Not really a write-up, but the original source code, tools used to built the challenge and the ... DSP simulator ;)
[https://github.com/GreHack/CTF-challs/tree/master/2018/Reverse/300%20-%20Forgotten_Hardware](https://github.com/GreHack/CTF-challs/tree/master/2018/Reverse/300%20-%20Forgotten_Hardware)