Ublox SARA-R4 Series, Руководство по системной интеграции

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SARA-R4 series - System integration manual
UBX-16029218 - R20 Design-in Page 95 of 128
C1-Public
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ESD sensitivity rating of the GPIO pins is 1 kV (HBM according to JESD22-A114). Higher
protection level could be required if the lines are externally accessible and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor) close to accessible points.
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If the GPIO pins are not used, they can be left unconnected on the application board.
2.8.2 Guidelines for general purpose input/output layout design
The general purpose inputs / outputs pins are generally not critical for layout.
2.9 GNSS peripheral input output
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The GNSS peripheral input output pins are supported by SARA-R422M8SS modules only.
2.9.1 Guidelines for GNSS peripheral input output circuit design
SARA-R422M8S modules provides the following 1.8 V peripheral input output pins directly connected
to the internal u-blox M8 GNSS chipset, as illustrated in
Figure 3 :
• The TXD_GNSS pin consisting in the UART data output of the internal u-blox M8 GNSS chipset:
the line can be connected to a UART data input pin of the application processor (see Figure 66 ).
•
The EXTINT external interrupt pin that can be used for control of the GNSS receiver or for aiding:
the line can be connected to a digital output pin of the application processor (see Figure 66 ).
• The TIMEPULSE output pin that can generate synchronized pulse trains with configurable
intervals / frequency: the line can be connected to a digital input pin of the application processor
(see
Figure 68 ), or it can be connected to a circuit driving an LED (see Figure 66 ).
• The ANT_ON output pin that can provide optional control for switching off power to an external
active GNSS antenna or an external separate LNA (see Figure 42 and Figure 41 ).
SARA-R422M8S
3V8
Time Pulse
45 TIMEPULSE
46
EXTINT
47
TXD_GNSS
Output
RXD
GND GND
Application
Processor
VCC
1V8
Test-Point
Figure 66: Application circuit for GNSS peripheral input output
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It is recommended to provide accessible test point directly connected to the TXD_GNSS pin for
diagnostic purpose.
2.9.2 Guidelines for GNSS peripheral input output layout design
The GNSS peripheral input output pins are generally not critical for layout.