CPU2: XMEGA 32A4U MH1710 KOREA-AB 35965E A88P8A - Main PCB, This is on the key and USB board
OK, that's new info. I'm not going back to check, but I suspect that the link I gave you that discusses decoding the file is for a different target in which case it's clearly not relevant. An ATMEGA disassembler might make some sense of that binary, but the important thing is that it's not something simple like a Python script which is immediately readable.
Sure, I could build and program my own measuring trolley, but now I want to get to this so that other model railway hobby practitioners can also get much more out of this wagon as it is already on the market.
Which is likely to mean new electronics as a drop-in replacement.
How hard would it be to write a program that listens to the raw data from the cart?
What I need to tell the program is the IP number that the cart has for the rest is known from WireShark:
UDP on port 55555.
Well, you've got the Wireshark captures. My own recollection from looking at them in the past is not very easy... at the very least I think you're going to need to make a "rolling road" arrangement so that you can move the wagon at a simulated controlled speed, simulate different cambers and so on.
Seriously. Your best bet is going to be to look at how that wagon is put together, and work out whether you could both make a drop-in replacement for existing wagons and apply the same thing to a new design... providing that you use cleanroom code you're probably legally OK. Oh, and for this you probably want to use TCP, unless you're pretty confident that your code is handshaking at a higher level.
Railways have used dynamometer cars since the C19th, and I'd remind you of Babbage's story of helping out when the only way to check the track was to release a wagon and time how long it took to stop (in his case, he arrived at the next station after jury-rigging a sail). There's almost certainly a niche market for somebody who can convert a wagon in a customer's chosen livery into an effective dynamometer, and being in control of the physical side of that would probably be adequate to protect against flagrant reuse of any code you choose to open-source.
Go for it man, and remember that if you don't there's multiple people in here that might see a viable opportunity... and many more reading courtesy of Google.
MarkMLl