After looking at the Beremiz iec2c compiler source, I decided that modifying it to fit into this project is probably not the way to go. At this time, I’m deep into experimenting with the Coco/R framework on Java to produce my own IEC compiler. To make things simpler, I decided to support only ST language with some other limitations (only datatypes that can be directly mapped to Arduino/C++ native datatypes, single program, single task, etc.). The rest of this stuff could be added later without too much hassle.
Now it’s also clear what changes I will make to the hardware: I will put one optocouppled analogue and two optocouppled digital inputs on the input side and two relay outputs on the output side. No bus I/O extensions at this time. Also, the communication part (RS232 on hardware UART and virtual serial over chip’s USB) and it’s software implementation in firmware will remain as-is. These things would be, of course, the first things to change if we went on to make this thing look a bit more serious.
That’s it for now. I welcome any comment or thought.