USB to Serial
Reference Design
With the growing popularity of USB as the method of choice for connecting peripheral devices to
the personal computer, manufacturers are moving towards phasing out the legacy ports on PCs.
Companies producing devices that use the RS-232 interface for exchange of data will soon have
to find a new solution. Instead of altering the hardware design, application software and host
drivers for a current design, consider the option of a drop-in replacement for the existing RS-232
interface. Cypress offers a complete solution for replacing a legacy serial interface with USB on
an existing or new product – with an easy migration path to a true USB device.
The USB to Serial Reference Design is a single chip solution for seamlessly upgrading a serial interface to USB.
On the host side we provide a custom Windows driver that provides serial port emulation. The driver can
simultaneously emulate multiple RS-232 ports and allows complete control over the full range of baud rates, data
byte lengths, stop bits and parity bits.
On the peripheral side, firmware is provided for different USB microcontrollers to support a range of application
throughput needs. The enCoRe parts support lower data rate applications while CY7C64013 handles higher data
rate applications.
We provide source code for all of the firmware and a Design Notes document describing the system architecture.
Additionally the design includes Windows based applications for driver installation, serial data transmission testing
with the driver, and peripheral testing without the custom driver. Cypress provides faster time-to-market and the
lowest overall system cost with our USB to Serial Reference Design.
COM port emulation driver
No change to host application interface
Compatible with HID class driver
Easy migration to completely legacy free device
Single chip solutions
Reduces board space
Minimizes total cost
Multiple chips supported
! enCoRe: 600-56K baud (800 bytes/sec)
! CY7C64013: 600-56K baud (4K bytes/sec)
Match solution to cost and throughput needs
Supports RI, CD, RTS, CTS, DTR, and DSR
control and monitoring
Full control of baud rate, data bytes, stop bits and
parity bits
Compatible with legacy interface
USB 2.0 Specification Compliant
All software is compatible with industry standards
for low and full speed devices
Passes USBCheck 3.2 Chapter 9, Chapter 11,
and Hidview tests
Compatible with industry certification standards
Windows based test applications provided
Allows flexibility in testing of complete system or
peripheral only
Driver support on Windows 98, 2000, Me, XP
Robust operating system support
Driver Installer application
Streamlines installation and reduces errors
Minimizes support requirements
For ordering information contact your local sales representative.
Call toll-free in the US (800)-858-1810, or visit our web site at
Migration path from
RS-232 to USB
Host PC
serial port
serial port
Phase 2: The design allows
stratightforward migration to the
HID class driver supplied with the
operating system, thus removing
the need for custom driver support.
Requires modification of existing
software to communicate with a
USB device instead of RS-232
RS-232 cable
USB to serial with Cypress
USB Microcontroller
COM: port to USB driver
USB cable
Phase 1: Transition quickly to USB with
the Cypress USB to Serial design.
Can be used as a long term
solution if desired.
Phase 3: Alter hardware architecture to
communicate directly with USB
chip in most efficient manner
possible. Removes potential
limitations of a serial interface.
The USB to Serial Reference Design kit is a complete resource for developers to utilize and customize in the
development of their own product. Each kit includes:
Complete documentation
! Design Notes for enCoRe and CY7C64013
! Quick Start Guide
CD-ROM containing:
! Firmware source code
! Documentation
Serial port emulation driver
Test applications
Driver installation application
Visual Basic example
Note: Modifications to the firmware will require the appropriate development kit and the necessary programming
hardware. Please refer to the Cypress web site for a cross reference table of the appropriate hardware.
CY3654 – Platform Board
CY3654-PO5 – Personality Board
CY3654 – Platform Board
CY3654-PO3 – Personality Board
Note: Untested sample firmware for the EZ-USB family is also included on the reference design kit CD-ROM.
This firmware is compatible with the USB to Serial driver. It is provided as-is and can be used as a starting point
to develop a serial device based on these parts.
For ordering information contact your local sales representative.
Call toll-free in the US (800)-858-1810, or visit our web site at