Devlog #4
TOTP generation is working! The device is now showing real codes.

Getting here took more work than expected. TOTP sounds simple on paper but actually implementing HMAC-SHA1 correctly, handling Base32 decoding and making sure the time step calculation lines up exactly took a few attempts. I ended up getting help from Claude to do the implementation right but it works and now I understand how it fits together.

Next up is USB HID so pressing the encoder button actually types the code into whatever field has focus on the host.