Home
JAQForum Ver 20.06
Log In or Join  
Active Topics
Local Time 09:24 26 Jun 2022 Privacy Policy
Jump to

Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.

Forum Index : Microcontroller and PC projects : Why VGA and not DVI/HDMI

     Page 2 of 3    
Author Message
matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 6225
Posted: 11:39am 30 Jan 2022
Copy link to clipboard 
Print this post

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
 
KD5ZXG
Regular Member

Joined: 21/01/2022
Location: United States
Posts: 53
Posted: 05:35pm 30 Jan 2022
Copy link to clipboard 
Print this post

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
 
Tinine
Guru

Joined: 30/03/2016
Location: United Kingdom
Posts: 1234
Posted: 06:35pm 30 Jan 2022
Copy link to clipboard 
Print this post

Hey Lewis, not knowing what kind of a budget you have for this but

There's this option.

Craig
 
Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 2443
Posted: 06:44pm 30 Jan 2022
Copy link to clipboard 
Print this post

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
 
Grogster

Admin Group

Joined: 31/12/2012
Location: New Zealand
Posts: 8107
Posted: 10:43pm 30 Jan 2022
Copy link to clipboard 
Print this post

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!
 
lew247

Guru

Joined: 23/12/2015
Location: United Kingdom
Posts: 1584
Posted: 04:10pm 31 Jan 2022
Copy link to clipboard 
Print this post

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


  Quote  This breakout board has no active components on it. It's just a connector you can plug an HDMI/DVI cable into, and 220 ohm series resistors. There's a spot for an I2C EEPROM and some resistors, but those are for advanced folks who may want to create a 'sink' device with an EDID. We don't place those parts on this breakout, since this is intended to be a 'source' only!

Wire it up to the bottom pins of your Pico board with the following:

   GP12 to D0+
   GP13 to D0-
   GP14 to CK+
   GP15 to CK-
   GP16 to D2+
   GP17 to D2-
   GP18 to D1+
   GP19 to D1-

And tie all the grounds together to one ground pin
 
Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 2443
Posted: 04:33pm 31 Jan 2022
Copy link to clipboard 
Print this post

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
 
lew247

Guru

Joined: 23/12/2015
Location: United Kingdom
Posts: 1584
Posted: 04:45pm 31 Jan 2022
Copy link to clipboard 
Print this post

  Mixtel90 said  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.


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
 
matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 6225
Posted: 05:08pm 31 Jan 2022
Copy link to clipboard 
Print this post

  Quote  I'm talking about doing the same as the VGA version does just with a higher res


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
 
JohnS
Guru

Joined: 18/11/2011
Location: United Kingdom
Posts: 2777
Posted: 07:04pm 31 Jan 2022
Copy link to clipboard 
Print this post

  lew247 said  just with a higher res

How?

Higher res = more bandwidth & more RAM.

Where are you getting them?

You may get them if/when a bigger Pico ships.

John
 
Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 2443
Posted: 07:28pm 31 Jan 2022
Copy link to clipboard 
Print this post

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
 
robert.rozee
Guru

Joined: 31/12/2012
Location: New Zealand
Posts: 1991
Posted: 08:30pm 31 Jan 2022
Copy link to clipboard 
Print this post

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
 
thwill

Guru

Joined: 16/09/2019
Location: United Kingdom
Posts: 2524
Posted: 10:39am 01 Feb 2022
Copy link to clipboard 
Print this post

  robert.rozee said  ... i expect will reach the point where it will do everything you are wanting.


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
CMM2 Welcome Tape, Creaky old text adventures
 
Mixtel90

Guru

Joined: 05/10/2019
Location: United Kingdom
Posts: 2443
Posted: 11:24am 01 Feb 2022
Copy link to clipboard 
Print this post

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
 
robert.rozee
Guru

Joined: 31/12/2012
Location: New Zealand
Posts: 1991
Posted: 11:55am 01 Feb 2022
Copy link to clipboard 
Print this post

  thwill said  ... I imagine that even with Peter's code for the PicRomite and (hopefully) MMB4W to cannibalize getting monitor display out of MMB4L is 12 months or more away ...


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
 
JohnS
Guru

Joined: 18/11/2011
Location: United Kingdom
Posts: 2777
Posted: 04:25pm 01 Feb 2022
Copy link to clipboard 
Print this post

I suspect I don't - I've never had reason to do it.

Sorry.

John
 
thwill

Guru

Joined: 16/09/2019
Location: United Kingdom
Posts: 2524
Posted: 04:33pm 01 Feb 2022
Copy link to clipboard 
Print this post

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
CMM2 Welcome Tape, Creaky old text adventures
 
Tinine
Guru

Joined: 30/03/2016
Location: United Kingdom
Posts: 1234
Posted: 08:23pm 01 Feb 2022
Copy link to clipboard 
Print this post

  Mixtel90 said  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.


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
 
lizby
Guru

Joined: 17/05/2016
Location: United States
Posts: 2092
Posted: 08:43pm 01 Feb 2022
Copy link to clipboard 
Print this post

  Mixtel90 said  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.

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.
 
JohnS
Guru

Joined: 18/11/2011
Location: United Kingdom
Posts: 2777
Posted: 10:01pm 01 Feb 2022
Copy link to clipboard 
Print this post

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
 
     Page 2 of 3    
Print this page
© JAQ Software 2022