Bolymin BETA903A, User Manual, Page: 43 / 95

BETA903A USER MANUAL - 43 -
3.4.
3.4.1.
GPIO test
Recommended interfacing circuit to GPIO
BETA903A supports 4 sets of photo-couple r inputs and 4 sets of photo-couple r outputs for
general purpose inputs/outputs. Those I/Os are useful to read out signals and access control
devices.
Input circuit examples:
Shunt IN1 pin and GND with a switch or sensor, and connect IN1 to external voltage with
current-limiting resistor, Rext. GI_INPUT1 pin on lower left corner will stay high if switch or
sensor is short-circuited. Among which the GI_INPUT1 is a software-defined parameter,
please refter to chapter
4.6 for details. On the other hand, GI_INPUT will at its low level if
switch or sensor is open.
BETA903A
Note: The value of Rext depends on that of Vext. The rule of thumb is keep Iext(min current) at
a typical value of 5mA , and Iext(max) at 14mA. If Rext=0 , set Vext to 12 volt, then Iext
will be 12mA
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