Integration Manual

Table Of Contents
SARA-R4 series - System integration manual
UBX-16029218 - R20 Design-in Page 92 of 129
C1-Public
2.6.3 SPI interface
2.6.3.1 Guidelines for SPI circuit design
The SPI interface is not available on SARA-R422, SARA-R422S and SARA-R422M8S modules, and
it is not supported by current product versions of SARA-R410M and SARA-R412M modules: 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 available on SARA-R422, SARA-R422S and SARA-R422M8S modules,
and it is not supported by current product versions of SARA-R410M and SARA-R412M modules:
the SDIO interface pins should not be driven by any external device.
2.6.5 DDC (I2C) interface
2.6.5.1 Guidelines for DDC (I2C) circuit design
DDC (I2C) interface is not supported by the SARA-R410M-01B product version: the DDC (I2C)
interface pins should not be driven by any external device.
The DDC I2C-bus host interface can be used to communicate with u-blox GNSS receivers and other
external I2C-bus devices as an audio codec.
The SDA and SCL pins of the module are open drain output as per I2C bus specifications [10], 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 pull-up resistors on the external application board.
Capacitance and series resistance must be limited on the bus to match the I2C specifications
(maximum proper rise time for SCL / SDA lines is 1.0 µs): route connections as short as possible.
ESD sensitivity rating of the DDC (I2C) 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.
If the pins are not used as DDC bus interface, they can be left unconnected.