checksum calculation ?

[jit_singh_tara]

how to do checksum calculation for 4 bytes say:

0x25,0x62,0x3f,0x52 , and verify it at the receiver....?

 

[alexz]

Just add them all and send the result to the receiver.
Add every byte you receive at the receiver and then verify the received checksum

 

[btbass]

A simple but effective checksum is two's compliment.
Sum all the bytes, disgarding the overflows, then compliment the final result and add 1. (twos compliment)

At the othe end, add the bytes to the checksum, disgarding the overflows, the result should be 0.

 

[aupa]

0x25 + 0x62 + 0x3F + 0x52 = 0x118

low byte --> 0x18

and now just use 2's complement. (invert all bits and add 1)

0x18 = 0001 1000 b

inverting
1110 0111 b

adding one

1110 1000 b

So the checksum is 0xE8

 

[btbass]

Checksum 0xE8

0xE8 + 0x25 + 0x62 + 0x3F + 0x52 = 0x00.