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Forum Index : Microcontroller and PC projects : Warning to board designers - do not use VGA or I2S on pins>GP31

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matherp
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Joined: 11/12/2012
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Posted: 07:48pm 18 Mar 2025

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As per the title

absolute no-nos pins<GP16 + pins>GP31

So OPTION VGA PINS GP0, GP32 is impossible and can never be made to work nor can
OPTION AUDIO I2S GP0, GP32

OPTION VGA PINS GPna,GNnb where both are >= GP32 doesn't work and is unlikely ever to work

OPTION AUDIO I2S GPna, GPnb where both are >= GP32 doesn't work and based on current testing may not ever work without a major re-write which isn't going to happen.

homa

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Joined: 05/11/2021
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Posted: 10:46pm 18 Mar 2025

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Thanks for this important information.

I have also often wondered which peripherals are best connected to which GPIOs. This information should at least be added as a footnote to the graphical representation in the manual starting on page 11 in the Hardware Details section!

Matthias

Amnesie
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Joined: 30/06/2020
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Posted: 11:02pm 18 Mar 2025

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homa said
I have also often wondered which peripherals are best connected to which GPIOs. This information should at least be added as a footnote to the graphical representation in the manual starting on page 11 in the Hardware Details section!
Matthias

Same here! This is the reason I am sticking as much as possible to the original design... But often there is not standard. With my current designed PCB I am using GP27 and GP28 for the PS/2 mouse... Which results in a total useless GP26 since it is ALWAYS at 3,3V... Maybe this is a bug or a Raspberry Pi internal "ADC thing"...

Anyways, it is good that Peter warns about possible issues :)

Greetings
Daniel

Volhout
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Joined: 05/03/2018
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Posted: 07:41am 19 Mar 2025

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All,

Should be clear that this only applies to the RP2350B.
The RP2350A and RP2040 do not have GP numbers 32 and above.

Volhout
Edited 2025-03-19 17:41 by Volhout

PicomiteVGA PETSCII ROBOTS

matherp
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Posted: 08:11am 19 Mar 2025

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Quote Same here! This is the reason I am sticking as much as possible to the original design... But often there is not standard. With my current designed PCB I am using GP27 and GP28 for the PS/2 mouse... Which results in a total useless GP26 since it is ALWAYS at 3,3V... Maybe this is a bug or a Raspberry Pi internal "ADC thing"...

Sounds like a H/W fault at your end. Definitely not the case with a bare Pico2 running PicoMiteVGA V6.00.02RC5 . Tested with the pin as a digital output, digital input and analog input

WhiteWizzard
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Joined: 05/04/2013
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Posted: 01:11pm 19 Mar 2025

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@Peter,

I understand the title, and also the examples given in your first post, but the following also implies no pins below GP16 too.

matherp said …..
absolute no-nos pins<GP16 + pins>GP31
…...

Is this correct?

matherp
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Posted: 02:17pm 19 Mar 2025

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Quote but the following also implies no pins below GP16 too.

No of course not.

Quote So OPTION VGA PINS GP0, GP32 is impossible and can never be made to work nor can
OPTION AUDIO I2S GP0, GP32

Sasquatch

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Joined: 08/05/2020
Location: United States
Posts: 377

Posted: 02:34pm 19 Mar 2025

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Hi Peter,

Thank you for the updated info regarding GPIO 32-47 and Thank You for all your hard work bringing the PicoMite to this community!

I think the functionality of GPIO Pins 0-31 under MMBASIC are well documented. as you point out in this thread GP32-47 may not be suitable for all functions. I am aware that some GPIO functions are implemented in the RP2350 hardware while others are "bit-bashed" in software, however, how these functions may or may not be appropriate for GP32-47 is not clear.

In your "spare time" (LOL) could you please document which of the following functions should currently be expected to work on GPIO 32-47 (pending further testing/debugging) under MMBASIC on the RP2350B devices? This will be important information to add to the PicoMite Manual!

Thanks Again!

VGA NO
HDMI NO
I2C NO
PIO NO?

Uart(COMn:) ???
SPI ???
SD CARD ???
ADC(GP32-39) ???
ADC(GP40-47) ???
ONEWIRE ???
PWM ???
PWM Audio ???
DAC Audio ???
I2C Audio NO?
VS1053 Audio ???
LCD ???
LCDPANEL I2C NO?
LCDPANEL SPI ???
LCDPANEL Parallel ???
TOUCH ???
COUNT(FIN,PIN,CIN) ???
IR ???
IR SEND ???
TEMPR
HUMID
RTC (I2C) NO?
DISTANCE ???
KEYPAD ???
WS2812 ???

-Carl

matherp
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Posted: 02:41pm 19 Mar 2025

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If I can fix a current limitation everything will work on all pins except VGA and I2S on VGA firmware versions. I've just got I2S working on GP33,GP35 under HDMIUSB. I now need to try and rework the rest of PIO functionality to behave the same although the current PIO interface may limit my success on that so user PIO on pins above GP31 may not be possible.

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