Chapter Three
Operation
Page 39
© April 2007
3.13
Serial Port Configuration
The 805U-E has an RS-232, and RS-485 port for serial communications. These ports may be
used for different purposes. The 805U-E offers three different serial functions which are PPP
server, Serial Gateway, and Modbus TCP to RTU server.
3.12.1 RS-232 PPP Server
The 805U-E can be used as a PPP Server to connect the wireless Ethernet system to serial
devices via the RS232 or RS485 serial ports.
PPP Server enables a network connection to the 805U-E over a serial cable. This is much like
dial up internet. The maximum serial data rate is 38.4Kb/s. Hardware or Software flow
control may be selected.
With minimal configuration on the PC, you may use Dial up networking in Windows XP to
connect to the network via the serial port.
For the 805U-E, users must configure the local IP address for the 805U-E and the remote
device IP address. Some care must be taken in selecting these IP addresses.
If you wish to use routing over this serial network connection, then the IP addresses selected
must not lie on Wireless or Wired Ethernet networks already configured into the device. You
must ensure they set routing rules appropriately for devices either side of the network.
If you want the serial device visible as present on the Wireless or Wired network, then the
local IP address must be the same as the IP address set for the desired port. A process called
“Proxy ARP” is used to make the device visible on the network. In this process, the 805U-E
pretends that it holds the IP address on the network, and responds on behalf of the remote
device.
The result of this is similar to bridging for a single device, with some exceptions. One of
these exceptions is the inability to handle name server searches of the network via this serial
link. For example, you would encounter difficulty if you were to use Windows Explorer over
the serial link to find a PC on the wired network. For this to operate correctly you must
explicitly map computer names to IP addresses in the “LMHOSTS” file on your PC.
When in SETUP mode, the 805U-E PPP server is enabled. This may also be used to
configure the module. Settings whilst in SETUP mode are as follows:
•
username user, password is user.
•
Serial baud rate 38400bps
•
Hardware flow control
•
Local address 192.168.123.123
•
Remote address 192.168.123.124
To configure Windows XP to establish a PPP connection to a 805U-E in SETUP mode,
follow these steps:
