on the target for the com port the USB converter creates/uses.
But no luck. Anyone have any ideas?

Only ports with built-in logic can be used as debug ports. Think about it:
if the kernel is stopped by the debugger, what driver will drive the port?
None. Only ports that are able to “drive themselves”, with little or no
effort from the software (e.g. COM ports can be written to with CPU
instructions), are usable for kernel debugging. USB is a “dumb” interface,
it can only be used to send commands to the attached devices, *not* raw
data like serial and FireWire