DB9-USB-RS232 Datasheet, PDF (21/27 Pages) Future Technology Devices International Ltd. – DB9-USB-RS232 Module Male & Female

Document Reference No.: FT_000204
DB9-USB-RS232 Datasheet
Version 1.2
Clearance No.: FTDI# 130
8 Troubleshooting
Ensure the latest device driver is in use. See www.ftdichip.com
If USB devices other than FTDI chips are installed in the system, then check with all manufacturers of
these devices for the latest device drivers.
Section 3 details driver installation. If the user continues to have driver installation isues, then please
refer to the FTDI installation guides http://ftdichip.com/Documents/InstallGuides.htm for additional
details.
Common Windows Device Driver Troubles:
DEVICE TIMES OUT: The default settings of the device driver assume typical data transfers of
hundreds to thousands or more bytes at a given time. Some applications, such as a GPS device,
only send data in short packets, often only a few bytes. If this is the case, it may be necessary
to adjust the driver buffer size and/or latency timer to smaller values. These values can be
adjusted through the Advanced driver options. The buffer size can be reduced to 64 bytes. The
latency timer can be set as low as 2ms. A setting of 1ms will cause unnecessary USB traffic and
could adversely affect data transmission. Advanced driver options are described in
http://www.ftdichip.com/Documents/AppNotes/AN_107_AdvancedDriverOptions_AN_000073.pdf
ERRATIC MOUSE POINTER: The device driver defaults to query an attached device to find out
whether it is a mouse or modem, consistent with native COM port operation. Some RS232
peripherals constantly send short packets of data, causing the host system to “think” a mouse or
modem has been attached. These short packets will interfere with normal mouse operation
causing the pointer to jump around the screen. If this happens, disconnect the RS232 device and
uncheck the Serial Enumerator option, also found on the Advanced driver options.
COM PORT IN USE: Windows keeps track of all COM port assignments. If multiple FTDIChip
products have been connected to a single system, the COM port number will increase, even if the
other devices are not attached. If the higher COM port assignments are not acceptable for the
application, known unused COM port numbers should be uninstalled according to the FTDI
installation guide: http://ftdichip.com/Documents/InstallGuides.htm.
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