Appendix E
AirAura GPIO Interface
AirAura is equipped two GPIO (General Purpose Input/Output) control interfaces;
an eight input optoisolated interface for selecting presets in the first eight memory
slots and a four output optoisolated interface that can be used to remotely signal
status about the processor.
GPI – General Purpose Input
The GPI interface provides eight separate General Purpose Inputs which share a
common DC return. The interface connector is a female DB-9 connector with the
following pin assignments. Note that all pins are isolated from AirAura internal
circuitry!
GPI Input Number
DB-9 Connector Pin Number
One Pin
6
Two Pin
2
Three Pin
7
Four Pin
3
Five Pin
8
Six Pin
4
Seven Pin
9
Eight Pin
5
Common Return
Pin 1
The GPI input circuits are optoisolated by devices having exceptional
input/output isolation. These inputs are designed to work very well in high RF
environments and should not cause ground loop issues when connected to
external equipment.
Each of the GPI inputs is current limited by a 475 ohm internal resistance. The
LED device inside the optoisolators is rated at a maximum forward current of
50mA and a normal operating current of 5mA.
Before connecting external circuitry to the GPI inputs,
first ascertain whether it will be necessary to utilize
additional outboard series resistance in your application!
