I've not used CRC but I normally add one checksum byte at the end of the data-packet, which is 2's complement sum of the all the bytes in the packet. At receiving end, the sum of all the bytes in the packet (including checksum byte) should be 0x00.
For example, if I'm sending 5 bytes/ packet, then add this 5 bytes without carry, then take 2's complement of the sum and attach it with the packet as 6th byte. At receiving end, add all the 6 bytes of the packet without carry, the sum should be 0x00. If the sum is not zero, ask for retransmission of the packet.