LoveJoyDK wrote:Flexible: the system is not limited to ore, it can be used to ferry intermediate products, too, even on the same logical line with the ore trains.
I think that sendt me to fantasy lala land, fantasying about sending green circuits everywhere.

That's not fantasy land, that's possible. You can make a loader for circuits (at the circuit factory) and an unloader (at another factory that makes stuff with circuits), it's not different from ore and smelting of ore.
The major restriction right now is that you need to make the connection between load (provider) and unload (requester) in the setup of SmartTrains. So when you have multiple unloaders for the same product then there's no clean solution anymore (some hacks are possible, but nothing pretty and balanced).
Since you've already started thinking about the problem you see that it's not easy to solve (well at least not by adding, like, 3 combinators and be done).
Anyway, I am here as much to put my ideas in words, as much as to get them commented. I hope that is okay.
Yes. Half of what I write I actually write to myself, so I can understand the problem better and maybe read it 6 months from now when I will have forgotten what I did there...
I think I could use the locomotive signal to stop sending request for more ore, by subtracting the expected load of the outgoing train at the offloading station. Thereby make the calculation for ore need take into consideration the load in the train sendt out. But still have to figure out how to link it with the right ore type.
This is what I have in mind as well. The ore type should not be a problem because the unloading station knows what the ore type is. You don't need the information, only the amount.
Unless you have mixed goods unload, but that's a different ball game (I currently assume each unload can only request one type of item).
But you cannot use any of these signal (Locomotive, Rail Signal, ...) on the red bus in that way, because if you're unlucky you send it during the same tick as another outpost, and then the signals get added on the wire and it breaks. This is impossible to debug, because it will happen randomly.
If you run multiple protocols like this on the same wire they all need to use entirely different "alphabets", because otherwise collisions are always possible. It does not matter how rare they are, unless they are
astronomically unlikely you have to avoid them. (By "astronomically" I mean: so unlikely that you'd have to play for 1000 years to observe the event once or something like that.)
I have also considered making a green bus, instead of a red bus. And then make a coder/decoder circuit to put between the green bus and the depots/stations. By doing that I would leave your work intact. (Read: I know that work, and I have no mistakes to fix there.)

,
Currently I do not want to extend my system to require green wire as well, but if that opens a way to make it more powerful while keeping the simplicity I will do it. If you use FARL it makes no difference if you draw red wire or both red and green, it's automatic.
(Thinking about it, it's probably
dumb not to always draw red and green wire along all railways, because it costs practically nothing and it might be useful some day; replacing the wire after the rail network has become big is a lot of work.)
But I am unsure how to make sure everything stays on the same right tick of the counter. The signal one tick wide thingy.
If you look in this thread you will find a link that user kann_ has posted to his own creation on reddit. He's using a multiplexing protocol that involves a receiver (decoder), and he does have a link for that, too.
Putting the signal ore=2147483647 on the red wire bus, so it will be added to a responding ore=1 on the same tick, triggering the"IF anything = -2^31 THEN output everything".
Yes, that works, you can put it on the red bus like you described. However, if there are several unloads for the same ore, you cannot add the values together. For example, if you have 2x iron unload, and they both request iron ore, then the value still needs to be 2^31-1 in total, not 2x 2^31-1. So you need to combine the two signals with a circuit before putting them on the red bus.
What mods would be recommended for a semi test server.
I don't play on servers, but the mods are used are exactly those in the OP. In fact I use the demo map from this thread and the mods for all my experiments in Factorio right now.
There are some mods that I've skipped that are useful: JasonC has made a great mod for picking up items (like test mode but with much better UI), AutoFill is good too, maybe even some Bob's Mod stuff with faster belts and inserters and OP robots, large trains etc -- so you can test all the possibilities.