User's Manual

HE910 Hardware User Guide
1vv0300925 Rev.9 – 07-02-2012
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 60 of 80
12.2 Using a GPIO Pad as INPUT
The GPIO pads, 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 1.8V CMOS levels of the GPIO.
If the digital output of the device to be connected with the GPIO input pad has interface
levels different from the 1.8V CMOS, then it can be buffered with an open collector
transistor with a 47K pull up to 1.8V.
NOTE:
In order to avoid a back powering effect it is recommended to avoid having any HIGH
logic level signal applied to the digital pins of the HE910 when the module is powered
off or during an ON/OFF transition.
12.3 Using a GPIO Pad as OUTPUT
The GPIO pads, when used as outputs, can drive 1.8V CMOS digital devices or
compatible hardware. When set as outputs, the pads have a push-pull output and
therefore the pull-up resistor may be omitted.