[ale] DTR on serial port

[Chris Fowler]

This is weird.

Yesterday I built a serial port to CW keying interface on proto board.
It has a LED to indicate when it is keyed.  There is a program in Linux
that controls DTR for keying.  DTR on will key the radio.

Radio is off (thankfully) and this morning I plugged my USB printer into
the USB port.  DTR goes active on ttyS1 and LED turns on.  Why?

The printer is USB.  TTYS1 is the 2nd serial port on  a PCI board (Not
USB).  These two things seem unrelated to me.

I've killed and destroyed modem-manager.  It is a real PITA.  

Incidentally, if anyone is interested in one of these interfaces I've
laid it out in Eagle Cad and sent it to batchpcb.  The components are
cheap and I believe the boards are $5.52/ea.  Small and will fit in
Altoids tin.


Chris