SARA-R4 series - System Integration Manual
UBX-16029218 - R06
Design-in
Page 71 of 102
2.6.3
SPI interface
2.6.3.1
Guidelines for SPI circuit design
The SPI interface is not supported by “00”, “01” and “02” product versions: the SPI interface pins should
not be driven by any external device.
2.6.4
SDIO interface
2.6.4.1
Guidelines for SDIO circuit design
The SDIO interface is not supported by “00”, “01” and “02” product versions: the SDIO interface pins
should not be driven by any external device.
2.6.5
DDC (I
2
C) interface
2.6.5.1
Guidelines for DDC (I
2
C) circuit design
DDC (I
2
C) interface is not supported by “00” and “01” product versions: the DDC (I
2
C) interface pins
should not be driven by any external device.
The DDC I
2
C-bus master interface can be used to communicate with u-blox GNSS receivers and other external
I
2
C-bus slaves as an audio codec.
The
SDA
and
SCL
pins of the module are open drain output as per
I
2
C bus specifications
[9], and they have
internal pull-up resistors to the
V_INT
1.8 V supply rail of the module, so there is no need of additional
components on the external application board.
Capacitance and series resistance must be limited on the bus to match the I
2
C specifications (1.0 µs is the
maximum allowed rise time on the
SCL
and
SDA
lines): route connections as short as possible.
ESD sensitivity rating of the DDC (I
2
C) pins is 1 kV (Human Body Model 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 array) close to accessible points.
If the pins are not used as DDC bus interface, they can be left unconnected.
Reference
Description
Part Number - Manufacturer
R1
47 k
Ω
Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
U1
Voltage Regulator for GNSS receiver
See GNSS receiver Hardware Integration Manual
2.7
Audio
2.7.1.1
Guidelines for Audio circuit design
Audio is not supported by “00”, “01” and “02” product versions: the I
2
S interface pins should not be
driven by any external device.