I have an obsolete control system that I am trying to write an interface into our new control system. I have spent weeks capturing data and figuring out the addressing, polling commands, point addressing and payload. I have everything figured out except on how to calculate the checksum on the packets. Below is a small sample of the data - I believe the first 2 bytes are the checksum, bytes 3/4 - address, bytes 5/6 - command, remaining bytes are the payload:
0e00 0801 1280 //to controller 0e20 //from controller 0e10 0801 1200 8010d00d9b0a19120a27375f01010412071f0e0a0512aa10495349474854000000000000000000000000000000000000000000001400ff0e0e00000000 //from controller 0e40 //to controller 0f00 0801 1285 //to controller 0f20 //from controller 0f10 0801 1200 0000000000000000000000000000000001010a0512aa105f1400ff //from controller 0f40 //to controller 1000 0801 1285 //to controller 1020 //from controller 1010 0801 1200 0000000000000000000000000000000001010a0512aa105f1400ff //from controller
The checksum appears to be out of order when viewing the data captures, but that is the order that it was captured in.
I don't know if it matters or not, but I am writing the interface in Java.
I appreciate any help that can be provided ... many thanks in advance.