A while back I did a wired project that just used a byte add error checking method.

Add each byte to the last and store the sum in a byte sized variable:

RX var byte[10]
CHKSUMCALC var byte

For Cnt=0 to 8
HSerin 2,No_Data,[RX[CNT]] ' Buffer bytes to RX
CHKSUMCALC = CHKSUMCALC + RX[CNT] ' Calculate the checksum
Next Cnt