Rainbow Electronics GM862-GPS - Manual (Page 64)

GM862-GPS Hardware User Guide
1vv0300728 Rev. 8 - 20/09/07
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 64 of 73
10.2 Using a GPIO pin as INPUT
The GPIO pins, when used as inputs, can be connected to a digital output of another device and
report its status, provided this device has interface levels compatible with the 2.8V CMOS levels of the
GPIO.
If the digital output of the device to be connected with the GPIO input pin has interface levels different
from the 2.8V CMOS, then it can be connected to GPIO1 or can be buffered with an open collector
transistor, provided with a 47KΩ pull-up resistor to 2.8V.
10.3 Using a GPIO pin as OUTPUT
The GPIO pins, when used as outputs, can drive 2.8V CMOS digital devices or compatible hardware.
When set as outputs, the pins (except from GPIO2 which is Open Collector) have a push-pull output
and therefore the pull-up resistor may be omitted.
The GPIO2 pin, since it is an Open Collector output needs an external pull-up resistor.
10.4 Using the RF Transmission Control GPIO4
The GPIO4 pin, when configured as RF Transmission Control Input, permits to disable the Transmitter
when the GPIO is set to Low by the application.
10.5 Using the RFTXMON Output GPIO5
The GPIO5 pin, when configured as RFTXMON Output, is controlled by the GM862-GPS module and
will rise when the transmitter is active and fall after the transmitter activity is completed.
For example, if a call is started, the line will be HIGH during all the conversation and it will be again
LOW after hanged up.
The line rises up 300ms before first TX burst and will became again LOW from 500ms to 1sec after
last TX burst.