RP2040 Controller options

[TomahawkLabs]

I'm looking for an RP2040 "stamp" style board, but hoping to find it within the dimensions of 18mmx55mm with as many (if not all of them) GPIO available. Trying to design my own RP2040 breakoutboard has proved to be rather difficult to self teach, and starting with only designing a daughterboard may be a more realistic first PCB design project.

[wjrii]

So it sounds like you've considered the 18x21mm stamp boards that have about 20 GPIO pins.  The only one I know of off the top of my head is the 21x21mm "dual bank" stamp boards that expose up to 30 GPIO.  Once you decide to go with the full 55mm length, there's usually little appetite to leave off the USB port.  I'd be interested as well to learn what's out there, though.

[fanf]

If you don’t need lots and lots of GPIO pins, the Waveshare RP2040-Tiny is a neat board with its own USB daughterboard. It’s 18x24mm. https://www.waveshare.com/rp2040-tiny.htm

[TomahawkLabs]

Ideally I would like a 6x21 matrix for easy routing and 2 pins for Data+ and Data- for the USB. Lastly I would like enough pins to keep the LED indicators for Caps, etc. I do think having all 30 would just make the project easier. I do not have a need for an integrated USB port on the RP2040 because I plan to use the RP2040 with a carrier board so the USB would only be useful in the initial stages of flashing the hex file, but even then, it could be done after it's soldered with the USB on the carrier board.

[TomahawkLabs]

I found by searching "RP2040 Module" I was able to find what I needed. I had found a writeup for a small RP2040 pcb design that indicated that RP2040 module = no integrated USB.

https://www.pcbway.com/project/shareproject/W157031ASS56_RP2040_712438f3.html

This is 15.2 x 52.1 mm which is darn near perfect. I think I may try to use this design and create a carrier board with this. The goal is to create a drop in PCB for the Apple M3501 (AEK 2). The reason for the PCB dimension limits was I plan to create a carrier board and place the RP2040 module where the original Toshiba 341-0731A IC is located. The plate already has the cutout in it to allow it to be mounted to the PCB.

This would allow it to be a drop in replacement into an original AEK 2 case. The plan is to also use the ADB ports and create a custom ADB > USB Type A. Visually this would create an OEM look, as the ADB connector has enough pins to support USB. Doing this would visually make the AEK 100% original, but with a heart transplant. One sub-goal would be to put RGB through hole LEDs in the carrier board for indicator lights. This would allow customization of the color of indicator light for those who may prefer blue/purple/etc over green.

[TomahawkLabs]

Further research shows that while the RP2040 is a fantastic chip, there are better off the shelf components that would help me materialize my goals. Specifically this off the shelf microcontroller. It just fits in the opening of the plate cutouts where the current MCU sits, has an integrated USB for programing off board/troubleshooting, it comes with native Bluetooth/battery and I don't have to solder any SMD components. The ESP32 also seems to offer more GPIO for future developments and features, like an SPI display or rotary encoder.

Using this off the shelf chip, I should be able to use Elmo's design as a reference to create a carrier board/PCB for the switches/LEDs to mount to. The only downside is there are 27 not 28 pins. This means I will have to remap the matrix to 6x20 vs 6x21 if I want enough pins for the LED indicators. But if this works out well it would be easy enough to create a new PCB that accommodates all the features I am looking for.