Rx validation of checksum

[archendekta]

CALC_Checksum1:
    Checksum1 = 0
    WORD_HOLD = 0
    for i = 3 to MAX_LEN
       Word_Hold = Word_Hold + tx_data1(i)
     next 
     Checksum1 = WORD_HOLD.byte0 ^ $FF
    RETURN

CALC_Checksum2:
    Checksum2 = 0
    for i = 3 to MAX_LEN
       Checksum2 = Checksum2 + tx_data1(i)
    next 
    Checksum2 =  Checksum2 // 256
   'Checksum2 = -Checksum2
    RETURN

the above routines i pieced together from other posts here to genereate a checksum for transimitted data packets.

to validate on the received end, do i run the same routine and compare values to see if the checksums are equal?

[Ioannis]

Yes you do.

But instead of this double checksum i'd prefer the 16 bit CRC check. More reliable.

Look here for the fast sub routine from the usual suspect:

http://www.picbasic.co.uk/forum/showthread.php?t=11790

Ioannis

[archendekta]

Thanks Ioannis.

Indeed, DT's looks quite fast. a handy routine i'll "borrow" into me tool box.

btw, i would use [either or] of my sub-routines, not both at the same time.

Cheers!