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Forum Index : Microcontroller and PC projects : Raspberry Pi Monitor doesn't work with PicoMiteHDMI

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Amnesie
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Joined: 30/06/2020
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Posted: 11:20pm 01 Feb 2025
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Hello,

is it normal that some HDMI monitors like the original (new released) Raspberry Pi monitor doesn't work with the PicoMite HDMI version?

I just tried the newest HDMI Beta, on my OLD Acer VGA/DVI monitor everything works fine, but on modern (?) TV & the new Raspi-Monitor it does not work.

Also on my new TV with HDMI the PicoHDMI does not work. I guess the monitor has to support DVI.. but isn't DVI the same as HDMI but without audio channels? Hmmm.


Greetings
Daniel
Edited 2025-02-02 09:20 by Amnesie
 
Peter63
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Posted: 03:52am 02 Feb 2025
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  Quote  I just tried the newest HDMI Beta


Did previous PicoMite HDMI version work?

/Peter63
 
Mixtel90

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Joined: 05/10/2019
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Posted: 08:07am 02 Feb 2025
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I have monitors that do and don't work with DVI from the Pico. Generally they all work at 640x480 but start to fall apart as the resolution increases.

DVI is a subset of HDMI that *can* use the same connector (it doesn't have to, there is a DVI connector). HDMI can do a lot more.

The first thing to check is that your Pico board is putting 5V on pin 18 of the HDMI and that pin 19 is pulled up to 5V by a resistor. Some monitors insist on this, others don't care. It doesn't always work.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
Amnesie
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Posted: 11:53am 02 Feb 2025
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  Peter63 said  
  Quote  I just tried the newest HDMI Beta


Did previous PicoMite HDMI version work?

/Peter63


No version works. It depends on the minitor / TV.
 
Amnesie
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Posted: 11:56am 02 Feb 2025
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  Mixtel90 said  I have monitors that do and don't work with DVI from the Pico. Generally they all work at 640x480 but start to fall apart as the resolution increases.

DVI is a subset of HDMI that *can* use the same connector (it doesn't have to, there is a DVI connector). HDMI can do a lot more.

The first thing to check is that your Pico board is putting 5V on pin 18 of the HDMI and that pin 19 is pulled up to 5V by a resistor. Some monitors insist on this, others don't care. It doesn't always work.


Hello Mixtel,

thank you for this hint, but sadly this doesn't work either. I have the Adafruit DVI Breakout and installed the 10k resistornetwork + connected 5V+ via schottky diode. Nothing. It seems to be highly monitor/ tv - dependable. Hm! This confirms to me that I should stick with the VGA version  

I mean.. It works on some monitors and TVs but when it is HDMI / DVI it should work on ALL.


Greetings
Daniel
Edited 2025-02-02 21:58 by Amnesie
 
javavi

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Posted: 12:07pm 02 Feb 2025
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I understand it this way, that not all modern HDMI monitors accept DVI video signal (without sound). And vice versa, HDMI signal (with sound) is not accepted by monitors with DVI video input.
 
javavi

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Posted: 12:07pm 02 Feb 2025
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I understand it this way, that not all modern HDMI monitors accept DVI video signal (without sound). And vice versa, HDMI signal (with sound) is not accepted by monitors with DVI video input.
Edited 2025-02-02 22:09 by javavi
 
matherp
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Posted: 12:25pm 02 Feb 2025
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HDMI works on every "normal" monitor I own. HDMI is supposed to be backwards compatible with DVI so if it requires things outside of the DVI spec then that is a problem. Of course, a monitor that isn't widescreen will have a problem with 1280x720 but other than that there shouldn't be an issue. If you are having a problem just buy a cheap second hand Dell 1080p monitor and you won't have an issue.
 
Amnesie
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Posted: 01:03pm 02 Feb 2025
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  matherp said  HDMI works on every "normal" monitor I own. HDMI is supposed to be backwards compatible with DVI so if it requires things outside of the DVI spec then that is a problem. Of course, a monitor that isn't widescreen will have a problem with 1280x720 but other than that there shouldn't be an issue. If you are having a problem just buy a cheap second hand Dell 1080p monitor and you won't have an issue.


The whole point of HDMI (for me) is not to buy old stuff. And the Raspberry Pi Monitor, which is newly released, should do HDMI without any problems. And then I found out that my TV (bought half a year ago) doesn't work either on HDMI with PicoMiteHDMI.

So I suppose some new (??) monitors and tv's have problems with it - for what reason I don't know. I have monitors (old ones) and cheap portable HDMI screens that work with picoMiteHDMI, but it is not the point for me to find one that works, but that (as it seems) some new HDMI monitors have problems.

Of course I have only TWO devices which have problems and this isn't representing ALL new products. It was only a question what the problem could be  

Greetings
Daniel
Edited 2025-02-02 23:04 by Amnesie
 
robert.rozee
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Posted: 01:29pm 02 Feb 2025
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is there any chance of loading something other than MMbasic onto a pico to check if the problem is related to something in MMbasic or is instead a problem with the DVI over HDMI hardware built into the RP2350?

having said this, i would expect a Raspberry Pi Monitor to have been tested by the RPi folks against a RP2350.


cheers,
rob   :-)
 
matherp
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Posted: 01:50pm 02 Feb 2025
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Amnesie

Have you tried any resolutions other than 640x480? Please try and report.
 
javavi

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Posted: 02:04pm 02 Feb 2025
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  robert.rozee said  is there any chance of loading something other than MMbasic onto a pico to check if the problem is related to something in MMbasic or is instead a problem with the DVI over HDMI hardware built into the RP2350?

Knowing the detailed pinout of your equipment, I can assemble a NES emulator project for Pico with HDMI video output and sound. I am sure that it will work, because there was already such a precedent.
 
javavi

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Posted: 02:04pm 02 Feb 2025
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  robert.rozee said  is there any chance of loading something other than MMbasic onto a pico to check if the problem is related to something in MMbasic or is instead a problem with the DVI over HDMI hardware built into the RP2350?

Knowing the detailed pinout of your equipment, I can assemble a NES emulator project for Pico with HDMI video output and sound. I am sure that it will work, because there was already such a precedent.
 
Mixtel90

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Posted: 02:07pm 02 Feb 2025
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There are several possible problems

Some HDMI displays want dual-link signals and the PicoMite doesn't provide them.
Some DVI-HDMI leads and adapters only work from HDMI to DVI, not the other way round (even when badged as bi-directional).
If a display is expecting DVI-I rather than DVI-D then it won't work. This is rare though as DVI-D and HDMI convert easily and DVI-I is analogue.
If your display has HDMI and DVI sockets then try unplugging the HDMI input when using DVI. Sometimes the sockets are interlinked.

There's nothing like a standard...
Mick

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

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Joined: 25/06/2022
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Posted: 02:11pm 02 Feb 2025
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I use pico 2 hdmi usb on strip board and an Olimex 2040 board with pico 2 2350 fitted.
no extra 5V added and all works on all tv's and car reversing monitor at all resolutions. not actually tried pico hdmi to a dvi socket on computer monitor. I don't have a pc monitor with hdmi just vga and dvi and haven't a hdmi to dvi cable.
I thought dvi was hdmi without sound.
 
Volhout
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Posted: 02:22pm 02 Feb 2025
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I do not own a RPi monitor, but I know that my 7" monitor has a flaw. May not relate to your situation, but you may try.

My 7" monitor will not select source automatic (VGA/HDMI), you need to use the setup menu to select. But you cannot get into the setup menu without a video signal present (either VGA or HDMI). So you must connect a source before you can select it.

TV's and some monitors auto select, but they use CDC to communicate. And Pico HDMI does not support CDC, nor I2C. So you will have to manually select source.

Volhout
PicomiteVGA PETSCII ROBOTS
 
stanleyella

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Posted: 03:47pm 02 Feb 2025
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my tvs have a source button and a list of hdmi, vga, avi etc.
never seen one that detects the source but most auto adjust the source selected to fit the screen and frequency
 
Amnesie
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Posted: 04:01pm 02 Feb 2025
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  matherp said  Amnesie

Have you tried any resolutions other than 640x480? Please try and report.


Hi,

Yes, I tried ALL available resolutions, none of the works. On both (Raspberry Pi 15,6" Original Monitor and my TV) the source is somehow detected, but the screen is black (but illuminated from the backlight led). Selecting the Source via menu isn't possible with the Raspberry Pi Monitor, since there isn't any menu (only auto detect). On the TV it is (this is an assumption) also somehow detected, because my TV normally jumps back if there is no signal recognized, but it stays on "HDMI-1" (but nothing than a black screen).

I tried the original HDMI release from geoff.net, as well as the latest beta from forum here. All the same issue. Tried "hotplugging" tried also to power on with everything "pre-attached".

But here is something that I find interesting:

I tried the following:

Using PicoMiteVGA with an HDMI-active adaptor (so it is VGA-TO-HDMI) it is also not working (exaclty the same behavior, somehow "recognized" but black screen). But it is interesting that VGA-TO-HDMI works in general on all my other HDMI monitors and TVs I've tested (yes with picoMiteVGA! - which is cool!). I didn't expect that...

My setup is 100% like in the manual (page 29) so it is default. And as said, it is working, but not on the two mentioned devices. This just kept me wondering if there is
an obvious solution to this.  

Greetings
Daniel
Edited 2025-02-03 02:03 by Amnesie
 
Peter63
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Posted: 04:32pm 02 Feb 2025
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Good discussion about this... You want to find the reason why it doesn't work. Sometimes you find the cause and sometimes it has to depend for a while.

As Mike said
  Quote  There's nothing like a standard...


/Peter63
 
matherp
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Posted: 04:50pm 02 Feb 2025
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Based on your description I would suspect an electrical issue. The Pico cannot generate electrically correct signals. The 220/270 ohm approach is a cludge.
It looks like for some reason your devices are not accepting the data as as valid but are seeing the sync.
Does the Raspberry screen allow you to interrogate the signal characteristics, timings etc.? What does it show?
 
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