Telit Wireless Solutions GE863-QUAD - Manual (Page 55)

GE863-QUAD
GE863-PY
1vv0300715 Rev. 1 - 19/09/06
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 55 of 79
10 General Purpose I/O
The general purpose I/O pads can be configured to act in three different ways:
- input
- output
- alternate function (internally controlled)
Input pads can only be read and report the digital value (high or low) present on the pad at the read
time; output pads can only be written or queried and set the value of the pad output; an alternate
function pad is internally controlled by the GE863-QUAD / PY firmware and acts depending on the
function implemented.
Not all GPIO pads support all these three modes:
- GPIO5 supports all three modes and can be input, output, RFTX monitor output (Alternate
function)
- GPIO6 supports all three modes and can be input, output, alarm output (Alternate function)
- GPIO7 supports all three modes and can be input, output, buzzer output (Alternate function)
All GPIO pads are 2.8V CMOS signals and their interface levels are the same specified in the
paragraph 5 .
10.1 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 2.8V 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 2.8V CMOS, then it can be connected to GPIO1 or can be buffered with an open collector
transistor, provided a 47KΩ pull-up resistor is connected as seen in the paragraph 6.4 5V UART level
translation.
10.2 Using a GPIO Pad as OUTPUT
The GPIO pads, when used as outputs, can drive 2.8V 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.