SARA-R4 series - System integration manual
UBX-16029218 - R20 Design-in Page 91 of 128
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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 or SARA-R422M8S modules, and
it is not supported by current product versions of SARA-R410M or 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 or SARA-R422M8S modules, and
it is not supported by current product versions of SARA-R410M or 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 [11], 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.
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