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

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Mixtel90

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Joined: 05/10/2019
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Posted: 10:33pm 01 Feb 2022
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I don't think Lewis realised *why* the PicoMite is VGA. I suspect he saw it as an old-fashioned system now, when even DVI is long in the tooth. After all, HDMI *seems* so simple now and it's supported by everything, including SBCs like the other RPi boards. I can't blame him if this is how he felt.

It's just unfortunate that, great though it is, the current version of the RP2040 isn't ideal for generating video (and I don't think it was something the designers even considered at the time, after all, you wouldn't expect video generation from a small Arduino, would you?). It's taken a CPU core and one of the PIOs together with a fair percentage of precious RAM to get VGA at the resolutions we do have. It's possible to get things like higher resolution, but not if you want to do anything else useful as the RAM isn't all that big to start off with.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs
 
JohnS
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Joined: 18/11/2011
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Posted: 10:47pm 01 Feb 2022
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OK, so thread closed LOL

John
 
lew247

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Joined: 23/12/2015
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Posted: 08:28am 02 Feb 2022
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  JohnS said  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

Because I can't program in any other language, I struggle with MMBasic as it is.
I just thought because it can be done in Python then it should be possible to display images in basic?

  Mixtel90 said  I don't think Lewis realised *why* the PicoMite is VGA.

True
  Mixtel90 said  It's just unfortunate that, great though it is, the current version of the RP2040 isn't ideal for generating video

Video was never even thought of, it was IMAGES at higher than 320x240 pixels in the colour mode
 
Mixtel90

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Posted: 11:19am 02 Feb 2022
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The trouble is always that you need a frame buffer:
(number_of_x_pixels * number_of_y_pixels)/8 * (red_colour_depth + green_colour_depth + blue_colour_depth)
as a bare minimum. :)

That number adds up rapidly. It doesn't matter whether it's stationary images or video as video is only a series of stationary images that are slightly different. It doesn't change the size of the frame buffer needed, only how fast you have to update it.

You have to make any updates to the frame buffer at the end of each displayed frame and it has to be ready for the start of the next (you can't change anything during a frame output or you get flicker). As the frames start every 1/50th (or every 1/60th) of a second and you have to complete the process between the end of one frame and the start of the next you don't really have a lot of time.

Current 16-colour VGA mode: (320 * 240)/8 * 4 = 38400 bytes = 37.5kB
Current mono VGA mode: (640 * 480)/8 * 1 = 38400 bytes = 37.5kB

640x480 16 colours: (640 * 480)/8 * 4 = 153600 bytes = 150kB
800x600 16 colours: (800 * 600)/8 *4 = 240000 bytes = 234.4kB
720P 16 colours: (1280 * 720)/8 * 4 =  460800 bytes = 450kB

... as I said - these numbers add up rapidly. :(
The CMM2 has far more RAM available for the frame buffer so it can have higher screen resolutions and colour depths than the PicoMite.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs
 
JohnS
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Joined: 18/11/2011
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Posted: 12:41pm 02 Feb 2022
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  lew247 said  
  JohnS said  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

Because I can't program in any other language, I struggle with MMBasic as it is.

OK, so why not use one of the other devices that run MMBasic?

John
 
lew247

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Joined: 23/12/2015
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Posted: 01:17pm 02 Feb 2022
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  JohnS said  
OK, so why not use one of the other devices that run MMBasic?
John

What other device is there than has higher resolution than 320x240 in colour other than the CMM2?
I'm not going to spend hundreds on a console I'll never use again for anything else

Anyway as the original question has been answered I guess the only thing I can do is give up on the thought
 
thwill

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Joined: 16/09/2019
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Posted: 01:52pm 02 Feb 2022
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Time to (try and) put this one to bed.

Within 12 months I would hope we have two MMBasic ports in addition to the CMM2 that can do hi-res graphics:

1. MMBasic for Windows (is it officially MMB4W?)
2. MMB4L - which will run on a Pi Zero and time and enthusiasm permitting your Android Phone, ChromeOS tablet and whatever MacOS is called in 12 months.

Of course there is the danger we will also have:

3. MMBasic for Windows for Linux (MMB4W4L)
4. MMB4L for Windows (MMB4L4W)

But as I've said before TBS is not a company, and Peter and I are working to very different time-scales, and even if we weren't I'm not sure we were made for close collaboration when it comes to hobby projects - and just to be clear I think he's great (you're all great) and don't have any argument if anyone thinks I'm the problem .

Best wishes,

Tom
Edited 2022-02-03 00:13 by thwill
CMM2 Welcome Tape, Creaky old text adventures
 
Mixtel90

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Joined: 05/10/2019
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Posted: 02:23pm 02 Feb 2022
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It's a pity that the PicoMite is the easiest MMBasic device to get hold of at the moment. I see that WhiteWizard is out of stock of all the CMM2 series according to his web site.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs
 
JohnS
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Joined: 18/11/2011
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Posted: 02:46pm 04 Feb 2022
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Is a whole CMM2 needed, isn't just the waveshare board enough?

(Maybe even a NUCLEO H743 with some tweaks)

John
 
Amnesie
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Joined: 30/06/2020
Location: Germany
Posts: 193
Posted: 03:33pm 04 Feb 2022
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I ordered the gerbers for the CMM2 and built the whole thing, it was a pain in the a** to get all the things in Germany, shipping costs etc.

So I really see the future in the following versions:

Windows / Linux Version and the PicoMite It is really simple: What is the point of a device which is great, but nobody can afford or built because you wont get the parts? As I said, I built the original maximite and the CMM2 as well as the PicoMite.

The PicoMite costs: 3,90euro RaspberryPico + SD Breaktout 3euro + RTC 1 euro + LCD ~ 10 euro, so 17,90 Euro in total (this is insane)! With all the shipping costs and parts my CMM2 was around 130 Euro! Not to mention the time to source all parts (up to 2 months)...

P.S.: in the end I fried a ADC pin of the CMM2 and the whole Waveshare board was
useless for me... With the RaspberryPi Pico I just have to spend 3,90 Euro...

Greetings
Daniel
Edited 2022-02-05 01:51 by Amnesie
 
Volhout
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Joined: 05/03/2018
Location: Netherlands
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Posted: 03:59pm 04 Feb 2022
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Amnesie,

You are comparing apples to pears.
The CMM2 is a completely differen machine from the pico. It is more powerfull, has far more IO, but also...it is a system. The pico cannot do anything without a PC. (unless you build the VGA picomite, which is more like CMM1 with fewer IO pins, but better basic).

Although I mentioned I was not waiting for a VGA picomite (I have a CMM1), I will build one anyway, because of it's better basic. However I still have to find a PS2 keyboard (my CMM1 is build INTO that last PS2 keyboard I had, like an 80's home computer).
In that aspect I have to agree with Robert, support for a USB keyboard on the VGA picomite would definitely be a pro.

The pico is (for some reason) not affected by the chip shortage. Maybe becuase when this chip shortage started it was not designed in in a car or kitchen appliance yet (too new) and the STM32 series is used in existing products. So the industry bought every single device they could lay their hands on, and the hobby circuit suffers.

Volhout
If nothing goes right ... turn left
 
Mixtel90

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Posted: 04:56pm 04 Feb 2022
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I suspect the RP2040 is not only a very cheap chip to make, but Raspberry Pi ordered a serious amount of them, possibly on some sort of scheduled order. At any rate, they are able to sell them by the reel now if you are interested. :)

I don't know the cost and availability of the Waveshare module now, but I bought a pcb on ebay as it worked out about the same as getting 5 made and leaving 4 to rot. lol Likewise, I managed to get quite a few of the other bits on ebay. Just a few had to come from RS and Farnell. The case was awkward to source. Eventually it all cost a little more than it would have if I'd bought it from Micromite.org.

I had very little problem in finding PS/2 keyboards on ebay. You have to think of the expected life of things. If PS/2 keyboards are likely to be available for, say, another five years then that's possibly going to be after the PicoMite is superseded. In that case there's little point in changing the current PicoMite to use a USB keyboard. It might be interesting, but it's not a necessity yet.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs
 
Amnesie
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Joined: 30/06/2020
Location: Germany
Posts: 193
Posted: 08:21pm 04 Feb 2022
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  Volhout said  Amnesie,

You are comparing apples to pears.
The CMM2 is a completely differen machine from the pico. It is more powerfull, has far more IO, but also...it is a system. The pico cannot do anything without a PC. (unless you build the VGA picomite Volhout


There is always some benifits or a trade off if you compare them, but I designed my PicoMite PCB as a system like the CMM2 and the VGA version is a system, too. They are able to do the same things but for way cheaper price and better availability! In my opinion the best system (for example CMM2) is useless if you don't get the parts easy (even pre Corona). This is exactly my case since I burned my Waveshareboard and I am not willing to pay again around 30 euro only for the board.

  Volhout said  
However I still have to find a PS2 keyboard (...)support for a USB keyboard on the VGA picomite would definitely be a pro.Volhout


I have not a single pure USB keyboard! All of them have a USB connector, but they all support the PS/2 protocol AND USB protcol. I have six different mechanical keyboards by "Cherry", due to a lot of Arduino programming I am used to PS/2 protcol, I see no need for USB. Have you tried your "USB" keyboard with a PS/2 adaptor? Maybe your keyboard supports this protocol too? Many support both protocols.

Greetings
Daniel
Edited 2022-02-05 06:40 by Amnesie
 
JohnS
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Joined: 18/11/2011
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Posts: 2765
Posted: 09:14pm 04 Feb 2022
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  Amnesie said  The PicoMite costs: 3,90euro RaspberryPico + SD Breaktout 3euro + RTC 1 euro + LCD ~ 10 euro, so 17,90 Euro in total (this is insane)! With all the shipping costs and parts my CMM2 was around 130 Euro! Not to mention the time to source all parts (up to 2 months)...

P.S.: in the end I fried a ADC pin of the CMM2 and the whole Waveshare board was
useless for me... With the RaspberryPi Pico I just have to spend 3,90 Euro...

Greetings
Daniel

All very well but how is it helping with the subjects of the thread?

John
Edited 2022-02-05 07:15 by JohnS
 
lizby
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Joined: 17/05/2016
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Posts: 1997
Posted: 09:23pm 04 Feb 2022
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  Amnesie said  I designed my PicoMite PCB as a system like the CMM2 and the VGA version is a system, too. They are able to do the same things . . .


Not quite--you are not going to run Mauro's Final Fight or Gauntlet or Wolfstein (see here ) on the Picomite, but in general, I agree--Peter's latest changes allow the PicoMite to be a stand-alone Basic language system, with keyboard and editor and most of the MMBasic goodies, and the price for that combination is unbeatable.
 
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