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Forum Index : Microcontroller and PC projects : Why VGA and not DVI/HDMI
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| matherp Guru  Joined: 11/12/2012 Location: United KingdomPosts: 8567 |
Lewis I don't know why you keep re-opening this. There is no-one on TBS who is going to implement DVI on the RP2040. Flash can only be erased in 4K chunks each taking milliseconds to action making it useless for anything other than static pictures Default QSPI bandwidth on the RP2040 31.25MHz. Bandwidth required for 720p 74.25MHz |
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| KD5ZXG Regular Member  Joined: 21/01/2022 Location: United StatesPosts: 53 |
I thought video output required PIO/DMA from internal memory anyway. Unlikely that trick could read QSPI then make a u-turn and come out GPIO. Now for the hypothetical ridiculous question! Could such a frame divide across three or four synchronized picos, each serving one bit of color? Just asking in theory, not suggesting waste actual time working on it. Edited 2022-01-31 03:54 by KD5ZXG |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Hey Lewis, not knowing what kind of a budget you have for this but There's this option. Craig |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
How hypothetical? lol Yes. it can be done. One colour each. It'll run like a very slow slug on downers and be suitable for static displays only. And you'll have to write the software for it. :) You *can*t pump moving, high-res graphics out of a chip with no hardware GPU. It ain't gonna happen. "Ye cannae' change the laws of physics, Jim!" And remember that a demo, even with what appears to be moving graphics, is not a real life application. Things are different when you have to fit a high level programming language, variables and user program space in as well. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9051 |
QSPI is a very interesting and fast interface, as I have been reading, but it is still nowhere near fast enough to deal with digital video bitrates. I don't know about the rest of you, but even if it WAS possible by changing to a 16Mb QSPI chip, I'm not exactly thrilled by the idea of having to remove and swap the tiny QSPI memory chip on the Pico.  On inspection of a Pico module under my microscope, the QSPI chip fitted to the Pico module is a QFN package, and they are extremely hard to hand-solder, and are pretty much never done. Robert Rozee' will remember when he and I were prototyping the E28 module, we used a QFN 170 chip in the prototypes, and they were a total bitch to hand-solder, so the idea of doing that on that tiny QFN memory chip on the Pico - ahhhh......no thanks.  At this point in time, I think most of us can pretty much agree that DVI or HDMI is simply never gonna happen on the PicoMite - ever. Full stop. End of story. VGA or nothing. If you want DVI or HDMI badly enough, you will have to develop a way to do it yourself. Something I don't think many would be willing to do, due to the complexity. It's an interesting discussion though, but I think it is fair enough to say it will never happen on the PicoMite. Remember also, that a GPU such as the one on the bigger Raspberry Pi's, has dedicated VRAM(Video RAM) which is super fast, and there is a reason why VRAM exists, or they would have just used standard RAM. Smoke makes things work. When the smoke gets out, it stops! |
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lew247 Guru Joined: 23/12/2015 Location: United KingdomPosts: 1676 |
I just realised something - Sorry I should have made this clear at the start. I think everyone thought I meant DVI VIDEO?? I'm not interested in video I'm talking about the ability to display images at 720P(1280 x 720) and NOT video This would allow modern monitors with hdmi/dvi inputs and even old tv's such as 32 inch that a lot of people are scrapping be used as a large monitor for Picomite. I'm sure there's lots of people with projects that would like to be able to be used on a screen larger than 3.5 inches or vga monitors with higher than 320X480 in colour? Peter if you tell me this is impossible I'll give the idea up but you said yourself Flash can only be erased in 4K chunks each taking milliseconds to action making it useless for anything other than static pictures If it's a program it's displaying, or an image loaded from the internal flash or SD card superimposed (blit?) with information from a running program surely it doesn't matter if it takes milliseconds to load? From the manual PicoMiteVGA Features The VGA output is 640x480 pixels in the monochrome mode or 320x240 pixels in the colour mode with 16 different colours available (one bit for red, two bits for green and one bit for blue). These display perfectly on a normal VGA monitor) The reason I used the Pi for Picromite when it was working was partly for the inbuilt wifi but Mainly because it could be output on standard monitors and not just the tiny displays that were used before up to 7inch ones This is only USD1.95 or GBP2.45 in the UK   |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
You still need somewhere to store the picture and software to read it from there and squirt it out to the display board. If you go to the trouble of changing the on-board QSPI chip then it's no longer a Pico and no-one is going to support you. You could also (if you have enough pins) use an external static ram chip, but serial interface RAM might not be as fast as you'd like. Otherwise you're stuck with the 30-odd k of frame buffer that MMBasic knows about. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| lew247 Guru Joined: 23/12/2015 Location: United KingdomPosts: 1676 |
I'm not on about changing the QSPI chip, I only went down that direction when people started talking about memory and I don't want or need video An image can be read from an SD card if needed I'm talking about doing the same as the VGA version does just with a higher res Edited 2022-02-01 02:46 by lew247 |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 8567 |
And I'm saying no it's not going to happen but the source is online and "open" so anyone can do what they want Edited 2022-02-01 03:09 by matherp |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3649 |
How? Higher res = more bandwidth & more RAM. Where are you getting them? You may get them if/when a bigger Pico ships. John |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
Even with pics stored on the SD card, you still have to have the whole pic in ram somewhere to be able to scan it and pump it out to the adapter. It doesn't matter if it's a still pic or a moving one, a moving pic is only a series of still pics. The ram has to be fast to read so you can't dangle it on a serial interface. There's probably nothing spare in the PicoMite, I suspect that Peter's squeezed things to get the frame buffer that he has. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2285 |
hi Lewis, why not just use a RPi Zero? these have HDMI on board, and are inexpensive. they can run Tom's port of MMbasic, which has been coming along nicely and i expect will reach the point where it will do everything you are wanting. if you compare the cost of a pico + HDMI adapter + PCB + housing, i expect it will be similar to the cost of RPi Zero + standard/cheap zero case. cheers, rob :-) Edited 2022-02-01 06:31 by robert.rozee |
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thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3831 |
Hey Rob, whilst I appreciate your confidence, please humour me and don't make promises I may not be able to cash . I imagine that even with Peter's code for the PicRomite and (hopefully) MMB4W to cannibalise getting monitor display out of MMB4L is 12 months or more away; it's not currently a priority.Best wishes, Tom Edited 2022-02-01 20:40 by thwill Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
In fact, why not use a RPi anyway, if you want to display high res images? They could be stored on a USB stick on the Pi and selected from the PicoMite by sending commands over I2C or something. There's no reason why the PicoMite should have to handle them directly. If you wanted to do something a bit special you could use a bluetooth board on the PicoMite and select the images by sending commands using that instead of hard-wiring. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2285 |
you already have it talking to the linux terminal, and as long as you don't do anything too fancy this means MMB4L should run without any windowing GUI (ie, the 'text' screen you see when you press ctrl-alt-f1. return to the GUI with ctrl-alt-f7). from here it is relatively simple to manipulate the frame buffer directly and draw lines, fill areas, place text in arbitrary locations, etc. under Linux, you get all this stuff for free. a quick boot without launching the desktop/GUI, but access to a linear frame buffer. i suspect JohnS knows more about this than me, and can elaborate further... cheers, rob :-) Edited 2022-02-01 21:57 by robert.rozee |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3649 |
I suspect I don't - I've never had reason to do it. Sorry. John |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3831 |
I've had a very brief look, it doesn't look so difficult after all ... it's still not a priority though, sorry  .Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Hey Mick  This is precisely what I do with Android devices. One couldn't ask for more: Inexpensive Easy to program Battery power so no need to reboot after a power glitch Graphics processor High performance CPU Plenty of memory and storage High resolution touch screen Can utilise a mouse/keyboard Audio/video BT WiFi Easy remote access (I prefer TeamViewer but there are many options) Already packaged and many have rugged external protectors available. The list goes on and on. Craig |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3010 |
I think the images that Lewis wants to display are not rapidly changing, but also not pre-built, so the Picomite would build the image (maybe as often as once a minute if a clock is involved), but something else needs to display it on the large screen. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3649 |
It's quite a lot of extra effort, possibly a huge amount, to struggle to use a pico. So why? Especially when other ways are quite cheap & easy. John |
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