User Manual
LARA-R2 series - System Integration Manual
UBX-16010573 - R02 Objective Specification Design-in
Page 110 of 148
Connection with u-blox 1.8 V GNSS receivers
Figure 60 shows an application circuit for connecting the cellular module to a u-blox 1.8 V GNSS receiver:
The SDA and SCL pins of the cellular module are directly connected to the related pins of the u-blox 1.8 V
GNSS receiver, with appropriate pull-up resistors connected to the 1.8 V GNSS supply enabled after the
V_INT supply of the I
2
C pins of the cellular module.
The GPIO2 pin is connected to the active-high enable pin of the voltage regulator that supplies the u-blox
1.8 V GNSS receiver providing the “GNSS supply enable” function. A pull-down resistor is provided to avoid
a switch on of the positioning receiver when the cellular module is switched off or in the reset state.
The GPIO3 and GPIO4 pins are directly connected respectively to TXD1 and EXTINT0 pins of the u-blox
1.8 V GNSS receiver providing “GNSS Tx data ready” and “GNSS RTC sharing” functions.
The V_BCKP supply output of the cellular module is connected to the V_BCKP backup supply input pin of
the GNSS receiver to provide the supply for the GNSS real time clock and backup RAM when the VCC supply
of the cellular module is within its operating range and the VCC supply of the GNSS receiver is disabled. This
enables the u-blox GNSS receiver to recover from a power breakdown with either a hot start or a warm start
(depending on the actual duration of the GNSS VCC outage) and to maintain the configuration settings
saved in the backup RAM.
R1
INOUT
GND
GNSS LDO
Regulator
SHDN
u-blox GNSS
1.8 V receiver
SDA2
SCL2
R2
1V8 1V8
VMAIN1V8
U1
23
GPIO2
SDA
SCL
C1
TxD1
EXTINT0
GPIO3
GPIO4
26
27
24
25
VCC
R3
V_BCKP V_BCKP
2
GNSS data ready
GNSS RTC sharing
GNSS supply enabled
LARA-R2 series
(except ‘02’ product version)
Figure 60: Application circuit for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers
Reference
Description
Part Number - Manufacturer
R1, R2
4.7 kΩ Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
47 kΩ Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
U1
Voltage Regulator for GNSS receiver
See GNSS receiver Hardware Integration Manual
Table 44: Components for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers