DLP-TXRX USB / SERIAL ADAPTER
DLP-TXRX
5V
USB Type 'B'
Mini connector
to Host PC/
Linux/Mac
93C46
EEPROM
VCCIO
IO Voltage Select
Jumper
VCC
USBDP
USBDM
TX
RX
VCCIO
5
External VCC
3.0 - 5.25V
User uC, uP,
DSP, FPGA
Reset
1
2
RXLED
TXLED
DTR#
10K
4
R
6MHz Resonator
FTDI FT232BM
3
1.0 Introduction
The DLP-TXRX USB-to-serial adapter is designed to easily connect a
microcontroller/DSP/FPGA/etc to a host PC; or upgrade a legacy RS232 device to USB
via a 2-wire serial interface with minimal design effort. Virtual COM Port (VCP) drivers
are provided royalty-free that make the DLP-TXRX look like a standard
Windows/Linux/Mac RS232 port to the user’s host program.
The old way...
TX
DB9
Level Shifter
RX
User uC, uP,
DSP, FPGA
The USB way!
USB Type 'B'
Mini connector
to Host PC/
Linux/Mac
TX
DLP-TXRX
RX
User uC, uP,
DSP, FPGA
Rev 1.2 (Sept 2004)
1
DLP-TXRX DLP Design, Inc.
1.1 Features Summary
• Royalty-free Virtual COM Port drivers
VIRTUAL COM PORT (VCP) DRIVER SUPPORT FOR:
• Windows 98 / 98 SE / 2000 / ME / XP
• Windows CE**
• MAC OS-8 and OS-9
• MAC OS-X
• Linux 2.40 and greater
[ ** = In planning or under development ]
• As few as 2 wire serial interface (RX, TX and ground)
• Standard baud rates from 300 to 921,600 baud
• Support for non-standard baud rates
• One open-collector output (pin 4): can be used for resetting microcontroller under
software control (DTR)
• Input provided (pin 5) for user-selectable interface voltage
• Red and green LEDs to indicate transmit and receive activity
• USB 2.0 interface compatible
• USB Description strings, VID and PID configurable in on-board EEPROM
• EEPROM Configurable in-circuit via USB
• Support for the RS232 BREAK setting and detection conditions
1.2 General Description
All operational power for the DLP-TXRX is taken from the host PC USB port or
upstream hub. All power required by user electronics must be provided by external
power supply.
FTDI provides a royalty free Virtual COM Port (VCP) driver that makes this USB device
appear as a standard COM port to the PC. Most existing software applications should be
able interface with the Virtual COM Port simply by reconfiguring them to use the new
COM ports created by the driver. Using the VCP drivers, an application program would
communicate with the DLP-TXRX in exactly the same way as it would a regular RS232
COM port - using the Windows VCOMM API calls or a COM port library.
Also available is a DLL version of the drivers that allows application programmers to
interface software directly to the device using a Windows DLL. Both the VCP and DLL
version of the drivers are available for download from both the dlpdesign.com and
ftdichip.com web sites.
The on-board 93C46 EEPROM can be used to customize the USB VID, PID, Serial
Number, Product Description Strings and Power Descriptor value of the DLP-RXTX for
OEM applications. The EEPROM is programmable in-circuit via USB using a utility
program available from both www.ftdichip.com and www.dlpdesign.com.
Rev 1.2 (Sept 2004)
2
DLP-TXRX DLP Design, Inc.
1.3 DTR Open Collector Output
Pin 4 of the DLP-TXRX is an open-collector output that is controlled by the DTR#
output of the FT232BM. Upon power up of the DLP-TXRX (i.e. when connected to the
host PC), pin 4 is initially driven low via an open-collector transistor until the host
application opens the COM port that the DLP-TXRX is assigned to. Once the port is
opened, pin 4 becomes high-impedance. From this point forward, the state of pin 4 can
be changed under software control via the user’s application program by setting and
clearing DTR#.
NOTE: if pin 4 is used to reset an external microcontroller, then upon power up the
processor will not run until the COM port is opened by the host application.
1.4 VCCIO Input
Pin 5 is used to provide power to the I/O pins of the FT232BM in instances where the
external microcontroller/DSP/FPGA/etc is operating at a voltage other than 5 volts. The
acceptable input voltage range on Pin 5 is 3.0 to 5.25 volts. If the external processor is
running at 5.0 volts then Pin 5 can be left disconnected.
If the external processor is running at a voltage other than 5 volts then the solder bridge at
location ‘5’ on the DLP-TXRX pcb must be removed and a solder bridge at location ‘3’
must be applied in order for the voltage applied to pin 5 to be used.
Rev 1.2 (Sept 2004)
3
DLP-TXRX DLP Design, Inc.
1.5 Activity LEDs
Transmit and receive LEDs are provided to indicate activity. When data is being
transmitted or received, the respective LEDs illuminate in order to provide indication of
data transfer. Circuitry in the FT232BM ensures that even a small percentage of data
transfer is visible to the end user.
Rev 1.2 (Sept 2004)
4
DLP-TXRX DLP Design, Inc.
2.0 Mechanical Dimensions
Inches (mm)
>>> Preliminary <<<
1.85 typ.
(47.0 typ.)
0.55 typ.
(14.0 typ.)
2.20 typ.
(55.9 typ.)
0.28 typ.
(7.1 typ.)
.035 x 5
(0.9 typ.)
0.23 typ.
(6.4 typ.)
Rev 1.2 (Sept 2004)
5
DLP-TXRX DLP Design, Inc.
