I'm working on a custom Access Control system for my local airport that will validate passengers' boarding passes and I've been given two DESKO GRSK 502 scanners.
Unfortunately, there's absolutely no documentation available on them and the manufacturer is not willing to disclose any information on how the scanners operate even though they reached End of Service in 2020.
I managed to find a script that is used to update its firmware and it appears to contain what I've been looking for.
I am a complete newbie when it comes to reverse engineering, so the only things I've managed to get from the firmware are some random command strings. Unfortunately, however, the scanner always returns a 'Negative Acknowledge' response, so I'm guessing it expects some initialization command before accepting any others.
Here is the firmware itself: https://pastebin.com/UDgne3Q8 I used Hex2Bin to convert the firmware file to a .bin file and the loaded it up on IDA Pro. Upon Googling, I came across this blog post which mentions that IDA Pro should be provided with the processor's ROM start address in order to decompile it properly.
Here's the inside of the scanner:
I assumed that the processors is 'P80C5521BA', but there's no information on NXP's website on its ROM start address.
I would appreciate any help I can get in extracting any information from that firmware file. 🙏