11. Serial Device Communications (Si5372 ↔ MCU)
11.1 Onboard SPI Support
The MCU on-board the Si5372-EVB communicates with the Si5372 device through a 4-wire SPI (Serial Peripheral Interface) link. The
MCU is the SPI master and the Si5372 device is the SPI slave. The Si5372 device can also support a 2-wire I
2
C serial interface, al-
though the Si5372-EVB does NOT support the I
2
C mode of operation. SPI mode was chosen for the EVB because of the relatively
higher speed transfers supported by SPI vs. I
2
C.
11.2 External I
2
C Support
I
2
C can be supported if driven from an external I
2
C controller. The serial interface signals between the MCU and Si5372 pass through
shunts loaded on header J17. These jumper shunts must be installed in J17 for normal EVB operation using SPI with CBPro. If testing
of I
2
C operation via external controller is desired, the shunts in J17 can be removed thereby isolating the on-board MCU from the
Si5372 device. The shunt at JP1 (I2C_SEL) must also be removed to select I
2
C as Si5372 interface type. An external I
2
C controller
connected to the Si5372 side of J17 can then communicate to the Si5372 device. (For more information on I
2
C signal protocol, please
refer to the Si5372 data sheet.)
The figure below illustrates the J17 header schematic. J17 even numbered pins (2, 4, 6, etc.) connect to the Si5372 device and the odd
numbered pins (1, 3, 5, etc.) connect to the MCU. Once the jumper shunts have been removed from J17 and JP1, I
2
C operation should
use J17 pin 4 (DUT_SDA_SDIO) as the I
2
C SDA and J17 pin 8 (DUT_SCLK) as the I
2
C SCLK. Please note the external I
2
C controller
will need to supply its own I
2
C signal pull-up resistors.
Figure 11.1. Serial Communications Header J17
UG372: Si5372 Evaluation Board User’s Guide
Serial Device Communications (Si5372 ↔ MCU)
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