J2 680 System Manual
Version 1.0 May 11, 2012
18
Serial ports
The 680 has four external RS232 serial ports, all of which can be powered. The serial
ports are standard RS-232 ports with a DB9 male connector. The serial ports, in a normal
configuration, are mapped to COM 1-4.
There also four internal serial ports one of which is used for the resistive touch controller
and the other are reserved for other internal options.
COM ports 1-4 can supply power to an external device when required, like the optional
J2 Customer Display. COM 1 can 5 volt and COM 2-4 12 volts. The
voltage is supplied on pin 9 (RI) of the DB9 connector. The maximum current is 1000ma
and is over-current protected. A BIOS setting is used to enable the voltage on each port.
J2 does not normally recommend using the +5 volt option on COM 1 and is only there for
some legacy devices. The problem is it easy for +5 volt device to be plugged into a +12
enable serial port by mistake which will burn out the +5 volt device. A good alternative
to powering a +5 volt serial device, or any +5V device would be to use power from an
unused USB port. Cables for this are readily available (see below).
DB9 pin out serial ports
Serial Port
Pin RS232
1
DCD
2
RD
3
TD
4
DTR
5
GND
6
DSR
7
RTS
8
CTS
9
RI
USB to +5V cable
