From: Kenn Humborg (kenn at domain bluetree.ie)
Date: Wed 04 Aug 1999 - 12:38:39 IST
"John P. Looney" wrote:
> I was wondering. Would it be possible to write a device driver that would
> use the standard serial code in an odd way...by providing a device that is
> like a serial port, but it's reversed,like the way a null-modem cable is,
> but in software ? As I understand it, a null-modem cable just crosses over
> the send and revice lines. Could you get a serial port to output on it's
> input lines ?
No. An RS232 I/O chip has level converters to convert 5V logic
to and from +/-12V RS232 levels. The input pins (RX, etc) do
12V->5V and the outputs do 5V->12V. The circuits are quite
different in each case.
It would be technically possibly to design a circuit that could
go either way, but since zero people want to do that, and the
RS232 spec doesn't say it's necessary, nobody's going to make
chips that way. It'd be a waste of engineering time/money.
You'll have to dig out a soldering iron or an RS232 breakout
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