TFT Displays for P2 Eval
Rayman
Posts: 14,755
in Propeller 2
Think I'm about ready to offer this 4.3" display module (no touchscreen) for donation.
Connects directly to P2 Eval.
Uses the trick of octal D buffers to get 24-bit color using just 8 pins:
https://forums.parallax.com/discussion/169596/24-bit-color-on-4-3-tft-using-just-16-pins#latest
Basic driver is in pretty good shape:
https://www.youtube.com/shorts/VOVrhD1xqxo
Just noticed that Newhaven has a new IPS display that appears compatible. Ordered one just now to see...
https://newhavendisplay.com/4-3-inch-480x272px-ips-tft-without-touchscreen/
640 x 480 - 48K
Comments
Found an interesting transition guide for the Newhaven 4.3" LCDs:
https://newhavendisplay.com/content/docs/4.3IPS-TFT_TransitionGuide.pdf
Looks like they took care to make sure it's backwards compatible.
The ones I have are the generation before the old ones mentioned here.
But, they have the advantage of costing <$10.
New ones are >$43.
Still, the larger viewing angle and much more brightness might make it worth it.
New ones also come in a mountable version, that's nice:
https://newhavendisplay.com/tft-displays/?Size=4.3"__Diagonal&filterPage=1
Just noticed there are now 800x480 resolution versions that also look compatible and about the same price.
Looks very interesting 👍
Just realized I have a 5" 800x480 resolution Newhaven display on hand that is compatible with this hardware.
Unfortunately, there's just too many pixels for this to work without screen flicker.
However, could make a 16-bit color version using just one octal buffer chip.
Tested that out and at 250 MHz there's some flicker, but don't see any at 300 MHz.
But, I don't like having to have that high a clock...
Could skip the buffers and just do say straight 12 bits for color with maybe four bits each for green, red, and blue or something like that. Not terribly excited about this option either. Still, maybe 12 bits isn't all that bad?
Could be that 480x272 is about high as you can go with this kind of setup...
If these LCDs can be operated with CLK & DE only (can they?) I wonder if there is a way to derive DE from combined signal on a single pin? Maybe doing some type of voltage level adjust with the P2 DAC during the active period and use a fast comparator + monostable/counter circuit to generate DE when some level is exceeded. That could let you do 5:5:5 parallel RGB and one pin clock+DE using a dual P2-EVAL breakout solution. Or maybe you could drop another colour pin just output DE on a pin otherwise used for the LSB of one colour and get 16k colours instead of 32k.
In terms of raw bandwidth the P2 should easily be able to easily drive a 800x480 parallel LCD at 60Hz - I guess these latches slow it down quite a bit from there.
Another solution is to just steal a couple of extra pins from a third breakout header (an L shaped board fitted inside the P2 EVAL footprint solves that - I used that approach with a PSRAM board that needed 18 pins). Though it is wasteful if the remaining signals are not used and only really suits the P2-EVAL not the other boards that arrange the breakouts in a row (JonnyMac and KISS, P2 Edge small breakout etc).
There is a lot of HDMI LCDs which seems to be the simplest option: only 8 pins needed and 800x480 is not a problem for a P2
Yes, I think for WVGA, HDMI or EVE is better.
Yeah LCDs can certainly work at 800x480 nicely over DVI/HDMI with the P2. I think 1024x600 is a bit much though unless the LCD can be run with a slower refresh rate. I'm somewhat tempted to get a cheap Waveshare panel or clone to try it.
1024x600@50 Hz is doable at 336 MHz but with timings out of specifications (vsync and hsync way too short). I even tested this and it worked
but it may depend on a particular model of the display which has to accept this. kind of timings.
As I hoped, this board also works with the new Newhaven 4.3" IPS display (480x272).
It is noticeably brighter and the viewing angle is very much better.
Just posted Eagle schematic and 24 bpp driver demo here:
https://www.rayslogic.com/DonateForGear/P2Eval_4p3_NoTouch_Access.htm