Really cool idea combining TI-BASIC with physical hardware — I’ve played around with Asm(prgm for better timing too. For your case, an interrupt-based timer would be perfect. Just split it into two routines: one to start, and one to stop and display the time.

You might want to browse old projects on Omnimaga — lots of great TI-84+ assembly snippets there. Keep in mind: precise linkport timing needs tight instructions and minimal logic on the BASIC side. Great work and awesome that you’re inspiring your students this way!