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jvanderberg
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Joined: 06/05/2026
Location: United States
Posts: 22

Posted: 06:22pm 18 May 2026

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This is no-compromises RP2350B dev board that breaks out all 48 GPIOs. It's inspired by the Pimoroni Pico LiPo 2 XL W, which still supports the original 40 pin layout of the 'classic' Pi Pico boards. I think the pimoroni board does way too much, and I am not sure why it has castellated edges, because it's got chips on both sides, it can't be soldered down.

My goals for this version:

- 16MB Flash / 8MB PSRAM (CS GP0)
- Expose all 48 GPIOs with castellated edges (a common nit with previous versions)
- Support the original Pi Pico footprint for the first 20 pins on either side
- USB-C / Radio Module 2
- Everything on the top side so it's solderable (there are solder jumpers on the back side)
- Try to keep trace routing sane with not too many vias.

I haven't sent this version to production yet, and am looking for feedback. I have made PCBs based based on the same schematic but with a different PCB layout, and it all works. I have one in my PicoCalc right now.

You can find the kicad files here: https://github.com/jvanderberg/pico-stretch2. It's a 4 layer board with Inner1/Inner2 as ground planes. This helps with signal integrity and EMI for the traces that do have to move from the front to the backside.

Definitely would appreciate feedback before I send this off to production.

javavi

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Joined: 01/10/2023
Location: Ukraine
Posts: 555

Posted: 06:49pm 18 May 2026

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Please make the PSRAM CS signal configurable via solder jumpers, at least between GP0 and GP47.

And route the USB signals to the contact pads on the underside of the board near the connector.
Edited 2026-05-19 04:54 by javavi

jvanderberg
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Joined: 06/05/2026
Location: United States
Posts: 22

Posted: 06:55pm 18 May 2026

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javavi said Please make the PSRAM CS signal configurable via solder jumpers, at least between GP0 and GP47.

And route the USB signals to the contact pads on the underside of the board near the connector.

I'll think about the first, it might be pretty hard given the layout, but there's still a lot of freedom once you get to the backside.

The USB pads are a good idea, I think that should be easy.

javavi

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Joined: 01/10/2023
Location: Ukraine
Posts: 555

Posted: 07:20pm 18 May 2026

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I wasn’t able to view the schematic; if possible, please export it in an accessible format.
Preferably, the radio module should not use any of the ports of the original Pico module.

Pay attention to the quality of the components in the chip’s power circuitry.
With proper core power, the RP2350 chip is capable of operating at 504 MHz.
Edited 2026-05-19 05:34 by javavi

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