The RP2040 microcontroller has found its way into a potentially new form factor. Timonsku created a proof-of-concept RP2040 M.2 Add-On Card that's compliant with M.2 B-Key and has access to the USB signals.
"This is mostly a demonstration that it is easy to make your own M.2 compliant addon cards."
The board contains a sample of the RP2040 microcontroller, a WS2812 (NeoPixel), a Qwiic connector, and broken-out GPIO pins. The most prominent feature is its form factor. It has an edge connector and is size-compliant for an M.2 B-Key.
M.2 is well-known in the PC world for SSDs. On the connector are pins for high-speed busses like PCI-Express 4.0, Serial-ATA 3.0, and USB 3.0. However, not all M.2 cards or sockets support all three interfaces. Timonsku picked the M.2 B-Key because it is very likely to include USB signals.
Your desktop or laptop likely has one of these sockets. So you might ask the same question that @PoweredByWill did on Twitter: can you install an RP2040 inside of your computer?
Timonsku points out there are two issues. First, the M.2 socket may not have the RP2040's required USB signals. (The M.2 specification does not require them to be present.) And second, it is tough to automate re-programming the RP2040 while it is inside of a computer. You would need GPIO-level access to enable the boot and reset signals. Usually, you would assert them using the on-board pushbuttons. However, there could be other solutions to this limitation.
We recently wrote about the Piunora. It is a carrier that puts a Raspberry Pi 4 Compute Module (CM) into an Arduino Uno form factor. Timonsku jokes that you can combine the tiny RP2040 with its larger cousin, the Pi 4, using the Piunora's M.2 socket!
At the time of this writing, the Piunora Crowd Supply campaign is now active!
Currently, this board is a proof-of-concept. Timonsku plans to open-source the design so that if you'd like to consider incorporating the form factor into your project, you can. Those interested in seeing the RP2040 M.2 become a product, ping Timonsku on this Twitter thread.