Ignoring the first 4 bytes of the reply, it's an additive 8-bit checksum. Sum the bytes and mask the bottom 8 bits.
using the second block as an example:
data = [137, 8, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255] checksum = sum(data) & 0xff
-- Brian
On Mon, Mar 13, 2017 at 6:06 PM, Aaron Pelly via chirp_devel chirp_devel@intrepid.danplanet.com wrote:
On 14/03/17 14:01, Jim Unroe via chirp_devel wrote:
I am working on support for the Retevis RT23. I've captured a serial download. I've even successfully downloaded a "factory" image from the radio. But after looking at the data blocks, it appears that there is a checksum at the end of each block of data.
Can't help right now but here are a couple of links that might put you on the right foot:
https://sourceforge.net/projects/reveng/?source=navbar http://sitsec.net/blog/2012/02/10/brute-forcing-crc-parameters/
chirp_devel mailing list chirp_devel@intrepid.danplanet.com http://intrepid.danplanet.com/mailman/listinfo/chirp_devel Developer docs: http://chirp.danplanet.com/projects/chirp/wiki/Developers