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Anduril Flashlight Firmware + FSM Flashlight UI Toolkit

Anduril is a user interface for flashlights. It is written with FSM, a UI toolkit for flashlights.

What is FSM? The "SM" means "Spaghetti Monster", and the "F" can be any F word you like, such as "Flashlight" or whatever suits your mood. FSM also means "Finite State Machine", which is the type of abstraction used for defining user interfaces. It is like a flowchart turned into executable code.

Using Anduril

Anduril has many features, but the only things a person really needs to know to use it are:

  • Click for on/off
  • Hold to change brightness

For more in-depth use, read its user manual for full details.

If you want to know what changed recently, check the ChangeLog.

For info about hardware-specific features, like what the channel modes are on multi-channel lights, browse into the hw/ directories to find the hardware model and any hardware-specific documentation.

Flashing Firmware

Get the latest updates by flashing new firmware!

A few things are needed to flash firmware:

  • A firmware ".hex" file. Here's how to find the right .hex file.

  • A flashing adapter. The type of adapter depends on which MCU chip your light uses. It may be an UPDI 3-pin adapter (attiny1616 and newer) or an AVR ISP 6-pin adapter (attiny85, attiny1634).

    UPDI typically uses a "pogo pin" adapter, with spring-loaded pins to hold against copper pads on the driver circuit.

    AVR ISP typically has two parts -- a USB device (like a USBASP), and a physical adapter (like a pogo pin adapter or SOIC8 clip). SOIC8 is the least convenient, and is mostly only used on old models with attiny85 chips.

  • A firmware flashing program. A few compatible programs include avrdude, pymcuprog, and ZFlasher.

  • A computer or phone. Almost any modern computer or phone should be able to do it, as long as you can plug the adapter in and run a flashing program.

One particularly useful guide is at .

More info about installing flashing programs is below, in Flashing Programs.


The firmware can be deeply customized by modifying it and compiling your own versions, and this is encouraged.

To compile the firmware, it is strongly recommended that you use a Linux computer, ideally running Debian or Ubuntu (but almost any distro should work). Virtual machines work well, such as running WSL inside Windows. There is also a Docker container available (TODO: add link(s) here), if that is more convenient.


  • AVR toolchain packages:
    sudo apt install gcc-avr avr-libc binutils-avr

  • Other misc packages:
    sudo apt install git wget unzip bash

  • Atmel DFPs (Device Family Packs). A small script is included to download and install these for you:
    ./make dfp


Use the make script included in this repo. Run ./make --help for details about how to use it. In most cases though, you should be able to just run ./make by itself to compile all available build targets. Or give it a search term to limit builds to only a few, like ./make hank boost to build all firmwares for Hanklights with optional boost drivers.

The compiled firmware goes into the hex/ directory, ready to be used by any firmware flashing program.

Customizing Settings Per User

The build can be customized per user by placing overrides into the users/myname/ directory and letting the build script know your username. That way, your favorite settings can be applied automatically without having to modify the original source files.

Flashing Programs


Usually avrdude installs in a single command:

sudo apt install avrdude


If you use pymcuprog to flash firmware, a few extras are needed:

sudo apt install python3 python3-pip python3-venv
python3 -m venv .venv
source .venv/bin/activate
pip install pymcuprog

You'll need to source .venv/bin/activate every time you start a fresh shell, if you want to use pymcuprog. The activation lasts until the shell is closed or until you run deactivate.


If you'd like to help, there are several ways...

  • ToyKeeper has a Patreon site for donations, to help figuratively and literally keep the lights on.

  • Send pull requests or patches, to improve things directly. These can be code, documentation, tools, or anything you think is useful.

  • File bug reports for any problems you find.

  • Answer people's questions on public forums. If the same questions come up a lot, consider adding it to the documentation here.

  • Ask manufacturers to use this firmware, and to support its development.