This week I finished my main goal of getting the PS2 protocol working and synthesized on the DE10! At the beginning of the week I debugged my own implementation of PS2, wrote and testbench and got the simulation working. However, I decided to pivot to modifying an existing PS2 protocol that I found online after realizing I was missing some of the handshaking signals in my current implementation.
I spent Tuesday debugging the online implementation and updating it to run on a DE10 (the old version was for DE2). On Wednesday, I was able to synthesize with only a few minor bugs! However, when testing with the Perixx PS2 keyboard we had ordered from Amazon, only the scan code “AA” was sent which means that the keyboard’s “Self Test Passed”. After looking at the user manual I realized that the PS2 port on DE10 was only providing 3.3V and the keyboard required 5V (oops). After looking at some PS2 reddit forums, it seemed like most people online agreed that old PS2 keyboards were compatible with PS2 ports of various FPGAs and the newer Perixx PS2 keyboards seemed to just not work.
We decided to go hunting on Facebook Marketplace for some old PS2 keyboards and Tanisha found someone selling 2 keyboards close to campus. Tanisha and I met the seller outside the CMU Police station on Friday and got two old HP PS2 keyboards for $15. The seller actually ended up refunding the cost as good luck for our capstone so it ended up being free! I went straight to lab and the FB Marketplace keyboard worked immediately! In the video below I just press a few keys on the keyboard and the scan code corresponding to that key is displayed on the FPGA’s seven segment display.
I spent Friday and today working on the actual enigma encryption. I based my code on some of the logic in this FPGA enigma machine and hardcored the rotor settings based on the 1930 ‘Enigma I’ model and the reflector on “Reflector B” from spring 1942. I got the encryption working in simulation today and verified my outputs with this online enigma emulator. Next week I hope to get this code synthesized with keyboard inputs and the rest of the inputs (rotor, ring, reflector) hardcoded.
This week I accomplished more than I had hoped and the RTL is coming along well! After synthesizing the encryption with the keyboard I’ll start looking into the microSD card RTL and rotary encoder FSMs.