SidecarTridge Multi-device ROM Emulator

Source code CHANGELOG Report BUG v2.2.0

SidecarTridge Multi-device ROM Emulator icon

This is a microfirmware application for the SidecarTridge Multi-device that emulates the cartridge ROM of an Atari ST, STE, Mega ST, Mega STE or Falcon computer: pick a ROM image from the microSD card or download one from the internet catalog, and the computer runs it as if a physical cartridge were plugged in.

See the ROM Emulator in action:

A list of available ROM files can be found in the ROMs repository. ROMs can be downloaded directly from the setup screen with the D key. In headless autorun mode, copy the ROM files to the microSD card from your computer.

Want to turn your own Atari ST program into a cartridge ROM? Use the SidecarTridge USM web app to pack any .PRG or .TOS file into a 128 KB .ROM image in your browser. See Making a cartridge from your own programs below.

Table of contents
  1. 🚀 Installation
  2. 🕹️ Usage
    1. ⚙️ Setup Screen Keys
    2. 💾 Browsing the ROMs on the microSD Card
    3. ⬇️ Downloading ROMs from the Catalog
    4. 🛠️ Settings
    5. 🚀 Launching a ROM
    6. 🔘 The SELECT Button
    7. ❌ Delay/Ripper Mode
    8. ▶️ Headless Autorun Mode
    9. 🧩 Things the App Handles by Itself
  3. 🧰 Making a Cartridge from Your Own Programs: USM Web
  4. 🛠️ Setting Up the Development Environment
  5. 📄 License
  6. 🤝 Contributing

🚀 Installation

To install the ROM Emulator app on your SidecarTridge Multi-device:

  1. Launch the Booster App on your SidecarTridge Multi-device.
  2. Open the Booster web interface.
  3. In the Apps tab, select “ROM Emulator” from the list of available apps.
  4. Click “Download” to install the app to your SidecarTridge’s microSD card.
  5. Once installed, select the app and click “Launch” to activate it.

After launching, the app runs every time your Atari computer is powered on. An update installed from Booster keeps your settings, your selected ROM and its mode.

🕹️ Usage

When no ROM has been launched, the computer shows the setup screen. When one has, the computer runs it at every power-on and reset, until you press SELECT on the Multi-device (see The SELECT button).

On first use, the app creates the default ROM folder, /roms, on the microSD card if it does not exist yet.

The setup screen

The bar at the top shows the microSD card’s and the Wi-Fi’s icons. Each section shows its state: the selected ROM and the Delay/Ripper mode, the card, the network and the last download. A message, such as a ROM just selected, shows for a few seconds on a dark band above the prompt. The setup screen comes up at once: the network and the catalog refresh happen behind it.

⚙️ Setup Screen Keys

Each option is a single key, with no RETURN:

KeyDescription
BBrowse the ROM files on the microSD card.
DDownload a ROM file from the internet catalog.
LLaunch the selected ROM.
RTurn the Delay/Ripper mode on or off.
SSettings: change the app’s settings with typed commands.
EExit to the desktop without loading a ROM.
XReturn to the Booster menu.
MDraw the menu again.

Starting with v2.2.0, browsing and launching are two separate steps: B selects a ROM and L loads it. Before, choosing a ROM in the list launched it at once. Also, the SHIFT keys no longer boot the desktop from the setup screen, so capitals can be typed in the settings: use E instead.

💾 Browsing the ROMs on the microSD Card

B lists the ROM files in the ROM folder (/roms by default; the FOLDER setting). Files ending in .img, .rom, .stc or .bin are listed; a ROM can be up to 128 KB (.stc images carry 4 more bytes at the start).

The ROMs on the microSD card

Move with the cursor keys: UP and DOWN through the list, LEFT and RIGHT a page at a time. RETURN shows the ROM’s details:

A ROM's details

RETURN again selects it, and the setup screen comes back with it as the ROM to launch. ESC goes back.

⬇️ Downloading ROMs from the Catalog

D lists the ROMs in the internet catalog. The app keeps a copy of the catalog on the microSD card and refreshes it in the background whenever the network comes up, so the list is there even when the network is not (the screen says so). The catalog can have any number of entries.

The ROM catalog

RETURN on a ROM shows its details:

A catalog entry's details

RETURN again downloads it to the ROM folder, with its progress on the screen. ESC goes back to the setup screen while the download goes on, its progress shown in the Catalog section.

A download in progress

When it is complete, the ROM is selected, ready to launch:

After a download

A ROM whose name has spaces is saved with them (for example Buggy Boy.img). A download whose size does not match the catalog is deleted instead of selected.

The catalog and the ROMs come over HTTPS, from https://roms.sidecartridge.com/roms.csv by default. To use a catalog of your own, set its URL in the HTTPS_CATALOG setting; it can be https:// or http://, and its ROMs are fetched from the same server. The connection is encrypted, but the server’s certificate is not verified. Wi-Fi is set up in Booster; if the network drops, or was not there at boot, the app joins it again by itself.

🛠️ Settings

S opens the settings, which take typed commands, each ended with RETURN: print lists them, get KEY shows one, put_str KEY VALUE changes a text setting (put_int and put_bool the others), and save keeps the changes. m and RETURN, or ESC, go back to the setup screen.

The settings

SettingMeaning
FOLDERThe ROM folder on the microSD card.
HTTPS_CATALOGThe catalog’s URL.
EMULATEDThe selected ROM.
MODE255 for the setup screen; 0 runs the ROM, 1 waits for SELECT first (Delay/Ripper).

🚀 Launching a ROM

L writes the selected ROM to the Multi-device’s flash memory, with its progress on the screen, reads it back, and resets the computer into it. The computer then behaves as if the ROM were on a physical cartridge, at every reset and power-on. A ROM that cannot be launched (missing, empty, larger than 128 KB) is refused with the reason before anything is changed, and the previous one stays.

After E exits to the desktop, resetting the computer brings the setup screen back.

🔘 The SELECT Button

  • A short press while a ROM runs brings the setup screen back: press it, then reset the computer.
  • In Delay/Ripper mode, the first press starts the ROM (see below).
  • Holding it for 10 seconds is a factory reset: the Multi-device’s settings are erased and it starts Booster.

The button is answered during long operations too, such as a download, a launch or the network’s start.

❌ Delay/Ripper Mode

The Delay/Ripper mode loads the ROM only when you press the SELECT button on your Multi-device: the computer boots without the cartridge until then. To turn it on or off, press R in the setup screen before launching.

The Ripper mode was useful combined with tools like Ultimate Ripper. To use it, follow these steps:

  1. Download the Ultimate Ripper ROM file from the catalog (D).
  2. Turn the Ripper mode on in the setup screen (R).
  3. Launch the Ultimate Ripper ROM file (L).
  4. Now reset or power cycle your Atari computer and load your own application or game.
  5. When you want to rip the ROM, press the SELECT button on your Multi-device. The game or application should continue running.
  6. Reset (not power cycle) your Atari computer. The screen will look like it is frozen. Now you can press F1 (move memory to allocate the ripper program) or F2 (use memory available to allocate the ripper program) to enter the Ultimate Ripper menu.

Ultimate Ripper does not work in high resolution, nor on a Falcon.

▶️ Headless Autorun Mode

For a computer whose keyboard or screen does not work (a diagnostic cartridge, for example), the app can launch a ROM without showing the setup screen.

  1. Create a text file named .autorun in the ROM folder of the microSD card (/roms by default). Create the folder if it does not exist yet.

  2. Write on its first line the name of a ROM in that folder, for example:

    diagnostic.img
  3. Save the file, safely eject the microSD card from your computer and insert it into the Multi-device. If the device has not been configured before, follow Auto setup and headless factory configuration first.

At the next start the app launches that ROM without the setup screen, and the Multi-device’s LED blinks. A SELECT press then restarts into the ROM. Delete or empty .autorun to stop it.

🧩 Things the App Handles by Itself

  • The microSD card can be taken out and put back while the setup screen is up: the card is found again by itself.
  • The network: if the Wi-Fi drops or was not there at boot, the app joins it again by itself.
  • After an unexpected restart of the Multi-device, the setup screen says why (“Last restart: …”) for a few seconds. The Multi-device restarts by itself if it ever hangs.

🧰 Making a Cartridge from Your Own Programs: USM Web

USM Web packs one or more Atari ST .PRG or .TOS programs into a 128 KB cartridge ROM image that this app can launch. It runs in a recent Chrome, Firefox or Safari, and your files never leave your computer: the image is built in the browser. The same image also works in Hatari and STEem.

USM Web

  1. Add programs: drag and drop one or more .PRG or .TOS files onto the box, or click browse. Each must be an Atari ST program of up to 128 KB that does not load other files when it runs (the cartridge has no folders or files of its own). They appear on the cartridge’s C: drive in the list’s order. For each one you can choose:
    • Compress (-z): packs the program; it is kept as it is when packing would not make it smaller.
    • Init flag (-f): whether TOS runs the program by itself after a reset. None leaves it on the C: drive to open from the desktop; 3 runs it before the boot disk, the usual choice for a launcher.
  2. Cart options:
    • Output format: .ROM, the standard cartridge image; .STC, STEem’s (with 4 more bytes at the start; this app takes it too); or a diagnostic cartridge (Classic mode, one program), which TOS runs right after a reset.
    • Mode: Default copies each program into RAM and runs it there, and works with any program; Classic (-c) runs it straight from the cartridge, only for programs written for that.
  3. Build: click Build cart. The log shows each program’s result.
  4. Download: give the file a name and click Download. Build another starts again.

Copy the image to the ROM folder on the microSD card (/roms by default), then select it with B and launch it with L. The ? buttons on the page explain every option.

🛠️ Setting Up the Development Environment

This project is built on the SidecarTridge Multi-device Microfirmware App Template.
To set up your development environment, please follow the instructions provided in the official documentation.

📄 License

This project is licensed under the GNU General Public License v3.0.
See the LICENSE file for full terms.

🤝 Contributing

Made with ❤️ by SidecarTridge

Previous: Microfirmwares Main Next: RTC Emulator