jiunnyang, thanks for this project! This is something i will want to use soon in an upcoming project. I can't test at the moment, but i want to give you encouragement!
Q: Are you planning on any encryption or CRC verification of the image? (Maybe it is already there - i haven't looked at your code yet.
Thanks!
-iain
Yes, I have Implemented CRC for XMODEM and Checksum for S19.
About Checksum of the S19, please find the value, checkSumTmp, in s19.c.
About CRC of the XMODEM, please find the function call, GetCrc, in xmodem.c.