User's Manual
HC864-AUTO Hardware User Guide
1vv0300946 Rev.4 – 2012-12-27
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 54 of 77
11.2. 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/2.6V
CMOS levels of the GPIO.
If the digital output of the device is connected with the GPIO input, the pad has interface
levels different from the 1.8V/2.6V CMOS. It can be buffered with an open collector
transistor with a 47K pull-up resistor to 1.8V/2.6V.
11.3. Using a GPIO Pad as Output
The GPIO pads, when used as outputs, can drive 1.8V/2.6V 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.