This is a page where I link code that I have written that is publicly available. Most of my professional work has been proprietary, and I have not been much of a hobbyist programmer over my career (though I’m trying to change that), so unfortunately most of my code doesn’t make it on here, but there is still some!

My GitHub is jhartzell42.

There is also code published on various articles on this blog. Any code on this blog is covered under the MIT license.



  • ledger-app-tezos (professional, mostly 2018): Although I am not personally a cryptocurrency enthusiast, during my time working for Obsidian Systems, it was part of my job to implement this app to support Tezos on the Ledger. Though it was a group project, I was the primary original author. The original target platform, the Ledger Nano S, had only 4K of RAM. I understand it has changed a lot since I originally worked on it.
  • compass (hobby, 2009-2010): This was a hobby project with a friend in college, and it is a bytecode interpreter for a Smalltalk-like language in C, combined with a compiler in Python and an “assembler” for the bytecode language also in C.