I have a serial module, and the following happens…
I need to find out what is the right byte at the end of the string that is sent, this byte is changed accordingly which changes the value that will be sent to the module.

Data1 = 131.108.206.101
String: ATYS595300000000000000000002010017235345525649503D3133312E3130382E3230362E313031E10D0A
Data2 = 131.108.206.231
String: ATYS595300000000000000000002010017235345525649503D3133312E3130382E3230362E323331E50D0A
Data3 = 85716
String: ATYS59530000000000000000000201000B23465245513D3835373136530D0A
Data4 = 3600
ATYS59530000000000000000000201000A23465245513D33363030100D0A

Remembering that it is the byte preceding 0D0A, it is just 1 byte in which I cannot identify what it is.

I tried several types of calculations to try to identify the final byte, before 0D0A.
Unfortunately I couldn’t identify it, I need help.