USB-COM422-PLUS-2 FTDI, USB-COM422-PLUS-2 Datasheet - Page 20
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USB-COM422-PLUS-2
Manufacturer Part Number
USB-COM422-PLUS-2
Description
MODULE, DEV, USB-RS422, 2 COM PORT
Manufacturer
FTDI
Type
Developmentr
Datasheet
1.USB-COM422-PLUS2.pdf
(24 pages)
Specifications of USB-COM422-PLUS-2
Mcu Supported Families
FT232R, FT2232, FT232BM
Kit Features
Works With USB 1.1 & 2.0 Host And Hub Ports, FIFO
Svhc
No SVHC (18-Jun-2010)
2.0 Host And Hub Ports, Fifo
4KB Transmit Buffer, 4KB Receive Buffer
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
8
8.1
Cables are the most common sources of trouble with external devices.
Check the following:
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RS422 cables – check the following:
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8.2
Ensure the latest device driver is in use. See www.ftdichip.com
If other devices with FTDI chips are installed in the system, check with all manufacturers of these devices
for the latest device drivers.
See the FTDI installation guides for additional details:
Common Windows Device Driver Troubles:
USB cable is properly inserted at both ends
Computer power is ON
Computer is not in Sleep or Standby
If a USB Hub is used, be sure it is set for “Self-Powered” operation
If a USB Hub is used, be sure all cables are properly inserted
If all the above are OK, the Yellow LED should be lit, indicating the device has been recognized by the
USB subsystem.
Output signals (TXD+, TXD-, RTS+, RTS-) are connected to the respective inputs (RXD+, RXD-,
CTS+, CTS-) in each direction.
Check for specific handshake requirements of your RS422 peripheral.
If handshake signals are not used, ensure the application is set to “No Hardware Handshake”, or
equivalent.
Test the port with a loop-back connector. Connect TXD+ to RXD+, TXD- to RXD-, RTS+ to CTS+ and
RTS- to CTS-. Use a simple terminal program to check that data is transmitted and received.
Troubleshooting
Hardware
Device Driver
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 as noted in Figure 2.13. 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.
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 RS422
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 RS422 device and
uncheck the Serial Enumerator option, also found on the Advanced driver options screen in Figure
2.13.
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.
Copyright © 2010 Future Technology Devices International Limited
http://ftdichip.com/Documents/InstallGuides.htm
Document Reference No.: FT_000135
USB-COM422-PLUS2 Datasheet
Clearance No.: FTDI#103
Version 1.1
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