Click here to go to previous pagePLC Remote Programming


In a normal application of VISUAL, you usually will have a computer running LINUX in or near to the machine. The computer is connected to the PLC and to your intranet. The connection to the PLC is in many cases over the same connector the programming software uses. As all programming software I know is for Windows only, there is no easy solution for remote programming.
But here is a way to use the intranet connection for remote programming. It uses the programs serialProxy and serialClient coming with VISUAL:
It involves 3 computers :-(
The first is the one at the machine: Stop VISUAL, start serialProxy.
A second LINUX Box in your office runs serialClient and connects to the first.
Now connect the third computer running Windows and the programming software with a nullmodem cable to a serial port of the LINUX box.
The Windows box sends on it's serial port the characters it would send to your PLC. SerialClient receives these characters on the LINUX box's serial port and sends them to the computer at the machine over TCP/IP. Here, serialProxy receives the characters and forwards them to the PLC. The PLC's response is then transported back in the other direction.
This method has been successfully tested with Simatic S7-300 and Siemens Step 7 programming software. I hope it will work for other cases also. Note that, as only characters are transmitted, no hardware handshake can be used. The line parameters on both sides must be set to appropriate values at program start.
Examples:
serialProxy port=11777 '/dev/ttyS0 38400 o 8 1'
serialClient 192.168.17.110:11777 '/dev/ttyS0 38400 o 8 1'
or serialClient 192.168.17.110:11777 '/dev/ttyS0 38400 o 8 1' logfile
If you specify a logfile name, all communication will be logged to this file.
Another possible application case is to develop and test your application of VISUAL on a LINUX computer in your office. To do this run serialProxy on the remote (machine's) computer. Run VISUAL on the office computer. Instead of the usual driver configuration line for serial ports
driver: s7mpi.so mylist.tfi /dev/ttyS0 38400 o 8 2
write:
driver: s7mpi.so mylist.tfi tcp 192.168.17.110 11777 client
This tells VISUAL to open a TCP connection to port 11777 of machine 192.168.17.110 and use this connection instead of the serial port.