Usb-I C Interface; General Description; Usb Connector; Power Regulator - Analog Devices SSM2380 User Manual

Evaluation Board User Guide
USB—I C INTERFACE
2

GENERAL DESCRIPTION

The EVAL-ADUSB2EBZ, also known as the USBi, is a standa-
lone communications interface adapter and programmer used
in the evaluation of SigmaDSP® systems. It translates USB
control commands from SigmaStudio to the I
communications protocols.
To simplify bench evaluation, an interface based on the USBi
adapter is included on the SSM2380
eliminates the need for a separate interface board and 10-pin
ribbon cable; only a USB mini-B cable is required. This
interface is shown in Figure 16.
2
Figure 16. USB to I C Microcontroller and USB interface
The on-board regulators enable both 1.8 V and 3.3 V IOVDD
operation, allowing for increased testing flexibility.
The USBi interface can also control SigmaDSP systems in
real time via SigmaStudio, and it is capable of programming
an EEPROM in self-boot systems. It is an ideal solution for
in-circuit programming and tuning of prototype systems.
The USBi only supports USB 2.0 interfaces; it does not
work with PCs that only support USB Version 1.0 and
USB Version 1.1.
2 C and SPI
evaluation board. This
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USB CONNECTOR

The connection between the host PC and the Cypress USB
interface device is via a standard USB cable that carries D+ and
D− signals for data communications, a 5 V power supply, and
ground. The D+ and D− lines are a 1-wire communication
interface carried by half-duplex differential signals on a twisted
pair. The clock is embedded in the data using the nonreturn-to-
zero inverted (NRZI) line code. These signal lines connect
directly to pins on the Cypress USB interface.
A surface-mounted USB miniature Type B jack was selected
for its low profile and increasing popularity in consumer
electronics.

POWER REGULATOR

The Cypress USB interface I/O ports are capable of operating
in both 1.8 V and 3.3 V modes, depending on the target device
in the system. Two regulators, one for 5 V to 3.3 V regulation
and the other for 5 V to 1.8 V regulation, run simultaneously
when the board is powered. A jumper (JP4) is provided to
easily switch the IOVDD supply between the two regulators.
D1 provides visual feedback that the board is being supplied
with 5 V power from the PC USB port.
The position of Jumper JP4 should not be changed when the
board is connected to the USB bus.

CYPRESS USB INTERFACE

The Cypress USB interface is the core of the system, including
all of the necessary functionality to convert USB commands
into corresponding I 2 C or SPI read/write transfers, and acts as a
FIFO to route data between the host PC and the target device.

CRYSTAL OSCILLATOR

The Cypress USB interface is its own clock master, and the board
includes a crystal oscillator circuit with a 24 MHz crystal
resonator to provide stability to the oscillator circuit. The
crystal resonator is driven by the XTALOUT and XTALIN
pins of the Cypress USB interface.
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