User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 62 of 116
1.10.2 DDC application circuit
The SDA and SCL lines can be used only to connect the LISA module to a u-blox GPS module: LISA DDC (I
2
C)
interface is enabled by the +UGPS AT command (for more details refer to u-blox AT Commands Manual [2]).
GPIO2 is automatically driven as an output by the +UGPS AT command to switch-on or to switch-off the u-blox
GPS module, connecting GPIO2 to the active-high enable pin (or the active-low shutdown pin) of the voltage
regulator that supplies the u-blox GPS module on the application board.
GPIO3 is automatically driven as an input by the +UGPS AT command to sense when the u-blox GPS module is
ready to send data.
GPIO4 is automatically driven as an output by the +UGPS AT command to provide a synchronization timing
signal to the u-blox GPS module.
The application circuit for the connection of a LISA-U1/LISA-H1 series wireless module to a u-blox 1.8 V GPS
receiver is illustrated in Figure 36. A pull-down resistor is mounted on the GPIO2 line to avoid a switch on of the
GPS module when the LISA-U1/LISA-H1 series module is in the internal reset state.
LISA-U1/LISA-H1
series
R1
INOUT
GND
GPS LDO
Regulator
SHDN
u-blox
1.8 V GPS receiver
SDA2
SCL2
R2
1V8 1V8
VMAIN1V8
U1
21
GPIO2
SDA
SCL
C1
TxD1
EXTINT0
GPIO3
GPIO4
46
45
23
24
VCC
R3
Figure 36: DDC Application circuit for u-blox 1.8 V GPS receiver
Reference
Description
Part Number - Manufacturer
R1, R2, R3
4.7 kΩ Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
U1
Voltage Regulator for GPS Receiver
See GPS Receiver Hardware Integration Manual
Table 24: Components for DDC application circuit for u-blox 1.8 V GPS receiver
If a 3 V u-blox GPS receiver is used, the SDA, SCL pins and the GPIO2, GPIO3, GPIO4 pins of the
LISA-U1/LISA-H1 series wireless module cannot be directly connected to the 3 V u-blox GPS receiver, since the
pins of the LISA-U1/LISA-H1 series modules aren’t tolerant up to 3 V. An application circuit for the connection of
a LISA-U1/LISA-H1 series wireless module to a u-blox 3.0 V GPS receiver is illustrated in Figure 37. A pull-down
resistor is mounted on the GPIO2 line to avoid a switch on of the GPS module when the LISA-U1/LISA-H1 series
module is in the internal reset state.