Srec_cat - Multiple Values problem trying to insert CRC into binary file

Question

I am trying to calculate a CRC and insert in into the file at a fixed location using the following. I want to calculate the CRC over the entire file and then insert it at 0x1EC (1EC will be 0x00000000 in the image before the CRC is inserted):

srec_cat .\STM32F107RCT7-application.bin -binary -STM32_Big_Endian 0x1EC .\STM32F107RCT7-application.bin -binary -o outfile.bin -binary

But I keep getting the following error:

srec_cat: .\STM32F107RCT7-application.bin: 0x156BC: multiple 0x000001EC values (previous = 0x5A, this one = 0x00)

I think I somehow need to tell it to use the CRC value for this location but not sure how?

Answer 1

The normal way to do this is to calculate the CRC as normal, then cycle the CRC backwards by ((file length) - 0x1EC). An optional way to cycle the CRC backwards would be to multiply it by a negative power of 2 modulo the CRC polynomial using carryless multiply.

The only example of mine that I could find uses a carryless multiply intrinsic:

https://stackoverflow.com/a/70729922/3282056