User guide

CY3687 MoBL-USB FX2LP18 Development Kit User Guide, Doc. # 001-68582 Rev. *B 17
3. Development Board
3.1 Introduction
The Cypress Semiconductor MoBL-USB Development Board provides expansion and interface
signals on six 20-pin headers. A mating prototype board allows quick construction and testing of
USB designs. The board may be powered from the USB connector or an external power supply.
Note that some of the signals driven by the MoBL-USB FX2LP18 device on the Advanced
Development board have been replaced by VCC-IO and 1.8 V supplies.
The MoBL-USB Development Board is supplied as part of the Cypress Semiconductor MoBL-USB
Development Kit, which includes an evaluation version of Cypress-customized software
development tools from Keil Software Inc. The Keil 8051 assembler, C Compiler, and debugger work
in concert with the development board to provide a complete code development environment. The
evaluation version of the Keil tools that ships with the DVK has several restrictions that make it
inappropriate for real-world development. Most significantly, it limits the compiled object size to 4 KB.
The full retail version allows code of any size.
3.2 Schematic Summary
This description should be read while referring to the MoBL-USB Development Board schematic and
the MoBL-USB Development Board Assembly drawing. Both drawings are attached to the end of
this document and are available in PDF format in the DVK hardware directory.
U3 is the MoBL-USB 56-pin device. Although there is a large (100-pin) FX2LP on the board (U11),
this chip is only used for I
2
C to serial translation, it is not available as a USB device.
Power to the MoBL-USB device comes from two or three different supplies. The AVCC pins draw
3.3 V through jumper JP4. The VCCCore supply requires 1.8 V, which it receives from JP2. The I/O
pins (VCCIO) can run on voltages ranging from 1.8 V to 3.3 V. JP10 provides the ability to select the
input voltage to VCCIO from the 1.8 V, 3.3 V or 2.5 V (adjustable) regulator.
U6, U9, and U10 provide power to the board. All of these devices can provide up to 500 mA, so there
is plenty of spare power on all of the supplies to handle any devices on the prototype board. The out-
put voltage of U9 can be varied by changing the ratio of R29 and R34. See the LT1763 data sheet for
more information.
U7 and U8 are socketed EEPROMS, used for MoBL-USB FX2LP18 initialization and 8051 general
purpose access. U5 is another EEPROM, used for factory initialization. This part is required because
the MoBL-USB chip starts up disconnected from USB and it requires an EEPROM load to connect to
USB. JP6 prevents this part from accidental programming.
U2 and U4 are Philips PCF8574 IO expanders, which attach to the MoBL-USB FX2LP18 I2C bus
and provide eight GPIO pins. U2 reads the four push-button switches S2-S5, and U11 drives the
seven-segment readout U1.