The main cause why I have designed my own circuit, was bad circuitry style of RS232/TTY converter on www.runmode.com . It is not isolated
with optocuplers, and this could be dangerous for PC or for PLC in some situations. When I soldered converter from www.runmode.com, I
understood, that this is working, but absolutely not what I want to work with S5. So I designed my own circuit in simple and absolutely legal style. Feel free to mail me privately, if you need converter, designed in very strongest and legal engineering style, without compromise.
the RS232/TTY converter you found at "runmode.com":http://www.runmode.com has not been designed by me, but I used it with success for some years (well, maybe bricolage, but
effective). I agree perhaps it is not the best, it is a passive one and cannot be used to program intelligent modules (CP, WF, etc). Provided I'm not an expert in electronics, I discarded some other circuits available on the web, most of them designed with pure transistors (no
optocouplers at all). The one you found at runmode provide an optocoupler on the TTY rx side, while on the TTY tx side it relies on the PLC port built-in optocoupler.
I'm interested in better solutions. If anybody designed a good RS232/TTY converter, tested it with success and want to make it available to others, I'll be happy to add a link in runmode.com pages.
I've seen a couple vacuum tube designs that worked well I'll look them up if you want. :^) Seriously, there were fairly "standard" circuits that worked well when all hobbyists had available were real TeleTypes. Am I correct in assuming that you are converting to/from current loop? If so, a check of back issues of EDN and some of the hobbyist magazines from the 70's should yield results. I had all kinds of this stuff at one
time, I'm afraid it's lost to the sands of time. I
still have a current loop DECWriter in the basement.
