Would an Arduino screen be compatible with pi? Example pic inside

Arduino-related hardware discussion (including Teensy and other Arduino clones)
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tronicgr
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Re: Would an Arduino screen be compatible with pi? Example pic inside

Post by tronicgr » Thu Jul 07, 2016 8:56 am

Well, I know it's not perfect, but for SPI screen is impressive fast.

I like HDMI quality better as well, thus I made an HDMI version portable console as well:

https://youtu.be/Z1nhiFUIgjA
https://youtu.be/k_8VuSDbD9E

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Thanos

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Re: Would an Arduino screen be compatible with pi? Example pic inside

Post by chiz » Thu Jul 07, 2016 9:16 am

wermy wrote:
tronicgr wrote: Actually the ili9341 based screens are all capable of 60hz refresh rates. I made a PiGrrl2 with a 2.8inch and a PiGrrl Zero with a 2.2inch screens that are very clear and have fast refresh rate:

https://youtu.be/-KWqAKD5TM0
https://youtu.be/ct3Clmvc-KQ

Of course you can use cheap $6 ili9341 displays instead of using the ones from adafruit, I tried some of these and work the same.

Oh, and another thing, the power consumption on these screens can be around 70mA to 100mA only so makes them useful for battery operated projects. I measured as low as 170mA for both raspberry pi zero and an 2.2inch ili9341 screen when in idle state, and 250mA when running neogeo metalslug.

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Thanos
Hm, are you sure it's actually refreshing at 60fps? I could never get it to refresh as smoothly or quickly as an HDMI or composite display. In your builds in the videos (which look great btw!) you can see the screen refreshing in a weird diagonal refresh pattern when it tries to update the entire screen at once (when the emulationstation splash screen disappears, when loading up a new game, etc). That's the same sort of behavior I was seeing. This effect is a little harder to see once you're in-game, but it illustrates that it definitely does not refresh as fast as a normal screen. Additionally there is some definite lag to the screen (so when you push jump or whatever it doesn't happen instantaneously like it does when you plug in an HDMI screen).

Anyway, glad you got it working to your liking but those little things turned me off of using those screens in these types of projects. :)
@wermy
There's a command or api that lets you set the FPS to a higher value from the default. I just cnt find the link. As @tronicgr said, he and others were able to pump videos at 60fps.

Regarding a controller board. If I'm not mistaken, @kite's board will also be driving the lcd through the Pi's GPIOs which is done through SPI. Without the board, one can still directly connect the lcd pins to the Pi. Kite's board will make it easier for everyone.

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Re: Would an Arduino screen be compatible with pi? Example pic inside

Post by wermy » Thu Jul 07, 2016 9:34 am

chiz wrote: @wermy
There's a command or api that lets you set the FPS to a higher value from the default. I just cnt find the link. As @tronicgr said, he and others were able to pump videos at 60fps.

Regarding a controller board. If I'm not mistaken, @kite's board will also be driving the lcd through the Pi's GPIOs which is done through SPI. Without the board, one can still directly connect the lcd pins to the Pi. Kite's board will make it easier for everyone.
Well, if it is possible to get it running as smoothly and lag-free as a composite or HDMI screen I'd love to see how. A PiTFT from Adafruit was actually the first screen I tried for a project like this (followed by a different SPI display after I gave up on the Adafruit one), but even following their guide ( https://learn.adafruit.com/running-open ... t-displays ) I could not get it (or the other one) to work to my liking. ¯\_(ツ)_/¯
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Re: Would an Arduino screen be compatible with pi? Example pic inside

Post by kite » Thu Jul 07, 2016 9:47 am

chiz wrote:...
Regarding a controller board. If I'm not mistaken, @kite's board will also be driving the lcd through the Pi's GPIOs which is done through SPI. Without the board, one can still directly connect the lcd pins to the Pi. Kite's board will make it easier for everyone.
Just to correct you, but my board does NOT use SPI, it uses DPI (or Parallel RGB) and it is not a generic purpose data bus (so no two way, basically it's not SPI..). SPI requires the Pi in software to capture the buffer, and push it into the SPI output/buffer.. DPI comes DIRECT from the GPU, so there is no software 'running in the background' like with SPI.. think of it as the VGA port on your graphics card on a normal PC, it is just another output.. whereas the SPI TFT's are the equivalent of a USB webcam, which require an app running to use it (unlike the VGA port which works all the time, driver or no driver, but the webcam won't work without the driver, and when in use increases CPU load..).

People have probably got 60FPS by doing clever things such as only sending pixel data for changed pixels.. however if the entire screen changes at once you will see visible tearing/lag.. This is not the case for DPI as it sends the complete frame every time, and for mine at 125FPS. Just want to make it clear the difference and for why the SPI screens are not worth bothering with, unless you want slow static images (think picture frame, or weather station GUI). You can get small DPI enabled screens for ultra cheap, I'm working on making the adapter for a 2.6" screen :)

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Re: Would an Arduino screen be compatible with pi? Example pic inside

Post by chiz » Thu Jul 07, 2016 10:54 am

@kite
I stand corrected. :) thanks for the insight. Obviously my research isn't enough yet as I didnt know about DPI. (I only know about dots per inch but that's diff. :))

Anyways, as you said, I should go with DPI and not SPI. Can you direct me to where I can buy a cheap 2.8" DPI screen and documentation on how I can drive it using the RPi? Im looking for something similar for my next build as I'm unable to find any 2.8" composite video LCDs.

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Re: Would an Arduino screen be compatible with pi? Example pic inside

Post by kite » Thu Jul 07, 2016 11:32 am

chiz wrote:...
Can you direct me to where I can buy a cheap 2.8" DPI screen and documentation on how I can drive it using the RPi? Im looking for something similar for my next build as I'm unable to find any 2.8" composite video LCDs.
Read through my build log I do detail all the bits there and should have some information on how to find the screens, when I have something working I'll post links. All of them require a custom pcb to interface with the pi unless you want to solder 28tiny wires to a 0.5mm pitch FPC cable ;)

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Re: Would an Arduino screen be compatible with pi? Example pic inside

Post by chiz » Thu Jul 07, 2016 2:18 pm

@Kite
Thinking of using an FPC adapter such as this. Planning on tinkering until you can have your display board go live. ;)

I too think that DPI will allow us to expand our choice of screen sizes which in turn would pave the way to more types of custom projects of diff shape and sizes.

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