Interfacing 24VDC to 5VDC. How decent is my solution?

[Kjelt]

In almost all cases there will be a 3-phase VFD or inverter for DC motors in the same switching cabinet from what my device will be powered and controlled. Or big thyristor power controllers for high temperature furnaces. I expect, that in most cases the cable that provides power and input signals is not longer than 20-30 m.

I would consider that medium length cables in a noisy environment (depending on motor wattage) but I would recommend using an optocoupler and isolate the ground as suggested earlier.

[128er]

Here is what I have done until now. It's not finished yet. Some connections are missing, values wrong. And I defenitly want to minimize the number of code switches. At the moment there is one for each input, to decide which modules should be switched on.

[Kjelt]

Make sure you test and get the layout around that led driver correct. My experience three years ago with a Maxim led driver doing 700mA was that it needed an additional small filter because it jammed around the 100MHz (FM band).  not sure about this driver though, but is wort while testing before ordering large quantities of pcbs.

[Jeroen3]

You can turn those rotary selects into potentiometers with some resistors so you only need 1 ADC line per rotary, instead of 4.
Or you can multiplex digitally, then you only need 7 inputs. Or multiplex analog, with 1 adc and 3 digitals.
There is no need to give them up for the pincount.

[128er]

Make sure you test and get the layout around that led driver correct. My experience three years ago with a Maxim led driver doing 700mA was that it needed an additional small filter because it jammed around the 100MHz (FM band).  not sure about this driver though, but is wort while testing before ordering large quantities of pcbs.

That's a good advice. But in this case it's a linear LED driver. And I think the PWM signal to it, won't make any significant difficulties, too.

You can turn those rotary selects into potentiometers with some resistors so you only need 1 ADC line per rotary, instead of 4.
Or you can multiplex digitally, then you only need 7 inputs. Or multiplex analog, with 1 adc and 3 digitals.
There is no need to give them up for the pincount.

The pincount of the MCU is not a big deal. It's more about board space and minimizing the "user interface". And maybe minimize parts for cost. But I will think about the solution with the ADC as an input for the rotary switches. I have  done that with Keypads before.