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Forum Index : Microcontroller and PC projects : Raspberry Pi Monitor doesn't work with PicoMiteHDMI
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| matherp Guru  Joined: 11/12/2012 Location: United KingdomPosts: 10224 |
That's not what the AI says |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5050 |
Ai-ai-ai, Sorry, Peter, I think I believe facts, not Ai... I started out reading datasheets of actual chips, that exist in silicon. But Ai will get better with time... Volhout Edited 2025-02-10 02:18 by Volhout PicomiteVGA PETSCII ROBOTS |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7852 |
Strangely enough I was thinking of this at stupid o'çlock this morning. I came to the conclusion that the HSTX was definitely not intended for DVI as it isn't open drain/collector. Well, probably not anyway. As it has no input mode you can't switch its pins into that to make the outputs high impedance - the pullup is always active. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5050 |
Peter, Finally got around testing the PicoGameHDMI on my large screen Philips TV. Tried the latest b10 (today version). Initially 640 worked okay, I could play "rocks" in mode 1. And edit. Then I tried 1024 resolution, and I got a prompt mid screen, and could open the editor. The function bar was in the middle of the screen. As if the vertical sync was lost. This did not recover, not even when I repowered the pico and re-selected the source on the TV. I tried 1280, and no picture. Then I tried the 12mA drive strength test program (1 page back). That confused the TV. There was colored stripes in 1280 mode, but nothing made sense. When I switched back to 1024, the same colored stripes. No prompt, no visible edit screen. And even when I switched back to 640, there was a prompt, but it was mid-screen (left side, but mid screen). So the 12mA was not a solution for my TV. But even when I cold booted the pico, the TV would not have joy with 640 anymore. I think something in the TV was mis aligned/off-tuned. Anyway.. no fun. When I plugged in the laptop in the same HMDI, I immediately got a good picture. There maybe something in the PicoGameHDMI board. I will start to investigate. Just to make sure I have not broken anything. This is just a report, not a request for any SW change. I have to find the culprit first. I hope I did not invert the clock or something, or the 12mA program needed to run while the HDMI was disconnected from the TV, since it changed 1 wire in a pair, just a few usec before it changed to other wire in the pair. And that may have confused the TV. Volhout EDIT: checked all the wiring, and it complies with OPTION HDMI PINS 5,2,7,0 (as set up before) so back to basics. Appart from the 640 mode with mid screen prompt, nothing works anymore. So sad... Edited 2025-02-12 07:41 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5050 |
Peter, I found part of the issue.. OPTION RESOLUTION 640,252000 works The TV does not like the 75 Hz frame rate. Also with 12mA drive strength this works. Now I have to research if I can change the other resolutions also to a frame rate the TV likes. Something like 50Hz. But that is for tomorrow.... Volhout Edited 2025-02-12 07:46 by Volhout PicomiteVGA PETSCII ROBOTS |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10224 |
Forget the drive strength. B10 is set to 8mA and that appears to be enough for anything. NB: the default is 4mA and the RP2040 HDMI code that was referenced is only using 2mA. 1024 and 1280 both use 60Hz which is the standard. There is no 50Hz version of either. Why not start with a monitor which will most likely work, satisfy yourself that the wiring is OK and only then try the TV when you have eliminated other variables |
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stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2533 |
er peter sir. this has got complicated unnecessarily as the original hdmi on pico 2/2350 worked ok. I doubt many users have a monitor with hdmi.. tvs maybe. tv hdmi works but higher res on one tv I got no signal... but most ok and 640x480 is always ok. using olimex 2040 breakout board and hacked stripboard with hdmi breakout board. stan... my sympathy if it don't work for users... it should |
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| Amnesie Guru Joined: 30/06/2020 Location: GermanyPosts: 622 |
?!?!? HDMI is standard on all new / modern monitors. Haven't seen one without! But apart from that; I am glad that VGA is still "a thing" today and almost always on every new monitor.  Greetings Daniel |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7852 |
I'm suspecting that increasing the drive current value doesn't increase the current but might reduce the source resistance of the Pico. With a 220R resistor in line and a 50R load the maximum you can get from the Pico would be 12mA, with a zero source resistance and no cable and connector losses. The sensitivity of the HDMI input is 150mV across 50R, I understand, so that's 3mA for full drive. 4mA drive current setting should be fine under any circumstances. However, if I'm right, increasing the setting might be helping the slew rate when driving the cable capacitance. That might be making a difference. ----------- Yep, sorry Stan, but you can't really get a computer monitor without at least one HDMI input unless it has Display Port socket(s). Or both. :) VGA is often included as it costs almost nothing to do so nowadays. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5050 |
I have to keep using 640,252000. Monitor... yeah... I do not have one yet (shame ?). Laptops, and a MAC (screen is built in). The only monitor I have with HDMI is built in into a system which uses it for VGA. And it is 1024x600. Not a good investment I guess. It won't do 1024x768, and won't do 1280x720. And I have an ancient 5:4 LCD VGA screen (1280x1024) that supports 640x480. Time to invest in a new monitor I guess... Volhout EDIT: OK. I found it. The HDMI standard supports only 60Hz. There was a broadcast video standard 480i and 480p that where 50Hz, and these where upscaled to 640x480 @ 60Hz when using HDMI, and scaled different for SCART. 1080p and 720p where always 60Hz. 1080i and 720i are 30Hz. Edited 2025-02-12 18:24 by Volhout PicomiteVGA PETSCII ROBOTS |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10224 |
I've done more research on this. Basically the PicoMite firmware supports DMT (Display monitor timings) There are another set of video timings CEA (Consumer Electronics Association) If you look at https://tomverbeure.github.io/video_timings_calculator you can enter 1280x720x60Hz and in the DMT column you will see the timings I use. You could enter 1280x720x50 and you will see in the CEA column a completely different set of timings including different synch polarities. Someone previously suggested I could reduce the required overclock for 1280x720 by using one of the CEA compressed timings. I did try this but none of my monitors would work with other than the DMT settings. As with the USB gamepad discussion, there is a limit to what a 1$ single chip system can be expected to support and it is not realistic for the system to read the monitor/TV capabilities and then configure itself accordingly, including changing the CPU speed. I current support 640x480x60 DMT (252000) 640x480x75 DMT (default) 1024x768x60 DMT 1280x720x60 DMT with the timings given in the calculator |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7852 |
Are there really limits on what a 1$ single chip system can do? You could have fooled me, Peter.  Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5050 |
Hi Peter, Interesting stuff. In the timing calculator you do not get a proposal for 1024x768x60 for CEA-861. Apparently that has not been in the consumer electronics standard but it is DMT (or the calculator is not perfect). This document describes 1280x720x60 (format 4) and 1280x720x50 (format 19). The timing difference is only in horizontal timing (1980 clocks versus 1650 clocks) where the difference is in the hsync time between pixels and start of sync. No sync inversions. I have no idea if my TV supports this, and I won't ask you to implement this. I just wanted to share knowledge. I will search for a nice monitor (I just used the TV in absence of alternative, and will never use it to develop code). CEA-861-B.zip Volhout EDIT: Page 14 (bottom page) specifies that 1280x720p -or- 1920x1080i is mandatory ("shall") for DTV monitors. In 50Hz countries that would be 1280x720p50 or 1920x1080i50. I guess your living room TV could also support that (UK is 50Hz)... Edited 2025-02-12 21:00 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Bleep Guru Joined: 09/01/2022 Location: United KingdomPosts: 625 |
Puerly as a referance point, I am having no problems with HDMI on any monitor or TV that I have, Using Peters Ref. design and the latest B11. A £17 (when I bought it) reversing monitor. as shown here Bought from here. 7" car reversing monitor A old Dell VGA monitor, E1715S, which I got for £10, driven by a HDMI to VGA dongle £4 Ebay. HDMI to VGA A fairly basic Samsung 40" TV, UE40MU6120K. A reasonable, but old, Dell Monitor UE2412M. In the early days I did see faint blue noise in some modes, especially the higher resolutions, mainly on the reversing monitor, and the Samsung TV. But now they are all crystal clear, even the cheap, second/third hand, VGA monitor. As an added bonus this latest version seem to be about 4 to 6% faster than 6.01. :-) Regards, Kevin. Edited 2025-02-12 21:46 by Bleep |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5050 |
Hi Kevin, I am looking out for a monitor since this morning. I am convinced my TV is not compatible. And I don't know why (is it YPrPb and not RGB in this mode, or is it not syncing at all, honestly I don't even plan to find out. It is not working, and I am buying a monitor), and leave the TV for what it is : living room entertainment. So I appreciate you informing us that others have no problems at all. Volhout PicomiteVGA PETSCII ROBOTS |
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| Bleep Guru Joined: 09/01/2022 Location: United KingdomPosts: 625 |
Hi Harm, As I've indicated, you can almost certainly get an old, but good quality VGA monitor & use the HDMI to VGA converter I indicated very cheaply, otherwise a good second hand monitor, which has HDMI, for probably not much more, people seem to 'have' to upgrade, so there are plenty around and cheap. The E1715S is a 5:4 ratio, so not ideal, but does up to 1280x1024, I'm certain you'll be able to find similar/better for not too much money, just the extra space it takes up. ;-) Regards Kevin |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2533 |
Shows how old my pc monitors are, none have hdmi only vga but 2 have dvi sockets. my laptop has hdmi and vga sockets and connecting a 42 inch tv to both and watching same film I can't see any difference. stan |
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| Exile Newbie  Joined: 27/05/2023 Location: United KingdomPosts: 28 |
That was me. The original RP2040 DVI code makes use of the CEA compressed timings, as it reduces the amount of overclock required when HSTX is not available. I've attached a zip of the 3 original test uf2s I created, together with the C file. The display types are: MODE_720_CVT MODE_720_CVT_RB MODE_720_CVT_RBV2 They all worked on my TVs and monitors, I guess it shows how variable the interpretation of the standard is between different display vendors! The display timings were calculated using the Video Timings Calculator that was mentioned 720uf2.zip |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5050 |
@Peter, May I do one suggestion for the HDMI DMT mode. If I read my own experience thread 6 posts back, I originally had 640 video on my TV, and later that did not work anymore. When started the picoGameHDMI board, there where no options programmed. I manually added all options. And since I did not see any option cpuspeed, I als programmed CPUSPEED 252000 (without thinking, that was the default I always used for VGA). That means that the HDMI was running at 640 60Hz (without me realizing). When I switched to 1024, later 1280, and finally back to 640 I could not get a good picture on 640. Resulting in confusion... Later, when trying 640,252000 I realized the default is 640,315000 (75Hz), and when using only 640, it uses 75Hz. So I was first time accidentally getting a pcture on 640 on that TV. Without knowing why. Others may get that confusion as well. Is it an option to default 640 to 60Hz. I think 60Hz is also DMT standard. Then that could also be the mode that is compliant with CEA without making any other tests and experiments for other resolutions. Let me hear what you think (you will, no doubt). Volhout PicomiteVGA PETSCII ROBOTS |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2932 |
1,000,000% agree. I am doing a LOT of HDMI testing currently and this still catches me out when switching back to 640. |
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