Composite vs DPI

Discussion about other hardware (including other Pi-like boards)
spongernz
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Composite vs DPI

Post by spongernz » Tue Sep 20, 2016 2:14 am

I've seen a lot of talk about GPIO based LCDs having a better picture than composite but haven't seen any example screen shots or videos. Is the GPIO solution still in the pipeline, hence my inability to find any comparison pics? Just would like to know how bad composite is before I start my build. The videos I have seen of composite doesn't look as bad as some people have described them. Any info or advice welcome.

spongernz
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Re: Composite vs DPI

Post by spongernz » Tue Sep 20, 2016 4:31 am

Thanks for the quick response kite. Just need a composite comparison pic now. Although I guess stills might not do the comparison justice?

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Re: Composite vs DPI

Post by Zero » Tue Sep 20, 2016 6:38 am

They do have better image quality in terms of sharpness of the image, but the refresh rate and therefore frames per second is nowhere near as smooth as composite. Most people choose smooth gameplay over better image quality. Stills won't show this of course. Using a gpio dpi screen is like having a Ferrari and driving it 10mph everywhere. Using a composite screen is like driving an average car at 60mph everywhere.

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kite
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Re: Composite vs DPI

Post by kite » Tue Sep 20, 2016 6:51 am

Zero wrote:They do have better image quality in terms of sharpness of the image, but the refresh rate and therefore frames per second is nowhere near as smooth as composite. Most people choose smooth gameplay over better image quality. Stills won't show this of course. Using a gpio dpi screen is like having a Ferrari and driving it 10mph everywhere. Using a composite screen is like driving an average car at 60mph everywhere.
Be very careful with your terminology.. you are talking about SPI.. DPI is NOT the same..
FYI those images above using DPI are at 125FPS which is over twice as fast as composite so infact the opposite of your statement is true ;) DPI > Composite > SPI

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Re: Composite vs DPI

Post by Zero » Tue Sep 20, 2016 8:19 am

I'm not saying that if someone has the in-depth knowledge to create their own drivers, etc, it isn't possible to get higher fps. But I've not seen any commercially available dpi lcds that would fit in a gameboy case with high fps and a nice sharp image. Would be good to get one if we can have the best of both worlds. Got some links to some good ones with drivers?

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Re: Composite vs DPI

Post by Zero » Tue Sep 20, 2016 9:19 am

Yes I think you're right as that's the only dpi lcd I've seen that works with decent fps, so you obviously know your stuff. Looks like you've done an impressive job. Have you thought about trying to use a small high-res mobile phone display?

DPI can be good but seems to require lots of effort and too much knowledge to reverse engineer something or to re-code proper drivers for most people, myself included. This was an interesting read (you probably know it all already but maybe something of interest):
http://blog.reasonablycorrect.com/raw-dpi-raspberry-pi/

I've been amazed at the lack of oled displays commercially available too (larger then postage stamp size). I know they cost more than older lcd's but would have thought some company would have pumped out a few by now with half decent specs for the general public.

Ahhh Bristol, hello neighbour :lol: ... I hate it here, seems I'm the only one though. :D

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Re: Composite vs DPI

Post by tinkerBOY » Sun Jul 23, 2017 8:59 pm

kite wrote:
Tue Sep 20, 2016 8:57 am
Zero wrote:I'm not saying that if someone has the in-depth knowledge to create their own drivers, etc, it isn't possible to get higher fps. But I've not seen any commercially available dpi lcds that would fit in a gameboy case with high fps and a nice sharp image. Would be good to get one if we can have the best of both worlds. Got some links to some good ones with drivers?
DPI LCD direct connectShow
DPI (parallel RGB) directly connected to Pi via large PCB:

Image

Here is the "driver" (note it won't exactly look like this or mount this way, it's just a prototype):

Image
I have used one for my board which will be ready soon (http://www.sudomod.com/forum/viewtopic.php?f=9&t=243), also I will release a driver board for standalone use too which will probably make this whole topic a lot more useful. I'm only here messaging because DPI was mentioned and I think I'm the only person to have done it so I'm claiming knowledge on the subject! :D If the subject was meant to be about SPI then I don't have examples (and yes they are slow and rubbish).

PS hello I live in Bristol too ;)
I was searching google for composite vs dpi comparisons and stumble upon this post. Does this mean that the image quality of those crappy 3.5" composite lcd screen can be improved via the DPI interface? Are the DPI LCDs different from the ones on composite LCDs? Forgive my ignorance.

Any update on the DPI driver board for stand alone use?
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Re: Composite vs DPI

Post by tinkerBOY » Sun Jul 23, 2017 9:01 pm

Zero wrote:
Tue Sep 20, 2016 9:19 am
Yes I think you're right as that's the only dpi lcd I've seen that works with decent fps, so you obviously know your stuff. Looks like you've done an impressive job. Have you thought about trying to use a small high-res mobile phone display?

DPI can be good but seems to require lots of effort and too much knowledge to reverse engineer something or to re-code proper drivers for most people, myself included. This was an interesting read (you probably know it all already but maybe something of interest):
http://blog.reasonablycorrect.com/raw-dpi-raspberry-pi/

I've been amazed at the lack of oled displays commercially available too (larger then postage stamp size). I know they cost more than older lcd's but would have thought some company would have pumped out a few by now with half decent specs for the general public.

Ahhh Bristol, hello neighbour :lol: ... I hate it here, seems I'm the only one though. :D
Great read! Thank you!
Game Boy Zero Controllers available @ tinkerBOY.xyz
tinkerBOY Controller v3.0 - built-in usb controller, usb audio, and usb hub
tinkerBOY Controller v2.0 - GPIO buttons and builtin PWM Audio and Amplifier
tinkerBOY Controller v1.1 - simple pcb button
* DPI Adapter - better display for GBZ
* keyboard converters - IBM XT/AT Soarer's Converter | ADB to USB Converter

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Re: Composite vs DPI

Post by moosepr » Mon Jul 24, 2017 1:57 am

the crappy composite screens are actually probably using DPI to talk to the screen, but the driver board (the bit you have to convert to 5v) is taking the composite signal and converting that to DPI (hence it not being brilliant). Composite screens dont use any GPIO, and dont need any special setup.

DPI is probably the best you can get as far as speed and quality goes. the only downside is that it uses pretty much all the GPIO pins, so they are not available to use elsewhere. DPI also needs some setting up, although i think its just some code in config.txt

SPI gets a bad writeup. It is not as fast as DPI, but you can still get a good quality screen as there is no 'conversion' going on. If you keep screen resolution to 240x320 or lower, things can actually run pretty well. There are some poor quality 3.5" screen that need 320x480 resolution, and have super slow connections that are worthy of the bad reputation.

my personal favourite is SPI because you get the crispness of DPI without using lots of GPIO, so you can use it for buttons. It was good enough for wermy to use in the MintyPi!! Have a look and see what you think

https://youtu.be/nE0DtXGXHAw
Get a small cheep LCD in your project https://www.sudomod.com/forum/viewtopic.php?f=22&t=2312
Wrap it all round a battery https://www.sudomod.com/forum/viewtopic.php?f=13&t=2292
Or use a custom PCB to make it really small https://www.sudomod.com/forum/viewtopic.php?f=13&t=2512
or make it really really really really tiny!! https://www.sudomod.com/forum/viewtopic.php?f=13&t=2919

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Re: Composite vs DPI

Post by tinkerBOY » Mon Jul 24, 2017 2:15 am

moosepr wrote:
Mon Jul 24, 2017 1:57 am
the crappy composite screens are actually probably using DPI to talk to the screen, but the driver board (the bit you have to convert to 5v) is taking the composite signal and converting that to DPI (hence it not being brilliant). Composite screens dont use any GPIO, and dont need any special setup.

DPI is probably the best you can get as far as speed and quality goes. the only downside is that it uses pretty much all the GPIO pins, so they are not available to use elsewhere. DPI also needs some setting up, although i think its just some code in config.txt

SPI gets a bad writeup. It is not as fast as DPI, but you can still get a good quality screen as there is no 'conversion' going on. If you keep screen resolution to 240x320 or lower, things can actually run pretty well. There are some poor quality 3.5" screen that need 320x480 resolution, and have super slow connections that are worthy of the bad reputation.

my personal favourite is SPI because you get the crispness of DPI without using lots of GPIO, so you can use it for buttons. It was good enough for wermy to use in the MintyPi!! Have a look and see what you think

https://youtu.be/nE0DtXGXHAw
Wow very nice video. Image quality on that screen looks great. Do you have a link to that screen you used? Is that 2.4"? I actualy have read some of your posts before on spi screens and been wanting to really try that. I guess im on a search for that perfect screen for gbz related projects.

I will definitely going to try the spi screen. Also will try DPI as well, so do you know any small screen that i can experiment with? I guess i can start with the crappy 3.5" screen that i already have?

Great insight, thank you!
Game Boy Zero Controllers available @ tinkerBOY.xyz
tinkerBOY Controller v3.0 - built-in usb controller, usb audio, and usb hub
tinkerBOY Controller v2.0 - GPIO buttons and builtin PWM Audio and Amplifier
tinkerBOY Controller v1.1 - simple pcb button
* DPI Adapter - better display for GBZ
* keyboard converters - IBM XT/AT Soarer's Converter | ADB to USB Converter

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