Westermo RM-80 - Manual (Page 32)

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3.12 Serial Port Configuration
The RM-80 has an RS-232, and RS-485 port for serial communications. These ports may
be used for different purposes. The RM-80 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 RM-80 can be used as a PPP Server to connect the wireless Ethernet system to
serial devices via the RS-232 or RS-485 serial ports.
PPP Server enables a network connection to the RM-80 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 RM-80, users must configure the local IP address for the RM-80 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 proc-
ess called “Proxy ARP” is used to make the device visible on the network. In this process,
the RM-80 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 cor-
rectly you must explicitly map computer names to IP addresses in the “LMHOSTS” file
on your PC.
When in SETUP mode, the RM-80 PPP server is enabled. This may also be used to config-
ure 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 RM-80 in SETUP mode, fol-
low these steps:
1. On Network Connections in Windows XP, select Create a new connection
2. On the New Connection Wizard, click Next
3. Set up an advanced connection
4. Connect directly to another computer
5. Set PC as guest