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I successfully installed KeDei 3.5 inch 480x320 TFT LCD on a Raspberry Pi Zero with Raspbian Buster. It works nicely as text console, especially when I use lens to magnify the view. :-)

However, I want to use it for another purpose: I would like to keep the regular screen & console output at HDMI port and use the LCD as a special-purpose peripheral.

Is there any tutorial how to set up this kind of device (TFT LCD with SPI interface) either as a serial port, or some other kind of device that would allow it to be used by a single application for special prupose, such as control panel for some communication equipment?

Or should it be sufficient to learn about KeDei's LCD protocol and write communication routines accordingly?

Thank you

P.S. Did anybody try this yet?

Jindrich Vavruska
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  • Hi @Jindrich Vavruska, Never heard of KeDei. Can you give us a link? – tlfong01 Sep 28 '19 at 12:07
  • http://kedei.net/raspberry/raspberry.html (page with driver download), https://www.ebay.com/itm/3-5-3-5-Inch-TFT-LCD-Touch-Screen-320x480-SPI-RGB-Display-for-Raspberry-Pi-B-B/201449704007?hash=item2ee7568a47:g:oXgAAOSw9NdXqtkl (newer HW version, but from the same source) – Jindrich Vavruska Sep 28 '19 at 12:35
  • Thank you for your info. I quickly googled and found that your KeDei seems to be using ILI9341 – tlfong01 Sep 28 '19 at 13:14
  • Your Kedei touch screen seems to be using ILI9341 which I played with a couple of months ago: LCD TFT screen 2.8" ILI9341 SPI connect https://raspberrypi.stackexchange.com/questions/98549/lcd-tft-screen-2-8-ili9341-spi-connect. I forgot the details. I need to google to refresh my memory. – tlfong01 Sep 28 '19 at 13:17
  • More links: (1) Raspberry Pi SPI 3.5" TFT TouchScreen - 2015aug27 http://heikki.virekunnas.fi/2015/raspberry-pi-tft/ (2) KeDei LCD https://kedei.world.taobao.com/ (3) Rpi3B+ 60Hz TouchScreen 3.5" LCDTFT - ¥39 https://item.taobao.com/item.htm?spm=a312a.7700824.w4004-9718302419.9.7f4c2befks1WBO&id=574180372545.
    (4) Rpi 7"/5" LCD Touch Screen usb - ¥156 https://item.taobao.com/item.htm?spm=a312a.7700824.w4004-9718302419.3.7f4c2befks1WBO&id=588962806803. My first impression is that KeDei is a reputable vendor. So it is a good idea to invest time on its products.     – tlfong01 Sep 28 '19 at 13:20
  • Since KeDei provides drivers for Rpi, though might not be Rpi4B. But I guess if you use Rpi3B+ (like I did in my post), you don't need to build a kernel, just use the kernel provided by the vendere KeDei. I stalled my test because I was waiting for Rpi4B. Now I have Rpi4B, perhaps it is time to resume my tests. You might like to read the links I gave above and confirm my guess is correct. – tlfong01 Sep 28 '19 at 13:25
  • @tflong01 Well, in fact I do not want to use their custom-built kernel. As soon as I used it, some other hardware stopped working. Back to the original topic, I am not very experienced in this kind of system programming. I am looking for something of the sort of "second screen" (independent device from HDMI) and in this screen having a tty device able to provide full-screen display in ncurses, or in HTML view, and providing events from the touch panel on the LCD. So that the system console runs independently fdrom the LCD screen (and could be displayed on HDMI if connected). – Jindrich Vavruska Sep 28 '19 at 14:28
  • Yes, I agree you don't need to build your own kernel, just use the one given by the vendor (which I visited their website and found them OK, not any rubbish ODM). And I do wish what you want, one big HDMI screen, another small LCD touch screen, text and graphics. My Micky Mouse projects are mostly away from the desk, so in real use, I don't need the big HDMI, which is useful only for development. Anyway, bed time for me. Good luck and see you tomorrow. – tlfong01 Sep 28 '19 at 14:50

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