I am new to the Raspberry Pi, and haven't written much code for any computer in a long time. I have, in the past, written programs for my employer for serial interfacing, but that was long ago, and written in QBasic. I currently need to create a replacement for an old system that has multiple serial ports (10 - 22 ports) and multiple digital and analog I/O inputs. I am planning to use a Raspberry Pi to do this, but need to find out what it will take to do multiple serial ports on the RPi. A multi-serial to USB converter would seem to be best, but I'm not sure which one(s) might work with the RPi and how to get an interface to it going (since, unlike windows/DOS, I don't imagine the RPi is going to just assign a sequential serial number to a new port) For the digital I/O I'm using the Opto-22 modules, which are the descendants of the ones in the current ancient system we're using. (That system runs DOS 3.3 on an ancient Prolog computer with the STD bus. The program it runs was created in Basic by one of our employees around 20-25 years ago. We have 100 or so of these systems in service.)
Can someone give me some insight into what it will take to implement 8 or more serial ports (via multi-serial to USB converter) on the RPi? I have Raspian on the RPi and plan on using Python but I'm open to suggestions. I'd use Basic just because of my familiarity with it, but that seems rather outdated and I don't imagine Tiny Basic on RPi would be up to the task anyway.
Thanks for any help here.