erichdonahue.com

Selected Work

Music tool case study

Endless Loader

A local web tool that finds a connected Polyend Endless pedal over USB, writes a patch to it, and checks the write with a SHA-256 read-back before calling it done.

GitHub repository

What it is

Endless Loader is a small local web tool, meant to run on a Raspberry Pi or Ubuntu-family Linux box sitting next to the pedal rather than on my main machine. It finds a connected Polyend Endless over USB with lsblk --json and findmnt --json, mounts it with udisksctl if it is not already mounted, writes the .endl patch I picked, and then reads it back and checks the SHA-256 before it tells me the write actually worked. There is an fsync call in there too, because a write that looks done and is not is worse than no write at all.

Why I built it

Moving a patch onto the pedal by hand is a small, fiddly, repeatable task, which is exactly the kind of task I do not trust myself to do carefully every time. I wanted browse, choose, load, verify to be four clicks instead of a manual USB dance I would eventually get wrong. Config lives in one config.toml, with library_root pointing at where the patches live and expected_uuid naming the pedal’s volume, which I use in preference to expected_label because a UUID cannot accidentally match the wrong drive.

Technical shape

It is Python with a mobile-friendly browser interface, drawn as a pedal-style control surface with labeled knobs rather than a plain file list, which is just a lot more fun to use because it is closer to what I am actually looking at when I reach for it. Optional I2C LCD support means it can drive a small physical display too, if one is attached, instead of relying on the browser alone. When usb.auto_eject_after_write is set, it unmounts and offers to power off the drive automatically once the verified write finishes, so I am not the one who forgets to eject it.

What I learned

Verification matters more than cleverness once a tool is touching hardware I can only have one of at a time. The SHA-256 read-back is the least glamorous line of code in the project and the one I actually trust. Building it as a small local web app rather than a script also turned out to matter, because a phone on the same network can reach it just as easily as a laptop can, and the pedal is not always sitting next to a keyboard.