Subject: Re: RS232 Serial connection problem
To: None <u0giene@yahoo.com>
From: Dieter <netbsd@sopwith.solgatos.com>
List: netbsd-help
Date: 06/12/2005 23:23:45
> I'm left over with 2 pins on cisco that are DSR(Data Set Ready)
> and DTR(Data Terminal Ready) which according to some people I
> spoke with arent that important.

Whichever one is an input to the Cisco (which depends on which
gender the port is (term or comm) probably needs to be tied high.

Same with RTS/CTS.

Make sure both sides are using the same baud rate, same parity, etc.

The small inline boxes with the 7 LEDs are very useful for
getting this job sorted out.  Start by attaching it
to one side at a time, and observe which pins each device is
driving.  If both are driving Receive Data or if both are
driving Transmit Data, you'll need to do the null modem (crossover)
wiring.  A breakout box, either combined with the LEDs or
separate is useful for experimenting.  Once you get the wiring sorted
out you fire up the soldering iron and build a permanent adapter.

To start with, I'd suggest getting Receive Data, Transmit Data,
and ground connected correctly.  Make sure all other inputs
see a high signal.  You should then be able to get some data moving.
Step two would be to try and get hardware flow control working,
assuming both sides support it.  This should be RTS/CTS, but
might be DTR/DSR, or pretty much any combination depending
of what the designer was smoking that day.  "The nice thing about
standards is there are so many to choose from."

> http://www.netbsd.org/Documentation/Hardware/Misc/serial.html#mac

Interesting.  Mac is supposed to be differential/balanced, but
doesn't have enough pins?  Yeah that sounds like Apple.