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Forum Index : Microcontroller and PC projects : PicoMite RP2350B DIL Development board, 16Mb flash + 8 MB PSRAM
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| matherp Guru  Joined: 11/12/2012 Location: United KingdomPosts: 10379 |
Slightly modified layout based on constructive (blunt) criticism on the Raspberry Pi forum. Probably makes no functional difference but definitely better. Gerber_PCB1_2025-06-27.zip BOM_Board1_PCB1_2025-06-27.zip  |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 1504 |
Is there a prize for guessing? I ain't gonna win  |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10379 |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 1504 |
I cut the ground off also but as Mick pointed-out, the circuit continuity-test in SL6 made it obvious. Such a great layout tool.  |
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| scruss Regular Member  Joined: 20/09/2021 Location: CanadaPosts: 94 |
Sorry about that. I thought twice about using the term "overclocking" when I posted the link, as certain users over on the RaspberryPi site have a fundamentalist approach to that word. |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10379 |
No problem, the layout comments were valid but for overclocking they haven't explored the issues when you need to write to flash and whatever they believe my board overclocks better in an MMBasic environment than the Pimoroni. |
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| Bleep Guru Joined: 09/01/2022 Location: United KingdomPosts: 660 |
The guy making the comments isn't a Pi engineer, probably just someone who likes telling everyone how bad everyone else's designs are! If you're happy to make the changes and they seem reasonable, then just ignore the bluntness :-) some people are like that. |
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javavi Guru Joined: 01/10/2023 Location: UkrainePosts: 510 |
@matherp Overall I like your design of the RP2350B DIL 64 module I don't quite understand why the choice fell on the GP0 pin for the CS PSRAM signal? For the RP2350B chip, it would be more logical to use the last port GP47, or to provide the ability to select using soldered jumpers. |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10379 |
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| javavi Guru Joined: 01/10/2023 Location: UkrainePosts: 510 |
@matherp Still, I think that it would be possible to bring out the GP0 port to pin 3, for those who are not going to use the PSRAM on the module. |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10379 |
My choice. If you want to do that then here is the current easyeda design file Pico2350DILV1.2.zip |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8048 |
I completely support GP0 for PSRAM select. It's actually the only logical choice in MMBasic. Only four alternative pins are possible: GP0, GP8, GP19 and GP47. GP8 is the default MMBasic pin for COM2, used for PS2 keyboards and the console port on HDMI systems. Yes you can change it, but it can be awkward in some cases. GP19 is one of the HSTX pins so cannot be used on HDMI systems. GP47 is one of the eight ADC input pins. If you use that then *someone* will want all eight... GP0 has no default function in MMBasic. Why complain about GP0 not being available when there is a complete 16-bit port no longer interrupted by ADC pins from GP20 upwards? :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 1504 |
My in-depth review: It's perfect |
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| tabemann Newbie  Joined: 21/07/2025 Location: United StatesPosts: 6 |
The main problem I foresee here is software, e.g. zeptoforth, that expects GPIO0 to be UART0 TX (e.g. for the serial console). As a result this would require custom firmware to be built just for this board in particular, which seems unreasonable to me. |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4068 |
It can't be (or at least shouldn't be) much effort to #define the console (& any other hardware)! They ought to be #define'd anyway... Or, better, auto-detect at runtime the board the software is on. John |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8048 |
You are battling the accepted use of pins on the PicoMite - and the fact that there is only a choice of 4 possible PSRAM enable pins. :) Two more are lost to the HSTX (needed for HDMI) and the MMBasic default serial port. GP0 is the only one that is free really. The PicoMite now has definable pins for the console, the default being GP8 and GP9. This is historic, going back to the early Micromite, so it gives a degree of software compatibility across all the MMBasic platforms. Some of the older ones, such as the Micromite, don't have mappable IO so you are stuck with what the hardware gives you. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 1504 |
I for one, would like to have the hi-res version of this   Edited 2025-07-22 04:33 by PhenixRising |
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| tabemann Newbie Joined: 21/07/2025 Location: United StatesPosts: 6 |
The console definitely could be selectable at build time, but that would still mean that I would have to put together builds just for this one board, or that I would expect anyone who wanted to use this board to install the arm-none-eabi toolchain and build from scratch for it. As for auto-detecting at runtime, how would one go about detecting this particular board vis-a-vis a different RP2350B board such as the Pimoroni Pico Plus 2? |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8048 |
Well, the Pimorini Pico Plus 2 is odd anyway as it uses the RP2350B but squeezes it into a 40-pin module and doesn't connect a lot of the GPIO pins. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| tabemann Newbie Joined: 21/07/2025 Location: United StatesPosts: 6 |
The main value of the Pimoroni Pico Plus 2 is that it is pin-compatible with the Pico 2 yet at the same time you get 16 MiB of flash and 8 MiB of PSRAM. Same with the Pico Plus 2W and the Pico 2W. (They do have a connector to break out a number of other GPIO's but I've never used it myself.) |
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