Build a microfirmware for the Atari ST.
Eleven steps, in order, from an empty machine to a microfirmware listed in this store. Each step assumes you did the one before it. Nothing assumes you have written 68000 assembly, used the Raspberry Pi Pico SDK, or seen this hardware before.
What you end up with
A .uf2 file you can flash to the board, carrying an app that shows up in
Booster's app list on your own device, next to the apps in the
published catalogue . If you want, it also ends in
a pull request that adds it to the public catalogue everyone else browses on this site.
The microcontroller half of a microfirmware emulates the Atari's cartridge bus in real time. That cannot be simulated on a PC, so there is no way to complete this track without a SidecarTridge Multi-device and a Raspberry Pi Pico W . Step 2 lists everything.
The eleven steps
Steps 1 to 6 get the template building and running unchanged. Steps 7 to 9 are where it becomes your microfirmware, and 10 and 11 put it in front of other people. If you are impatient, you still cannot skip 3 and 4 because everything else depends on them.
If you have a .uf2 with a real UUID and an apps.json you
host, none of the setup applies to you. Go straight to the part that gets your app
into the public catalogue.
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What a microfirmware is
The two halves of your app, where each one runs, and how Booster loads it.
-
What you need
The hardware and software checklist. Work through it before installing anything.
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Set up the toolchain
The Pico SDK, the Atari cross-compiler in Docker, VS Code, and the environment variables that tie them together.
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Install Booster
The bootloader that has to be on the board before any microfirmware can run.
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Pick a template
Two starting points: a command-driven app, or a full-screen framebuffer app.
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Your first build
Compile it, flash it, and watch the unmodified template run on real hardware.
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How the code is laid out
The two source trees, the shared memory map, and the limits you must not break.
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Build your idea with Claude Code
What to tell an AI assistant so the code it writes actually fits this hardware.
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Test and debug
Serial output, the debug probe, and what to try when the screen stays black.
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Publish to the store
A real UUID, a release build, your app's descriptor, and somewhere to host it.
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Get listed in the store
The one pull request that adds your origin to the catalogue every device downloads.
Keep the reference docs open too
This track is the walked path. It tells you what to type and why, in order. It does not replace the SidecarTridge documentation, which goes far deeper into how the board and the Atari actually work. These are the pages worth having in another tab.
- Introduction , the shortest description of what the Multi-device is and does.
- Getting started , flashing the firmware, Wi-Fi setup and the web interface.
- User guide and Parameters , for living with the device once it works.
- Programming guide , the full development environment and project structure.
- Microfirmwares , what they are and how users install them.
- Architecture and design , covering memory, flash and bus contention, the constraints behind the rules you will follow.
- Hardware interface , pinouts and timing and the PIO state machine, if you want to know how the illusion works.
- Compatibility , Troubleshooting and the FAQ , for when the hardware rather than your code is the problem.
For the hardware itself, Raspberry Pi document the Pico-series boards , the C/C++ SDK you will build against, and the Debug Probe you will want by step 9.
About the commands in this guide
Every command, path, environment variable and constant on these pages was copied from an upstream source, not invented here. The reference documentation and the template repositories are the authority; if they disagree with this guide, believe them and please open an issue so the guide gets fixed.
That release moved the apps catalogue to this site, renamed the channel options on the Config page, and added a deploy API that pushes a build over Wi-Fi. Steps 4, 6 and 10 assume it. On an older Booster the flashing and publishing instructions still work, but the Wi-Fi deploy does not exist and the catalogue lives elsewhere.
Checked against docs.sidecartridge.com,
md-microfirmware-template, md-framebuffer-template and
rp2-booster-bootloader on 2 August 2026.