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ville56
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Joined: 08/06/2022
Location: Austria
Posts: 550

Posted: 01:01pm 11 Jul 2026

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Xian,

lets sort it out step by step, starting with the absolute minimum without the Olimex board.
Why: I also had some problems with cold solder joints on the Olimex board (but with the LiPo connector, so I only had a lightshow on the LED) and also had them once to the pins on the Pico board (but that was my own bad ...)

As I don't know your background, I'll try to do it very low level, so please don't get me wrong ...

- first, please check if the USB-serial adapter is set to 3.3V as the Pico may not like 5V on the pins without being powered up. This COULD destroy the pico. (I've done this 1000 times, never had any problem) But just for safety reasons, always make sure the pico is powered first and you are on the safe side.

- remove the Pico from the Olimex board and connect the USB-serial adapter to the default Pico console pins gp8(TX)/gp9(RX) to the repsective RX/TX pins and Pico ground to ground on the adapter e.g. with some Dupont wires.
- plug the Pico via a USB cable into an USB port on the PC
- plug the adapter into another USB port on the PC and note which COM port it creates
- press boot/reset on the Pico to invoke the bootloader
- flash the firmware (PicoMiteHDMIUSBV6.03.00.uf2)
- after flashing run and connect the terminal emulator to the virtual COM port noted before

you should get a concole prompt. If not, you could try reversing RX/TX on either the Pico OR adapter side, just one side.

If this does not give a prompt, you may try the plain version (PicoMiteRP2350V6.03.00.uf2). You may also flash any other (older) RP2350 version and try if it runs. Just take care not to use a Web version.

If it does respond, the Pico is well and the fault is probably on the Olimex board. If it doesn't respond, the serial port pins may have died if the heartbeat is blinking.

If you have a second Pico board, you can verify the setup with that ...

Let me know how things work out.

Gerald

73 de OE1HGA, Gerald

JanVolk
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Joined: 28/01/2023
Location: Netherlands
Posts: 385

Posted: 01:10pm 11 Jul 2026

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For an Olimex RP2040 Pico PC adapter board:
https://www.tinytronics.nl/nl/development-boards/accessoires/adapter-boards/olimex-rp2040-pico-pc-adapter-board-voor-raspberry-pi-pico.
Mount a Raspberry Pi Pico RP2350 onto the baseboard.
Load the version `PicoMiteRP2350HDMIUSB V6.03.00.uf2' via the standard RP2350 USB port.
After flashing, connect an HDMI screen to the Olimex board, a USB dongle or hub to the RP2350 USB port, and a USB power supply to the Olimex PCB (also connect the HDMI 5V link on the underside of the base PCB, if applicable).
Type the following blindly on the USB keyboard: `OPTION RESET OLIMEX USB` (Enter) `Y` (Enter). (The prompt `(Y/N)?` is not visible).
Then reset the board; you should see the display output on HDMI and COM1 (RX=GP1, TX=GP0), and it should work. This process may fail occasionally, so you might need to repeat it.
Afterward, configure the options to your preference. Have fun.

Jan.

Footnote added 2026-07-12 01:07 by JanVolk
I’ve experienced an issue where the first character sometimes doesn't register when using the keyboard.
This happened with TeraTerm, but could it possibly be related to the USB keyboard, causing the input to fail?

ville56
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Joined: 08/06/2022
Location: Austria
Posts: 550

Posted: 02:28pm 11 Jul 2026

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Before option reset please set your keyboard language if not english with

OPTION KEYBOARD GR (e.g. for german) as the Y for the yes is otherwise located differently.

73 de OE1HGA, Gerald

Xian
Newbie

Joined: 19/03/2025
Location: Germany
Posts: 39

Posted: 03:46pm 11 Jul 2026

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Thanks a lot to all the advisors! Fantastic team!

to cut a long story short, i have a working 6.3.00 HDMI/USB environment running on the Olimex board.

However, non of the "ways" worked while the pico2 was connected to the board.

In the end i removed the pico2 from the Olimex board, nuked it again, installed the v6.03.00 HDMI/USB and powered down.

Then i connected an ftdi pcb to gp8/gp9 and could connect to the PC (i used minicom on my Linux box). I then entered the command "option reset olimexusb" and immediately the reason why that did not work before became obvious. There is a security hint "all data will be lost, also on drive A: - continue?" (may not be literally correctly quoted). Entering a "Y" and the reset began.
Powered off again, plugged the ftdi pcb to gp0/gp1, re-powered the board and connected the ftdi with my pc to see there is a reply now.
Then i removed the ftdi from the pico2, plugged the pico2 into the Olimex board, re-powered again and immediately there was an HDMI signal. And the ftdi connected to gp0/1 (soldered to the Olimex board) worked like a charm. Also the USB-keyboard connected to the pico2 USB worked immediately.

I have no clue why the gp8/9 ftdi connection did not work while the pico2 was inserted in the Olimex board directly after flashing the new firmware. Outside the Olimex board all worked fine. Maybe that is due to a usb hub, too low power, whatever. I have a working path now and my frustration has gone immediately. To point out clear, i have two FTDI boards connected to the Olimex board. One is on gp8/9 (UEXT), the other on gp0/1. They both worked while i had the old version installed (8/9 initially, 0/1 after option reset olimexusb).

Thanks again for all your help and of course thanks to Peter for the wonderful Basic! And sorry for my frustration.

Regards,

Xian

Xian
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Joined: 19/03/2025
Location: Germany
Posts: 39

Posted: 05:20pm 11 Jul 2026

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JanVolk said ...
Type the following blindly on the USB keyboard: `OPTION RESET OLIMEX USB` (Enter) `Y` (Enter). (The prompt `(Y/N)?` is not visible)...

Hey Jan,

that was exactly my fault. i did not know that there was a prompt. As for the "old version" (6.0.02) i did not have to enter the "Y".

And also that no USB connection gp0/1 and gp8/9 did work in the way that anything was echoed.

But now i have it running.

Thanks a lot,

Xian

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8947

Posted: 05:32pm 11 Jul 2026

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The FTDI board they you have may be objecting to the pullup resistors (that you can't isolate) on GP8 and GP9 of the Olimex board. Also, some of the USB-TTL converters have 5V outputs that you can't change. That can trigger problems in the RPnnnn that prevent it from booting.

It is rarely straightforward getting MMBasic to run satisfactorily on hardware that's designed to support only Python and C#. I, personally, never recommend it unless someone is doing it for the challenge. There are simply too many compromises to be made.

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

Xian
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Joined: 19/03/2025
Location: Germany
Posts: 39

Posted: 06:31pm 11 Jul 2026

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Mixtel90 said The FTDI board they you have may be objecting to the pullup resistors (that you can't isolate) on GP8 and GP9 of the Olimex board. Also, some of the USB-TTL converters have 5V outputs that you can't change. That can trigger problems in the RPnnnn that prevent it from booting.

Hi Mick,
that may well be, however, they work when the system is once correctly setup.

But one question regarding the 5V, should the ftdi be set to using 3.3V when connected to the Pico2 or the Olimex board? The ones i use do have a jumper to move from 5V to 3.3V, and i have them on 5V. So should i better switch to 3.3V?

Thanks and regards,

Xian

ville56
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Joined: 08/06/2022
Location: Austria
Posts: 550

Posted: 07:10pm 11 Jul 2026

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3.3 V is the value to use

Gerald

73 de OE1HGA, Gerald

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8947

Posted: 08:16pm 11 Jul 2026

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Hehe....
In theory you can use 5V for the Pico 2 and anything else based on the RP2350 *provided that the IOVDD supply to the chip is at least 3V3*. The RP2040 shouldn't really get 5V on its pins. However, provided the current is limited by, for example, a weak pullup, you will usually be ok.

The Datasheet for the chips indicates which pins will officially withstand 5V. The ADC pins and some others won't. Some will but only under specific circumstances.

Just be safe and *always* use 3V3 around the Pico family. :)

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

Xian
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Joined: 19/03/2025
Location: Germany
Posts: 39

Posted: 12:21pm 12 Jul 2026

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Mixtel90 said ...
Just be safe and *always* use 3V3 around the Pico family. :)

Thanks Mick, i've set it to 3.3V now and so far no difference after installation. As i'm just done with the upgrade, i'll keep that in mind and see, if there is a difference in the upgrade cycle (new firmware).
Best regards,
Christian

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8947

Posted: 12:57pm 12 Jul 2026

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It shouldn't make any difference really. The voltage levels for 1 and 0 with a 3V3 supply are within the tolerance of those for a 5V supply.

I think what you are doing by changing the switch to 3V3 is preventing the ESD protection diode on the RPnnnn from going forward-biased and pulling up the voltage on the RPnnnn VDD line to an unknown and saggy level via the pullup resistors. The RPnnnn tries to get a stable supply for its clock and fails.

I've had RP2040's boot perfectly well with pullups to 5V on the USB-TTL converter so I don't think it's an exact science, though I'm pretty sure it must stress the chip just a bit. :)

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

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