I already know that pin 5 of a DB-9 connector (RS-232) is SG (signal
ground).
what I haven’t been able to figure out is from what pin does a
mouse get it’s power from? Can anyone out their help?
31
Jan
Power pin for Rs-232/DB-9 connector
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nemisys wrote:
> I already know that pin 5 of a DB-9 connector (RS-232) is SG (signal
> ground).
> what I haven’t been able to figure out is from what pin does a
> mouse get it’s power from? Can anyone out their help?
External equipment that runs on very low power, can steal a
little bit of power from some of the serial port control
signals. For instance, DTR (data terminal ready) and RST
(request to send) will have about +12 volts when set high
by the software. Don’t expect to draw too much current from
these lines.
Ray
nemisys (nemi…@uniserve.com) wrote:
: I already know that pin 5 of a DB-9 connector (RS-232) is SG (signal
: ground).
: what I haven’t been able to figure out is from what pin does a
: mouse get it’s power from? Can anyone out their help?
The mouse gets its + power from the DTR pin and the negative power is
sucked from the TD pin which is negative most of the time. RTS and other
PC output pins are sometimes diode ORed to get more current.
You can read more about it in the serial FAQ or the ibm-pc hardware FAQ.
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