Subject: Re: Serial console: won't boot unless the cable is plugged in
To: Mark Cullen <mark.r.cullen@gmail.com>
From: Steven M. Bellovin <smb@cs.columbia.edu>
List: netbsd-users
Date: 07/03/2006 20:18:09
On Mon, 03 Jul 2006 23:59:07 +0100, Mark Cullen <mark.r.cullen@gmail.com>
wrote:

> 
> Not really an option I am afraid. Said laptop is getting donated to my 
> parents and won't be in my room for much longer, which is why I would 
> really like it to boot properly without the cable plugged in.
> 
Here's a hardware hack: get a connector, and hardware DTR to CD.  When the
device is opened, DTR *should* be asserted; by wiring it to CD, the port
will appear ready.  Alternatively, it may be waiting to see CTS; again,
wire DTR to it.  Hmm -- some devices look for DSR instead of CD...  Best
is to loop RTS to CTS, and DTR to CD and DSR.  

You may want to get hold of a breakout box and try it first.  Any decent
breakout box will let you open any line, connect it to any other, etc.
Have a look at http://www.lammertbies.nl/comm/cable/RS-232.html -- though
I can't vouch for the site, I used to play with RS-232 cables a lot, and
the data looks accurate.

		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb