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Good small display recommendations anyone?

Posted: Tue Mar 26, 2019 12:57 am
by Poi
Does any one have any recommendation for a fast and small display (between 3 and 5 inches) to use with a Pi Zero?

I'm looking into getting a new screen because just yesterday I realised that the display I got, an Adafruit 3.5' TFT, might not be the best fit for game development. Everything had been going well so far with Ultibo and I must say that Free Pascal isn't as a terrible as I thought, infact it's pretty cool, but as soon as I tried to do a basic game loop, I slowly started to realise why is it that a lot of people say you shouldn't bother with these SPI displays.

I found out that it doesn't support vsync, which makes the loop a bit janky and it doesn't support virtual dimentions either, so there goes the back buffering technique. But mainly it seems that the refresh rate is just too slow, specially if you want to update the whole screen continuously. It looks like I need to slow down the update loop to about 4 - 7 FPS before I can stop seeing weird artifacts. That is no good.

Re: Good small display recommendations anyone?

Posted: Tue Mar 26, 2019 2:49 am
by Gavinmc42
Manga screen 2, full HD HDMI 1920x1080 5.9", on my Santa list ;)
If you can afford using up the GPIO, Hyperpixel 4.0"
For a Zero the Adafruit 240x240 IPS 1.54"

Any others look at the driver chips to make sure they are supported.
core/fpc/3.1.1/source/rtl/ultibo/drivers
hx8357d, ili9340 etc

SPI ones will be slow, some have said more than 320x240 is too many pixels to move around.
There are tricks like only writing the changed pixels.
Clues in the Linux fbtft drivers etc.

Wish we had mose options for LCDs, DSI ones? IPS screens and OLEDs.
But they are a bit like camera sensors, need to buy lots before maunfacturers will talk to you.
Still it is much better now than 10-20 years ago.

I hope we see more displays like the Manga screen 2.
FHD in 5 to 9" :D

Re: Good small display recommendations anyone?

Posted: Tue Mar 26, 2019 7:57 am
by hansotten
If you need fast screen updates only VC4 driven video screens will do. This means HDMI, DSI (not on the RPi Zero, the official 7 inch only), DPI (e.g. Hyperpixel, Kippah and VGA666), composite.
SPI is a PITA, driver problems, slower and most with a low price quality just above composite.

Plenty of 800x480 LCD HDMI touch 5 inch based screens on Aliexpress. About $25. Expect acceptable quality. Awkward extruding placement of connectors
Composite small LCD screen are even cheaper, but are lower quality.
HDMI and Composite are easy to use with Ultibo with just config.txt settings.

Hyperpixel is high quality, takes nearly all GPIO, is more expensive, and fits very nicely without extruding connectors. Needs a bit of extra Ultibo work (there is a topic about it).
The DPI based Kippah from Adafruit is even more expensive.

Re: Good small display recommendations anyone?

Posted: Wed Mar 27, 2019 12:03 am
by Poi
Thanks for the info, I think I'll stick to HDMI then, the HyperPixel does look cool, but I was hoping to use some GPIO pins.

Do you guys think this will work with Ultibo?

https://www.waveshare.com/4inch-hdmi-lcd.htm

It connects to the Pi using a 26 pin header, but it should work with a 40 pin header aswell, right?

Re: Good small display recommendations anyone?

Posted: Wed Mar 27, 2019 12:43 am
by Ultibo
Poi wrote:Do you guys think this will work with Ultibo?

https://www.waveshare.com/4inch-hdmi-lcd.htm

Are you planning to use the touchscreen?

Re: Good small display recommendations anyone?

Posted: Wed Mar 27, 2019 12:48 am
by Gavinmc42
That should work, plenty of people are using Waveshare displays now.
I must have missed those HDMI versions, will add them to my Santa list.

HDMI will be easier to get working too.
The touch screen part needs the GPIO connector, probably SPI based chip?
Whoops scroll down, read data, definitely SPI.

Wow 5.5" 1920x1080 AMOLED I want. So many IPS displays too.
Waveshare seems to have gone from a few ripped off Adafruit LCDs to a market leader?

The touch screen is going to be the issue, you might end up on your own trying to figure it out in Ultibo.
Probably just a matter of converting Linux C code to Free Pascal?
Wonder who sell them around here?

Re: Good small display recommendations anyone?

Posted: Wed Mar 27, 2019 12:59 am
by Poi
Actually I am not interested in the touch functionality at all, but it seems all of this types of displays support it. It's more difficult to find something without a touch screen.

I must be getting old, but touch will never beat a button press, like ever not in a million years :P

Re: Good small display recommendations anyone?

Posted: Wed Mar 27, 2019 1:05 am
by Ultibo
Poi wrote:Actually I am not interested in the touch functionality at all, but it seems all of this types of displays support it. It's more difficult to find something without a touch screen.

Then the HDMI display part should work fine with Ultibo, you'll just need to apply the correct config.txt settings from the Waveshare documentation.

The only other thing you might need is to figure out from the device tree overlays how to control the backlight (possibly uses a GPIO).

Re: Good small display recommendations anyone?

Posted: Wed Mar 27, 2019 1:19 am
by Gavinmc42
I must be getting old, but touch will never beat a button press, like ever not in a million years

Me too, after a 2 week wait a bunch of hall effect sensors showed up.
Tested first one with one of my collection of tiny magnets, worked great - hall effect keyboard now in design :D
Buckling spring and hall effect :D

The touch overlay on LCDs also effects screen visibility, wonder if Waveshare have versions without touch?
SPI on Ultibo may be easier than USB touch, not sure how those USB ones work, could be just USB HID mouse protocol.
Wonder if I can convince Santa to come early?

Re: Good small display recommendations anyone?

Posted: Wed Mar 27, 2019 8:39 am
by hansotten
Poi wrote:Thanks for the info, I think I'll stick to HDMI then, the HyperPixel does look cool, but I was hoping to use some GPIO pins.

Do you guys think this will work with Ultibo?

https://www.waveshare.com/4inch-hdmi-lcd.htm

It connects to the Pi using a 26 pin header, but it should work with a 40 pin header aswell, right?


It will work fine. But it does block the GPIO connector and reserves SPI. And not as cheap as the generic 5 inch HDMI LCD screens. The backlight control is just a switch on/off you can solder on, not GPIO controlled.