Raspberry Pi Pico W Booster Loader

This is an advanced second-stage bootloader for the Raspberry Pi Pico W and the SidecarTridge Multidevice board. The current 2.1.x series targets the RP2040-based Pico W and focuses on a web-based Manager, Atari ST terminal integration, OTA updates, and resilient offline-safe boot flows.

Key Features

• OTA (Over-The-Air) Updates
  The Booster app fetches and installs the latest apps or microfirmwares from a web server, making it easy to manage and update multiple solutions on a single device.

• Web-Based Manager
  Access and manage the device via a web browser. The interface simplifies app installation, updates, and system configuration without the need for additional software.

• Micro SD Card Support
  Store and manage files on a micro SD card, allowing apps to use external storage or turn the device into a file server.

• Catalog Filters in the Apps View
  Narrow the public app catalog dynamically with Platform and Features filters so it is easier to find the right microfirmware.

• Catalog Channel Selector
  Switch between the Stable and Beta catalogs from the Apps page with a single click. Pick Development or a fully custom URL from the Config page when you need it.

• Per-App Version Selector
  Pick which version of a microfirmware to install. The latest is selected by default, but when the publisher exposes prior versions in the catalog you can roll back or pin to a known-good build, with a confirmation step for downgrades.

• Offline-Capable Manager
  If Booster cannot connect to the configured WiFi network after its retry cycle, it stays usable in offline mode so already-downloaded microfirmwares can still be launched from the Atari ST terminal path.

• Atari ST Terminal Integration
  Use the Atari ST display as the main terminal, inspect connection details directly on screen, and launch installed apps from the keyboard when network features are unavailable or not needed.

• Network Diagnostics
  The Manager shows the current MAC address and WiFi signal strength on both the Atari ST display and the web UI, and it replies to ICMP ping requests when connected.

• Storage Workflows Through Microfirmwares
  Booster itself no longer exposes USB mass storage directly. Use dedicated storage-oriented microfirmwares such as File Manager or Multi-drive when you need file-transfer workflows.

• Multi-App Support
  Install and manage multiple app or microfirmwares simultaneously, ensuring flexible and dynamic usage.

• External Display Support
  Connect an external screen or run headless. Currently supports Atari ST high and low resolutions, with easy expansion to other display types.

• Global Settings
  Store system-wide configurations in flash memory, accessible via the web interface or terminal.

Booster components

The Booster app is designed to be modular and extendable. The key components include:

• Booster Core
  The heart of the system, responsible for managing the device, loading/unloading apps, handling the micro SD card, and providing the web interface.

• Placeholder App
  A temporary app that runs when no other app is installed. It hands control over to the Booster Core and is replaced when an active app is loaded.

• Global Settings
  Stored in flash memory, these settings apply to the entire device and its apps.

• Local Settings
  Each app has its own isolated configuration stored in flash memory, ensuring app-specific settings remain independent.

• Atari ST firmware
  The Booster app uses the Atari ST computer as the terminal for screen and keyboard input/output. A small custom firmware is included to handle the Atari ST's unique hardware and protocols.

Memory Map

The Pico W and Pico 2W feature a 2MB flash memory, structured as follows:

+-----------------------------------------------------+
|                                                     |
|              MICROFIRMWARE APP (1152K)              |  0x10000000
|          Active microfirmware flash space           |
|                                                     |
+-----------------------------------------------------+
|                                                     |
|                  BOOSTER CORE (768K)                |  0x10120000
|  - Manages device, apps, SD card, web interface     |
|  - Loads/unloads apps                               |
|                                                     |
+-----------------------------------------------------+
|                                                     |
|                  CONFIG FLASH (120K)                |  0x101E0000
|             Microfirmwares configurations           |
|                                                     |
+-----------------------------------------------------+
|                                                     |
|              GLOBAL LOOKUP TABLE (4K)               |  0x101FE000
|  Microfirmwares mapping to configuration sectors    |
|                                                     |
+-----------------------------------------------------+
|                                                     |
|              GLOBAL SETTINGS (4K)                   |  0x101FF000
|           Device-wide configurations                |
|                                                     |
+-----------------------------------------------------+

The Booster Core resides in flash memory from 0x10120000 (768K). This region is only modified when updating the core itself.

The Config Flash (120K at 0x101E0000) stores per-app settings, allowing up to 30 microfirmware apps, each allocated 4K of flash memory.

A Global Lookup Table (4K at 0x101FE000) maps microfirmware apps to their configuration sectors using unique UUIDs.

Finally, the Global Settings (4K at 0x101FF000) store system-wide configurations for the device and its microfirmware apps.

Each microfirmware app is loaded at 0x10000000 after powering on the device. It can be updated over the air or through the web interface.

This design ensures efficient memory usage while providing a structured and extensible platform for managing multiple apps and configurations on the Raspberry Pi Pico W.

Booster core libraries and components

External Libraries

These libraries are in different repositories and are included as submodules:

• Pico-SDK: The official Raspberry Pi Pico SDK, providing essential libraries and tools for development.
• Pico-Extras: A collection of additional libraries and utilities for the Pico platform, enhancing functionality and ease of use.
• no-OS-FatFS-SD-SDIO-SPI-RPi-Pico: A library for interfacing with micro SD cards using the SPI protocol, enabling file system access and management.

Internal Libraries

These libraries are part of the project and are included in the repository:

• cJSON: A lightweight JSON parsing library for C, used for handling JSON data in the web interface and configuration files.
• dhcpserver: A simple DHCP server implementation for the Pico, allowing the device to assign IP addresses to connected clients.
• dnserver: A DNS server implementation for the Pico, enabling hostname resolution for local network devices.
• httpc: A lightweight HTTP client library for making requests to web servers, used for fetching updates and resources.
• md5: A library for calculating MD5 hashes, used for verifying the integrity of downloaded files and updates.
• qrcodegen: A library for generating QR codes, allowing users to easily share device information and configurations.
• settings: The rp-settings library.
• u8g2: A graphics library for rendering text and images on various display types, used for the external display support in the Booster Core.

Building the Project

Initialize the submodules first:

git submodule init
git submodule update --init --recursive

Install the required dependencies:

• CMake
• Python 3
• GCC ARM embedded toolchain (arm-none-eabi-*)
• stcmd tooling for the embedded Atari ST terminal firmware

The root version.txt file defines the release string and is copied into the subprojects by the build scripts.

Common root builds:

./build.sh pico_w debug
./build.sh pico_w release
./build.sh pico_w minsizerel

The combined UF2 is written to dist/. If you pass any third argument, the root build also creates the full-image artifacts (*-full.uf2, upgrade.bin, and SIDECARTVERSION).

Downloading the Project

Firmware artifacts are published in the GitHub Releases section. If you build locally, use the files generated in dist/.

Installing the project

Go for the option that best suits you. Both options will install the bootloader on your Raspberry Pi Pico W.

###  Option 1: Using the drag-and-drop method

1. Connect the Raspberry Pi Pico W micro USB connector to your computer while holding the BOOTSEL button.
2. Your computer should recognize the device as the mass storage device RPI-RP2. Now you can release the BOOTSEL button.
3. Drag and drop a downloaded rp-booster-<version>-full.uf2 release asset, or a locally built dist/rp-booster-<version>-full.uf2, to the RPI-RP2 drive.
4. Wait for the file to be copied. When the copy is complete you can disconnect the Raspberry Pi Pico W from your computer.

### Option 2: Using picotool

With this method you must first install the picotool helper tool, which is a command-line utility for managing Raspberry Pi devices based on the RP2040 microcontroller.

1. Connect the Raspberry Pi Pico W micro USB connector to your computer while holding the BOOTSEL button.
2. Your computer should recognize the device as the mass storage device RPI-RP2. Now you can release the BOOTSEL button.
3. Flash the bootloader on your board:

picotool load -xv /path/to/rp-booster-<version>.uf2

Booster Quickstart Guide

Initial Factory Configuration for SidecarTridge Multidevice on Atari ST Series Computers

1. Format a microSD card with either exFAT or FAT32 file system and insert it into the SidecarTridge Multidevice board.

2. Plug the SidecarTridge Multidevice into the cartridge port of your Atari ST series computer.

3. Power on the Atari ST computer.

4. The Booster app will automatically start in Factory mode, showing the following message on screen:

   

   This screen confirms that the Booster app is running in Factory mode and is ready to be configured.
   Scan the QR code with your smartphone to connect to the WiFi network created by the Booster app, or manually connect via your WiFi settings.
   The default network details are:

   • SSID: SIDECART
   • Password: sidecart

5. Once connected to the WiFi, the Booster app will detect the connection and show the following screen:

   

   This screen invites you to open a web browser and navigate to either:

   • http://sidecart.local
   • or http://192.168.4.1 (if .local domains aren’t supported)

6. In your web browser, enter the URL shown above to access the web interface.
   You’ll be prompted to configure your home or office WiFi network.
   Select your WiFi SSID from the list (you can click Refresh if it doesn’t appear), then click it to continue.
   In this example, the network is CHISMEROUTER.

   

7. Enter your WiFi password and click the Connect button.

   

8. The Booster app will save the WiFi credentials to flash memory and reboot.
   It will then connect to your WiFi network and show this message:

   

   Meanwhile, the device will also display a reboot message on the Atari screen:

   

9. After rebooting, the Booster app will attempt to connect to your configured WiFi network:

   

10. Once connected successfully, the screen will show:

    

    Your WiFi setup is now complete. From now on, the Booster app will boot directly into Manager mode.
    See the next section for details on using Manager mode.

Booster Manager Mode

In Manager mode, the Booster app tries to connect to your configured WiFi network and then connects to the public repository of microfirmware apps.

If your DHCP network supports .local name resolution, you can access the web interface using http://sidecart.local. Otherwise, use the IP address assigned by your DHCP server and shown on the Atari ST screen.

If WiFi retries are exhausted, Booster falls back to an offline Manager mode. In that state network features are disabled, but the Atari ST terminal remains available so you can still boot already-downloaded microfirmwares manually.

The Atari ST Manager screen and the shared system information area in the web UI show the current MAC address and WiFi signal strength. When connected, Booster also answers ICMP ping requests to simplify network diagnostics.

Note: The device needs a SDHC or SDXC microSD card formatted with exFAT or FAT32 file system to work properly. The app will warn the user if the microSD card is not present or not formatted correctly.

Apps view

The Apps view shows:

• The list of installable apps from the public repository.
• The list of installed apps on the device.
• The list of apps that are not installed but are available on the microSD card.

This view is the default view when you access the web interface. At the top of the page a Catalog channel chip lets you switch between the Stable and Beta catalogs — clicking a channel saves the change and reloads the page. Below it, the Platform and Features filters let you narrow the catalog dynamically. While the catalog is being fetched, a loading indicator is shown.

Each app shows the following information:

• Name: The name of the app.
• Version: The version of the app.
• Description: A short description of the app.
• Features: A list of features supported by the app as a taxonomy.
• Computer: The computers supported by the app as a taxonomy.

If the catalog publishes more than one version of an app, a Version dropdown appears under the app name. The latest version is selected by default; older versions, when available, are listed in semantic-version order. The currently installed version is tagged "(current)" when it is not the latest.

At the right hand side of each app, you can see the following buttons:

• Install vX / Update to vX / Downgrade to vX: A single context-aware action button that installs the version selected in the dropdown. Its label and color reflect what the action will do relative to what is already installed. The button is hidden when the selected version is the one already installed. Downgrading to an older version requires an extra confirmation.
• Delete: Delete the app from the device microSD card. You can download the app again if you want to.

• Launch: Launch the app. This will install the app in the flash memory of the device and after reboot it will be launched automatically. If you want to launch an app that is already installed, you can use the Launch button at any time.

On Atari ST systems, Manager mode also supports terminal-driven manual boot: press ESC to enter the apps workflow, or press any SHIFT key to continue booting from GEMDOS.

When launching an app, the computer screen will show a message indicating that the app is being launched. The Booster app will make its best effort to also reboot the computer, but this may not always be possible. So assume that the computer is not rebooted and you need to do it manually.

The Booster microfirmware app is now installed in the flash memory of the device, and every time you power on the device, it will automatically launch the app.

To return to the Booster app, the user needs to use the command menu on the microfirmware app to do it, or press the SELECT button for more than 10 seconds and then power off and power on the device and the computer.

WiFi view

The WiFi view shows the list of available WiFi networks and permits some basic network configuration options:

• Country: The country code of the WiFi network. This is used to configure the WiFi module to use the correct channels and frequencies.
• Hostname: The hostname of the device. This is used to identify the device on the network. By default is sidecart.
• Wifi Power: The power of the WiFi module. From 0 to 4.
• Show RSSI: Show the RSSI of the WiFi module. This is used to show the signal strength of the WiFi network.
• DHCP Enabled: Enable or disable DHCP for the device. If disabled, the TCP/IP settings view lets you enter a static IPv4 address, netmask, gateway, and DNS servers.

The system information banner also shows the Pico W MAC address, which is useful when configuring router allow-lists or debugging network issues.

Don't forget to click the Save button to save the changes!

It's also possible to change the WiFi network. To do this, click on the new WiFi network from the list. A new window will open with the WiFi network details. Enter the password and click the Connect button.

The Booster app will save the WiFi credentials to flash memory and reboot. It will then connect to your WiFi network and show a message on the computer screen.

Note: If Booster cannot connect to the configured WiFi network, it stays in offline Manager mode. To restore the WiFi factory defaults and configure the network again, hold the SELECT button for more than ten seconds and then power-cycle the device and computer.

Device view

The Device view shows the device information and some basic configuration options:

• Apps folder: The folder where the apps are stored. By default is /apps. This folder is created on the microSD card when the Booster app is launched for the first time if it does not exist.
• Apps catalog URL: Pick the catalog channel — Stable, Beta, or Development — or choose Custom apps catalog URL to enter your own. The default is the Stable channel (http://atarist.sidecartridge.com/apps.json). The Stable and Beta channels are also reachable as a one-click chip on the Apps page.
• Boot feature: The UUID of the microfirmware app to load at boot time, or the Booster factory path. If the configured app cannot be found in flash memory, Booster falls back to Manager mode.
• SD card baud rate (KB): The baud rate of the SD card. By default is 12500. It can be safely increased to 25000. Above this value, the SD card may not work properly or the value will be ignored.

Don't forget to click the Save button to save the changes!

It also provides two buttons to reboot the device:

• Reboot the device: Reboot the device and load the microfirmware app in flash memory. This is the normal way to reboot the device.
• Restore to the default fabric settings: Reboot the device and load the Booster app in Factory mode. This is useful to reset the WiFi configuration or return the device to its default setup.

License

The source code of the project is licensed under the GNU General Public License v3.0. The full license is accessible in the LICENSE file.

The project can also be licensed under a commercial license. Please contact the author for more information.