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pzw

Which SPI TFT display controller?

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All,

 

I am looking for a 7 - 10" TFT display with SPI connection, and with touchscreen preferably via I2C, for a project of mine. I want to use the display to show just a static HTML page, without any window manager etc. Pretty basic principle I think. Looking at the website of www.buydisplay.com I see a few options with regards to the controllers used. 

The main options are:

- RA8875

- RA8876

- SSD1963

I can find online references to the RA8875 being supported by fbtft, but there is also a statement on the github page of fbtft that there will be no more development of fbtft ...

Before pulling the trigger on a display, I would really appreciate feedback which controller is supported by fbtft/armbian... :-)

 

Thanks for your time..

 

Paul

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44 minutes ago, pzw said:

7 - 10" TFT display with SPI connection

 

Resolution is your enemy, it will have to be a very chunky looking display or an extremely slow refresh rate.

 

@Larry Bank, you've more time invested in this arena, your thoughts?

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Refresh rate of 5 - 10 fps is enough for my application, as long as the update of the display seems seamless... :-)  The only reason for the refresh is to make the display not feel sluggish to touch...

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A refresh rate of 5-10fps through SPI is plausible for a 320x480 display, but at 800x480 it will be slower much slower.

 

The maximum I've been able to run SPI reliably is about 40Mhz, at that rate, your display refresh (at best) would be:

 

40,000,000 / (800 x 480 x 16) = 6.5fps. The reality is more likely that the SPI controller on those displays only runs reliably at up to 16Mhz and the inter-byte delays cause the refresh rate to be closer to 1-2 FPS. Very unpleasant to watch a screen update at that speed.

 

Is there a reason for avoiding HDMI or even composite video? Could you use a "sacrificial" $7 Orange Pi board to drive the display through HDMI and communicate with it over SPI?

 

P.S. Running FBTFT or some other kludge to get X11 output onto the display will add another level of headache.

 

P.P.S The touchscreen output is usually over SPI, not I2C.

 

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@Larry Bank

There is for me not a specific reason not to want to use HDMI... The big "problem" I have with the HDMI connection is the size of the connector...  I don't want to have a connector stick out on the side since I want to be able to build in the display in an enclosure not much larger than the display itself.

For me another option would be a display directly connected a MIPI-DSI port... But my oranges don't have it, and I do not want to use a RPi...

 

The application itself is very lightweight, so the sacrificial OPi would actually be the complete controller :-) ..

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4 hours ago, pzw said:

But my oranges don't have it, and I do not want to use a RPi...

 

Tinker Board has it, and it works on the Default images.  Might be a bit heavy-duty for your application though.

 

There are some FriendlyARM Elec setups with a smaller screen (4.3")

 

 

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