GridConnect BF-850 User Manual
Grid Connect Revision A, 6/2/11
BF-850
USB/RS-485/RS-422 Converter
User’s Manual
1.0 General introduction
In a fast developing PC industry, the USB interface is
replacing many old PC serial interfaces one step at a time.
However, many types of important equipment still use
RS-422/RS-485 interfaces in order to transfer data. This is why
there is need for the USB/RS-422/485 converter.
The BF-850 is a commonly used type of converter. It is
powered from the USB interface of a PC and does not need any
external power source. It also conforms to the USB, RS-422 and
RS-485 standards. There is no delay and the signal is converted
automatically inside the device. The unique I/O auto-controls
the direction of data transfer, and needs no handshake signals (like
RTS or DTR) to transfer with full duplex (RS-422) and half
duplex (RS-485).
The BF-850 can provide a reliable connection with point to
point and point to multi-point data transfer. In point to multi-point,
each converter can connect up to 32 units of RS-422 or RS-485
interface. The speed of data transfer is between 300 and 921600
bps and the communication types are USB to RS-422 or USB to
RS-485.
2.0 Performance parameter
1. Standard：
Conform to the standards of USB V1.1, EIA RS-485, and
RS-422.
2. USB signal：
VCC, DATA+, DATA-, GND, FG
3. RS-485 signal：
T+, T-, GND
4. RS-422 signal：
T+, T-, R+, R-, GND
5. Communication type：
Asynchronous communication, point to point or point to
multi-point, 2 lines of halt-duplex, and 4 lines of
full-duplex.
6. Communication control：
Uses auto-control technology to transfer data and
automatically determines and controls the direction of data
transfer.
7. Baud Rate：
300~921600 bps, automatic detect the serial port speed.
8. Load ability：
In point to multi-points each converter can connects 32
units of RS-422 or RS-485 interface equipment.
9. Communication distance：
RS-422/RS-485 5000 meter (9600 bps), USB less than 5
meter
10. Type of communication line：
Double twist line or cover line.
11. Communication speed：
921600 bps 300 M 38400 bps 2.4 KM 9600 bps 5 KM
12. Dimension：
55mm × 36mm × 18mm
13. Operation environment：
-25 ~ 70℃℃, humidity 5% ~ 95%
14. Operating Systems
Windows95/98/2000/XP/Vista/7
3.0 Connector and signal
RS-422/RS-485 export signal
DB9 PINS
Output
RS-422
Duplex
RS-485 Half
Duplex
1 T/R+ Transfer(A+) RS-485(A+)
2 T/R- Transfer(B-) RS-485(B-)
3 RXD+ Receive(A+) Empty
4 RXD- Receive(B-) Empty
5 GND Ground Ground
6 N/A
7 N/A
8 N/A
9 N/A
4.0 Installation setup and application
The BF-850 uses a USB/DB-9 connector and needs no
crossover cable. T/R+ and T/R- represent transfer and
RXD+/RXD- represent receive. GND represents the public
ground line.
The BF-850 provides 4 types of communication as below：
1. Point to point/4 lines full-duplex
2. Point to multi-point/4 lines full-duplex
3. Point to point/2 lines half-duplex
4. Point to multi-point/2 lines full-duplex
Half-duplex (RS-485)
Connect the 2 lines to T/R+ and T/R-
Full-duplex (RS-422)
Connect the 4 lines to T/R+, T/R-, RXD+ and RXD-
When connecting full-duplex or half-duplex, in order to
prevent reflection or interference of the signal, you need to
connect a resistance at the end of line (120Ω 1/4W).
Grid Connect Revision A, 6/2/11
5.0 Sketch map for communication connection
USB/RS-422 transfer
5.1 RS-422 point to point 4 lines full-duplex communication
5.2. RS-422 point to multi-point/4 wire full duplex
5.3. Full duplex communication connection between
GC-BF-850 interface converters
USB/RS-485 transfer
5.4 RS-485 point to point/ dual-line half duplex
5.5 RS-485 point to multi- point /dual-line half duplex
5.6 Half duplex communication connection between
GC-ATC-107N interface converters
6.0 Trouble shooting
7.1 Data transmission failure
A. Check to make sure the USB interface is correctly connected
B. Check to make sure the RS-422/RS-485 interface is correctly
connected
C. Check to make sure the terminal connections are correct
7.2 Data loss or error
A. Check the consistency of the data speeds and formats at the
both ends of the data communication device.
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