Move data from your old controller into a PAC - via serial connection RS232/RS485

Hi All,

Other peer-to-peer examples you’ll find on the forums provide various options for moving data via Ethernet, but what if you only have a serial connection, for example, to a really old controller?

Here’s how one of our long-time customers, with a big variety of Opto 22 hardware, started moving data into his PAC, using just a little logic. He’s got:

…controller running Factory Floor. The program is simple: I configure com1 (2 wire 485) with the configure port “com1:38400,n,8,1” and made a loop with a delay to Transmit table via serial port… an integer table with a length of 28.

On his PAC, he uses a comm handle, similarly configured, just looping to receive that same table.

Ta-da! Data from old controller now in PAC and read to groov! Of course, for data to be written, you could just add another chart to go the other way – with the PAC doing the Transmit and the FF Controller doing a receive. Easy as π (pi). :wink:


We had a setup at the hospital where we had another crude control system (that was slowly getting replaced by the Opto 22 system) that we had to exchange information with.

This other system did not have Ethernet, nor serial, but it did have analog inputs and outputs.
So what we did is hook up an analog out of Opto to an analog in on the other system and vice versa.

Now, with a little code on each end and with just three wires (two analogs and a ground) we could exchange a fair bit of information.
Each voltage level had a little buffer around it, but the end result was that would swap around 20-30 bits of info each way. (The Opto could do a lot more with its resolution, but the other system… did I mention it was pretty crude?).

Yeah, it was a little slow, but it was mainly for status, alarms and slow control in HVAC systems.

Worked fine for many many years.