db9-usb-rs232 Future Technology Devices International Ltd., db9-usb-rs232 Datasheet - Page 7

• Manufacturer Part Number: db9-usb-rs232
• Description: Rs232 Connection
• Manufacturer: Future Technology Devices International Ltd.

2.1.2 Replacing an RS232 DB9 MALE (DTE defined) Connector
The DB9-USB-RS232-M can be used to replace a male DB9 connector used for transmitting RS232
protocol. With the DB9-USB-RS232-M in place instead of the standard USB connector a USB bridge is
created, this allow the application to communicate with other devices via USB. Installing the DB9-USB-
RS232-M is simple. Simply replace the male DB9 connector with the DB9-USB-RS232-M connector (same
PCB footprint), install drivers and the device is ready to use.
Table 2.2 gives the pin out description of each pad of an RS232 footprint. Figure 2.2 gives a description
of the connections between the DB9-USB-RS232-M and the footprint of a male DB9 module.
Note 1:
with a null-modem wiring. The null-modem wiring allows DTE to DTE communications between the DB9-
USB-RS232-M and a standard DB9 male application board. However a DTE device is defined to have 5
inputs and 3 outputs, where a DCE (Data Communications Equipment) is defined to have 3 inputs and 5
outputs as in the case of the female DB9 application boards. This leads to a conflict in an DTE to DTE
connection application, This conflict is that there are more inputs to a connected USB-converter device than
there are outputs from the application board (and more inputs to the application board than there are outputs
of the USB converter). This conflict occurs on the DCD and RI connections and as such they cannot be
used. This issue is very common when translating RS232 to USB from a DTE perspective. Additional
information showing DTE and DCE wiring is given in Appendix B.
Figure 2.1 illustrates these connections from a PCB footprint point of view. Figure 2.2 Illustrates the
connection made to an example PCB.
Number
Shield
Pin
1
2
3
4
5
6
7
8
9
The DB9-USB-RS232-M is electrically configured to be a DTE (Data Terminating Equipment) device
USB-RS232 module
Pin Type of DB9-
Input (note1)
Input (note1)
Ground
Ground
Output
Output
Output
Copyright © 2010 Future Technology Devices International Limited
Input
Input
Input
Table 2.2 – A Male RS232 DB9 footprint Pin-Out
application PCB
Pin Type at
Case Ground
Ground
Output
Output
Output
Input
Input
Input
Input
Input
(this is an input to the DB9-USB-RS232-M
(this is an input to the DB9-USB-RS232-M
(this is an input to the DB9-USB-RS232-M
Drain = typically connected to the host PC
RS232-M to the application DSR input)
RS232-M to the application CTS input)
(this is an output from the DB9-USB-
RS232-M to the application Rx input)
(this is an output from the DB9-USB-
(this is an output from the DB9-USB-
from the application DTR output)
from the application RTS output)
from the application Tx output)
GND = RS232 signal ground
DTR = Data Terminal Ready
DCD = Data Carrier Detect
Document Reference No.: FT_000204
RTS = Request To Send
DSR = Data Set Ready
TXD = Transmit Data
CTS = Clear To Send
RXD = Receive Data
RI = Ring Indicator
Description
case
DB9-USB-RS232 Datasheet
Clearance No.: FTDI# 130
Version 1.2
6