Can anyone manage to work out how the checksum is calculated in the following data? Have tried reverse engineering crc and xor and anything else I can think of. There is a definite pattern there, but I cant work it out.
C8 00 02
DD 01 02
53 02 02
CC 03 02
BF 04 02
65 05 02
57 06 02
FE 07 02
35 08 02
44 09 02
28 10 02
3D 11 02
B3 12 02
2C 13 02
5F 14 02
85 15 02
B7 16 02
1E 17 02
D5 18 02
A4 19 02
27 20 02
32 21 02
BC 22 02
23 23 02
50 24 02
8A 25 02
B8 26 02
11 27 02
DA 28 02
AB 29 02
39 40 02
2C 41 02
A2 42 02
3D 43 02
4E 44 02
94 45 02
A6 46 02
0F 47 02
B5 49 02
D9 50 02
CC 51 02
42 52 02
DD 53 02
AE 54 02
74 55 02
46 56 02
EF 57 02
24 58 02
55 59 02
D6 60 02
C3 61 02
4D 62 02
D2 63 02
A1 64 02
7B 65 02
49 66 02
E0 67 02
2B 68 02
5A 69 02
05 80 02
05 80 02
10 81 02
9E 82 02
01 83 02
72 84 02
A8 85 02
9A 86 02
33 87 02
F8 88 02
89 89 02
E5 90 02
F0 91 02
7E 92 02
E1 93 02
92 94 02
48 95 02
7A 96 02
D3 97 02
18 98 02
69 99 02
3E 0A 02
AC 0B 02
17 0C 02
BE 0D 02
AB 0E 02
DF 0F 02
DE 1A 02
4C 1B 02
F7 1C 02
5E 1D 02
4B 1E 02
3F 1F 02
3F 1F 02
D1 2A 02
43 2B 02
F8 2C 02
51 2D 02
44 2E 02
30 2F 02
CF 4A 02
5D 4B 02
E6 4C 02
4F 4D 02
5A 4E 02
2E 4F 02
2F 5A 02
BD 5B 02
06 5C 02
AF 5D 02
20 6A 02
B2 6B 02
09 6C 02
A0 6D 02
B5 6E 02
C1 6F 02
F3 8A 02
61 8B 02
DA 8C 02
73 8D 02
66 8E 02
12 8F 02
12 8F 02
13 9A 02
81 9B 02
3A 9C 02
93 9D 02
86 9E 02
F2 9F 02
EA A0 02
FF A1 02
71 A2 02
EE A3 02
9D A4 02
47 A5 02
75 A6 02
DC A7 02
17 A8 02
66 A9 02
1C AA 02
8E AB 02
35 AC 02
9C AD 02
89 AE 02
FD AF 02
The first item on each line is the checksum. Much appreciated!!!
I have looked further into the left and right nibble of the second byte (the last byte is unchanged at 0x02). There seem to be repeated patterns depending on the values which I highlighted in Excel:
The colours highlight where there is repeating values. Not sure if this helps!
Further testing I am pretty sure this isn't CRC based. Starting with the first value of C8, as the first nibble changes from 00 to 10, the checksum goes to 28, which is the value XORd with E0. This holds up between 01 and 11, 02 and 12, 03 and 13... it is the previous value XORd with E0. So:
C8 00 02 XOR with E0
28 10 02
DD 01 02 XOR with E0
3D 11 02
53 02 02 XOR with E0
B3 12 02
However,
28 10 02 XOR with 0F
37 20 02
3D 11 02 XOR with 0F
32 21 02
B3 12 02 XOR with 0F
BC 22 02
And:
27 20 02 XOR with 1E
39 40 02
32 21 02 XOR with 1E
2C 41 02
BC 22 02 XOR with 1E
A2 22 02
Thanks again.
