VISTEK V1679 single-mode fibre
data transceiver
10
Issue 1
3.3
Examples for Driving V1679 GPI Inputs
3.3.1
Push Button or Relay Driven Switch
A Push Button is a simple example of how a GPI Input can be driven. One should be aware that when using
any type of mechanically actuated switch, the input signal could bounce for several milliseconds before it
reaches a stable state. This implies that the received bit at the far end of the fibre link is unstable for the
same period of time.
The built in Schmitt-Trigger Buffer in the Opto-Isolator can only 'tidy up' slow rising edges, but it cannot
suppress heavily bouncing input signals.
1 0 0 R
3 9 0 R
1 K 8
G P IO n -
G P IO n +
+ 5 V
+ 1 2 V
1 N 4 1 4 8
In p u t B ia s V o lta g e S e le ctio n Ju m p e r
S h o rt to G N D Ju m p e r
(s h o rt)
O n -b o a rd p o w e r s u p p lie s
P u s h B u tto n S w itc h
o r m e ch a n ica lly
a ctu a te d S w itch
(R e la y )
N o te:
T he LE D is p erm a ne ntly 'O N ' as lo ng as the P us h -B utto n is o pe n.
B y c los ing th e s w itch , th e L E D w ill be sh orted an d g oes 'O F F '.
R ea r C o nn ec tor S id e
B o ard S id e
Figure 4 : Example 1