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

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matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 9567
Posted: 02:52pm 13 Feb 2025
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Most people want the extra speed and most people have monitors that accept 75Hz so it stays as-is. It has never come up as an issue until the over-priced, underperforming Pi monitor issues surfaced. Harm will be happy as soon as he has a proper monitor and won't think about it again. The functionality is there for 60Hz so you only need to remember to use it. The default is good for nearly everyone.
 
Volhout
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Joined: 05/03/2018
Location: Netherlands
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Posted: 03:18pm 13 Feb 2025
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Hi Peter,

I am not sure this is the right decission. Basic comptibility is key. Upgradability (other resolutions/higher framerate) is luxury, but will never be appreciated when the basic compatibility is not guaranteed.

But I will shut up about this topic after this post. I have poluted enough posts on this forum about HDMI.

Volhout
PicomiteVGA PETSCII ROBOTS
 
stanleyella

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Joined: 25/06/2022
Location: United Kingdom
Posts: 2323
Posted: 04:21pm 13 Feb 2025
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  Volhout said  Hi Peter,

I am not sure this is the right decission. Basic comptibility is key. Upgradability (other resolutions/higher framerate) is luxury, but will never be appreciated when the basic compatibility is not guaranteed.

But I will shut up about this topic after this post. I have poluted enough posts on this forum about HDMI.

Volhout


if it works for me then look at this image , head turned right 90 d


Edited 2025-02-14 02:27 by stanleyella
 
Bleep
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Joined: 09/01/2022
Location: United Kingdom
Posts: 539
Posted: 07:36pm 13 Feb 2025
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Not funny Stan.
 
Amnesie
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Joined: 30/06/2020
Location: Germany
Posts: 465
Posted: 09:44pm 13 Feb 2025
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Stan, ...

why so aggressive?
 
robert.rozee
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Joined: 31/12/2012
Location: New Zealand
Posts: 2380
Posted: 11:45pm 13 Feb 2025
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i presume the image posted by stanleyella has some deeper meaning?

i must confessed, i am not entirely impressed by the DVI performance of the RP2350 chip - i get the feeling that support for DVI was just a step too far for the chip's limited resources. certainly, Peter has done a sterling job at coaxing out as much as is possible from the limited hardware, but at the end of the day it seems the RP2350 is just not capable of producing a totally compatible output signal that works for everyone.

i always think back to the RPi model A+, equipped with an onboard full-sized HDMI port that DOES work. but, alas, the current RPi offering - the zero - is crippled by a micro-HDMI socket.


cheers,
rob   :-)
 
WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2883
Posted: 12:42am 14 Feb 2025
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  robert.rozee said  …. i must confessed, i am not entirely impressed by the DVI performance of the RP2350 chip - i get the feeling that support for DVI was just a step too far for the chip's limited resources.


Neither was I too impressed after my initial attempts BUT as of now I think Peter has made DVI very usable. Sure, there are limitations, but when those limitations are understood then some impressive results are possible.

I don’t think I’m wrong in saying that we have all learnt something on the recent ‘journey’. Having spent many hours/days/weeks deep-dive testing I can see why some people have ‘struggled’.

Personally, I have seen jitter/noise but that was down to long cables and slow slew rate. I have had monitor and TVs not display an image, but that was down to incompatible frequencies (and slew rate). Also not helped by when changing resolution to 640, most monitors I have here only work on 60Hz whereas the default 640 res is 75Hz.

Thrown j to the mix, there is the 5V on pin 18 that some displays want; not to mention potentially needing to set OPTION HDMI PINS depending on your hardware pinout of the 4-pairs in the DVI connection.

As for the OLIMEX 2040 Pico PC board there are mixed feelings (mostly negative) about it. Once again, understand its limitations and you can use it very easily. Currently I have two test beds set up with them to give me easy HDMI and SD connections. I have left out GP26,GP27, GP28 (ie, the onboard audio) and instead connected an I2S board (and playing sound files from the SD).

Other than some basic ‘polishing’ in the firmware, I am very impressed with DVI usage.

The ultimate would be to be able to display full colour photos at 1280, but I do live in the real world and know some things would be a little to much stretch of the hardware capabilities.

So, personally, I truly like the current DVI capability and would recommend it to anyone asking if it is any good.
For everything Micromite visit micromite.org

Direct Email: whitewizzard@micromite.o
 
TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6160
Posted: 02:04am 14 Feb 2025
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To add my experiences to the compatibility list.

My 3 monitors available for testing all worked on all modes.

I connected my birds-nest board to the main TV via a 10 meter amplified HDMI cable. All modes worked without any sign of problems.

I also tried connecting via a HDMI input DTV modulator.
That is how I normally connect my PC to the TVs.
All modes failed.
I wasn't expecting any success.
That modulator is at the cheap and nasty end of the range.

I do have a more advanced modulator but the effort of removing it from service to test is not worth it.

Finally,
I have a USB HDMI video capture device which was happy with all modes.

Jim
VK7JH
MMedit   MMBasic Help
 
mozzie
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Joined: 15/06/2020
Location: Australia
Posts: 78
Posted: 07:06am 14 Feb 2025
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G'day,
This post was intended to be an update on further testing of DVI/HDMI, but Mr Murphy has put paid to that idea...
Sometimes you just gotta pack it in and have a laugh at everything  

So currently working night shift 150km from home, however during a trip home to pick up parts I threw together the device shown at right of the pic below, the mess on the left has been used in most testing to date as a worst case scenario for DVI signals.




Whilst not pretty the new (right) unit plugs straight in to the DVI sink and "should" be more stable.

HOWEVER, even though the PICO2 units came next to each other in the same carrier strip, the new unit will not go past 252mhz reliably, even on the standard RP2350 firmware, it tries but reset loops every few seconds. At 252Mhz it is stable and delivers 640 DVI perfectly. So much for more testing at higher resolutions

This is NOT a winge or complaint, but it does show that we are pushing the PICO pretty hard and even genuine units are not gauranteed to play well all the time.

The fact that DVI/HDMI works at all on this hardware is awesome.
The fact that it'll work at 1280x720 on my breadboard mockup is incredible, just plugged it into the TV in my donga (living unit / cabin) and 1280 works fine, no 5V or 10k resistors required (on this one anyway)

My thanks once again to Geoff, Peter and everyone else involved in getting this little marvel to where it is now  

Regards,
Lyle.
Edited 2025-02-14 17:21 by mozzie
 
Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 7151
Posted: 08:37am 14 Feb 2025
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:)
The poor little RP2350 is *way* out of spec when producing DVI. It's a credit to it's designers that it seems to be able to take such abuse without releasing the magic smoke. Both the RP2040 and the RP2350 are vastly underrated by many.
Mick

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Preliminary MMBasic docs & my PCB designs
 
matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 9567
Posted: 09:02am 14 Feb 2025
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It is possible to get HDMI with the Pico2 in spec: 640x480@60Hz with a 126MHz clock. But at this speed there isn't enough processing time in the interrupt routine to do any of the fancy things like layers so I haven't included it. The VGA RP2040 still supports 126MHz but has the same restrictions so things like Petscii can't run at that CPU speed.
 
stanleyella

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Joined: 25/06/2022
Location: United Kingdom
Posts: 2323
Posted: 04:22pm 14 Feb 2025
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hdmi works with carp wiring as above post

 
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