Changelog

Table of contents
  1. Firmware Changelog
    1. 4.0.0 (2026-10-10) - Rescue and reliability release
      1. Changes
      2. New Features
      3. Fixes
    2. 3.1.0 (2026-02-01) - Maintenance release
      1. Changes
      2. New Features
      3. Fixes
    3. 3.0.0 (2025-06-01) - v3 release
      1. Changes
      2. New Features
    4. 2.1.0 (2024-11-21) - Commands release
      1. Changes
      2. New Features
      3. Fixes
    5. 2.0.0 (2024-10-15) - FAT12 and Upload release
  2. SWITCHER.TOS Changelog
    1. 4.0.0 (2026-10-09) - Settings and reliability release
      1. New Features
      2. Changes
      3. Fixes
    2. 3.1.0 (2026-02-01) - Shared code release
    3. 3.0.0 (2025-06-09) - v3 release
    4. 2.1.0 (2024-11-18) - Renaming images release
      1. Changes
      2. New Features
    5. 2.0.0 (2024-10-25) - Upload release
    6. 1.0.1 (2024-07-28) - First production release
  3. Rescue Switcher Changelog
    1. 4.0.0 (2026-10-10) - Self-test release
      1. New Features
      2. Fixes
    2. 3.1.0 (2026-03-11) - First release
  4. Hardware Changelog (ROM Emulator)
    1. 3.0.0 (2025-06-01) - v3 release
      1. Changes
      2. Fixes
    2. 1.1.0 (2024-06-01) - First production batch

Firmware Changelog

4.0.0 (2026-10-10) - Rescue and reliability release

This firmware release is for board revision 3 (RP2350). It works only with SWITCHER 4.0.0 and the rescue switcher 4.0.0, released with it: Upgrading to v4.0.0 explains how to move a board from firmware v3.x. Board revisions 1 and 2 stay on firmware v2.1.0.

Changes

  • The update file (sidecartridge-tos-rp2350a-v4.0.0.uf2) replaces the firmware only and keeps the drive, its TOS images and the settings. The full files (...-emutos-192k-full-..., ...-emutos-256k-full-...) install everything new, with EmuTOS 1.4 and the rescue switcher.
  • The board opens its ROMEMUL drive when a computer talks to it on the USB cable during its first 2 seconds, and now finds the computer through USB hubs too.
  • A REBOOT file now makes the board start serving TOS after the eject, with the USB cable still connected, instead of opening the drive again.
  • The board shows up on the computer as a USB drive only.
  • READ_BUS_TICKS values below 2 work as 2, and values above 19 as 19.
  • INFO.TXT has a Board variant line, which names the board the firmware is for.

New Features

  • RESCUE_TIMEOUT in CONFIG.TXT: start the rescue image without the RESCUE button, by switching the Atari on with its RESET button held.
  • ACCELERATED_BUS in CONFIG.TXT: the board always runs at its highest speed, for Atari computers with an accelerator board.
  • If the default TOS image cannot be served, the board starts the rescue image instead. With nothing to serve at all, it blinks the green LED and still opens its drive for the computer, so it can always be fixed.
  • The firmware refuses to run on a board it was not made for: the green and orange LEDs blink together.

Fixes

  • A board left without power for a few minutes could fail to start.
  • A volume with many TOS images copied from a Mac (about 29 or more) could corrupt the list of images.
  • A write to the drive that failed was reported to the computer as done; it is now reported as an error.
  • DEFAULT.TXT and RESCUE.TXT that were missing or could not be read are handled correctly.

3.1.0 (2026-02-01) - Maintenance release

This firmware release includes several maintenance improvements and bug fixes.

Changes

  • Improved writing performance with writing blocks protocol.
  • Better handling of USB disconnections during file transfers.
  • Lowered the speed of the access to the flash memory to improve stability to accomodate some flash memory chip series.
  • New unomunt procedure when the user ejects the ROMEMUL volume to avoid data corruption issues with some operating systems (Windows) that expect the device to wait for some time before actually unmounting the volume.
  • Power saving procedures improved to reduce power consumption when detecting the device is connected to the USB-C port.
  • Power off the VOL LED when the device ends unmounting and placed in low power mode.
  • EmuTOS 1.4 is now the default TOS image in the device.

New Features

  • SWITCHER.TOS app now shares the same codebase with the Amiga version, improving maintainability and adding support for future features.

Fixes

  • Fixed an issue where the FAT12 filesystem could become corrupted when uploading images on a fragmented drive.
  • Fixed an issue in the sector count calculation where the RP2350 microcontroller could misbehave rounding numbers, leading to corrupted FAT12 filesystems in some cases.

3.0.0 (2025-06-01) - v3 release

This firmware release is the first stable release of the SidecarTridge TOS v3 board. It includes several new features and improvements over the previous versions.

Changes

  • The firmware is now based on the RP2350 microcontroller, which provides more features and better performance.
  • The firmware now supports 512KB ROMs.
  • The upload feature now display the progress in blocks of 64KB, which is more efficient and faster.

New Features

  • The firmware now supports the RP2350 microcontroller, which provides more features and better performance.
  • There is a new red LED indicator that lights up when the board is powered on.
  • There is a new green LED indicator that lights up when the firmware is running.
  • There is a new orange LED indicator that lights up when the internal USB drive is mounted or transferring data.
  • There is a new CONFIG.TXT file that allows the user to configure some advanced firmware options.
  • The parameter READ_BUS_TICKS in the CONFIG.TXT file allows the user to configure the number of ticks to wait for the bus to be ready before reading it. This is useful for some Atari ST motherboards that require more time to read the bus. Each tick is 12.5ns.
  • The parameter USE_OE in the CONFIG.TXT file allows the user to configure if the OE signal is used or not. Not strictly necessary for Atari computers.
  • Support for Commodore Amiga on EmuTOS.

2.1.0 (2024-11-21) - Commands release

This firmware release adds some maintenance commands and modifies the creation of the INFO.TXT file to avoid issues when powering on the device.

Changes

  • When plugged to the USB port in mass storage mode when the user eject the ROMEMUL volume it does not automount again automatically. The user must press RESET button or unplug and plug again the USB connector.

New Features

  • The commands feature of the version 1.x is back. Now, if a user creates a folder or file with the following names, it will trigger an action in the device when ejected:

  • REBOOT: When the volume is ejected, the device will try to mount again the volume again.
  • RESET: When the volume is ejected, the device will enter in BOOTSEL mode. The volume RPI-RP2 will be mounted again and the user can flash a new firmware.

The files or folders will be deleted after the action is triggered.

Fixes

  • The creation of the INFO.TXT file was modified to avoid issues when powering on the device. Now, when powering on the device there is not any write operation in the mass storage device until the user decides to do it. This avoids issues with some users pressing repeatedly the RESET button when powering on the device and not completing the boot process.

2.0.0 (2024-10-15) - FAT12 and Upload release

This firmware release adds support for FAT12 filesystems and the ability to upload images to the Sidecartridge ROM Emulator from the SWITCHER.TOS app.

### 1.0.4 (2024-06-01) - First production release

First production release of the Sidecartridge ROM Emulator.

SWITCHER.TOS Changelog

4.0.0 (2026-10-09) - Settings and reliability release

For firmware v4.0.0 only: SWITCHER 3.x does not work with firmware v4.0.0, and 4.0.0 does not work with an older firmware.

New Features

  • C shows the board’s settings, read from CONFIG.TXT, and the SWITCHER’s version.
  • When the SWITCHER and the firmware do not match, the message shows both versions and says to install the SWITCHER released with the firmware.
  • Images of 1,000 KB and more show their size in MB.

Changes

  • An image that fails the check after an upload is removed from the drive, and an upload that fails part-way leaves nothing behind.
  • ESC cancels the rename prompt.

Fixes

  • Every return to the list lost some memory, so long sessions on a 512 KB machine ran out and crashed.
  • A drive with many images copied from a Mac could corrupt the list.
  • When the free space could not be read, any upload was let through; it now shows 0 KB and refuses it.
  • Images of 1 MB showed as 256 KB.

3.1.0 (2026-02-01) - Shared code release

For firmware 3.1.0. The Atari SWITCHER now shares its code with the Amiga version.

3.0.0 (2025-06-09) - v3 release

For firmware 3.0.0.

  • Uploads are copied in blocks, with a progress bar.
  • The title names the computer.

2.1.0 (2024-11-18) - Renaming images release

This release adds a feature to rename the images. Now the user can rename the images to a custom name and the SWITCHER.TOS will show the custom name in the menu.

Changes

  • To delete a file, the user has to confirm the deletion by accepting with an uppercase Y or rejecting with any other key.

New Features

  • The user can rename the images to a custom Long File Name (LFN) of up to 63 characters.

2.0.0 (2024-10-25) - Upload release

This release adds support for FAT12 filesystems and the ability to upload images to the Sidecartridge ROM Emulator from the SWITCHER.TOS app.

1.0.1 (2024-07-28) - First production release

First release of the SWITCHER.TOS app: it lists the TOS images in the board and selects the one that boots.

Rescue Switcher Changelog

The rescue switcher is the rescue image the board starts when you hold the RESCUE button. See ROM Rescue Switcher.

4.0.0 (2026-10-10) - Self-test release

For firmware v4.0.0 only: the rescue switcher 3.1.0 stops at its “not compatible” screen under firmware v4.0.0.

New Features

  • T runs a self-test of the board. It checks every address and data line, thousands of random reads, that the board answers commands (8, then 1,000), that its flash reads back the same every time, and the ROM list and settings stored in it; it names the machine, the monitor line and the RAM.
  • S on the self-test screen runs a 30-second soak test.
  • At start it checks that the board answers, and says so at once if it does not.
  • The start screen shows the version and the image size.

Fixes

  • On a monochrome monitor the screen could come up shifted after a cold start.
  • Long messages and names no longer run into the next line.

3.1.0 (2026-03-11) - First release

The first rescue switcher, for the Atari ST, STE and Amiga 500 and 2000, with firmware 3.1.0.

Hardware Changelog (ROM Emulator)

3.0.0 (2025-06-01) - v3 release

This hardware release is the first stable release of the SidecarTridge ROM Emulator v3 board with the RP2350 microcontroller. It includes several new features and improvements over the previous versions:

  • The board is now based on the RP2350 microcontroller, which provides more features and better performance.
  • The board now supports 512KB ROMs.
  • The board includes three LED indicators: a red LED that lights up when the board is powered on, a green LED that lights up when the firmware is running, and an orange LED that lights up when the internal USB drive is mounted or transferring data.
  • Support for the firmware v3.0.0 and later.

### 1.1.1 (2024-10-01) - Minor changes

Changes

  • Larger pads for the RESET and BOOTSEL buttons.

Fixes

  • Swap the UART pins to match the Raspberry Pi Pico pinout.

1.1.0 (2024-06-01) - First production batch

First production batch of the Sidecartridge ROM Emulator.

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