S7-315 to RS232 ASCII

[Joe E.]

I have an application where I may have to be sending commands from a CPU 315-2PN/DP (6ES7 315-2EH14-0AB0) to a Hitachi PX-D26OU ink jet printer. From a quick read of their manual, the printer uses an ASCII protocol over RS232C. I have a little experience dealing with RS232 protocols using LabWindows to write code in ANSI C to send commands to RS232 devices, but I've never set up a device on Profibus from scratch like this. Has anyone else here encountered a similar application? How did you solve it? I came across the Anybus Communicator, which indicates that it can connect an RS232 device to a Profibus network. The PLC has a Profibus network with the PLC, 2 servos, and 2 I/O nodes. Anyone here have any experience with these?

[Joe E.]

Our Siemens distributor has pointed us to another option: the 6ES7 340-1AH02-0AE0, which is their CP340 communication processor with RS232C. I've tentatively added both the AB7000 and the CP340 to my hardware configuration for the fun of it. Both look fairly straight forward. If they're both reasonably available, we'll probably get both and see which is easier to use.

[ianbuckley]

We have used the Anybus Profibus to RS232 and the CP340. They both work fine, but there are differences in the approach. There are existing FBs to use for the CP340 and the documentation is okay. The Anybus has a separate programming package, but it is pretty simple to figure out. Personally, I would say which to use depends somewhat on how many pieces of information you have and whether the communication is mission critical. The CP340 is just RS232 ASCII, so if the cable is unplugged, the user program must decide how much you care and what to do about it. The Anybus is on Profibus, so it treats the device as I/O. So if the Profibus cable is unplugged, you have a system I/O fault. There is the additional cable from the Anybus to the printer, which also requires error checking if you care whether the communication link is active. The Anybus is better suited for a setup like an I/O table (or data that you want to collect from a table of settings) from my experience. The CP340 is better for strings where the length of the message changes, which seems a more natural fit for a printer to me, but that is just my two cents. HTH, Ian

[Joe E.]

OK, that's good info. I got in touch with an engineer at Anybus and discussed our application a little. From what he said, we would pre-program up to 50 strings and use the Profibus interface to tell the communicator which string to send to the printer. This will work for us, but we may want to be able to change the string at run-time, which it looks like we wouldn't be able to do. I have both modules on order and will experiment to see which one works better for what we want (and which one we can get working the fastest).