Posts: 8
Joined: Wed May 15, 2019 10:05 pm

Joy-it 7" touchscreen, gt811 not supported by default

Mon May 20, 2019 10:54 pm

Joy-it 7 inch display, which looks quite similar to Waveshare...
Someone owning Waveshare screen, plz inform if it has gt811
too 8-)

Local dealer was selling these and I purchased one, because
unlike the official 7" screen, this doesn't use dsi-port, and my
Raspberry Zero W doesn't have one. This screen needs HDMI
and USB both connected to Raspberry.

In addition to that, some configuration.
Basic configuration is done by a script available:
git clone https://github.com/goodtft/LCD-show.git
LCD7C-show is the one for this display,, it is a shell script
so you can view it and see what it actually does.

With this configuration the screen works just like a pc monitor
would do. No touchscreen functionality though. It doesn't respond
at all.

After replacing the screen thinking it is faulty, I got a new one,
and after fiddling with the configurations with a little help from
pdf-file provided by Joy-it, I had done everything there is to
configure. My Raspberry doesn't even react when the usb
is disconnected and reconnected. I even purchased Rpi 3b+,
because my Zero W wasn't listed in the supported models.
But that was not the problem.

None of the instructions told, that gt811_ts -kernelmodule is
needed. It doesn't seem to be in the raspbian kernel, nor
linux vanilla kernel. Google reveals that there is old chinese
distribution sunxi-linux, which was made for tablets back
in 2010. The code is terrible, is has includes from outside
of the kernel source, and quite a lot references to other
kernel modules not present in my raspbian kernel sources.
So i took roughly 48 hours to get it compiled, but it never
made through modpost checks. Then I found some better
code... <https://www.cnblogs.com/zym0805/p/4413351.html>

This compiles without a problem with current raspbian
kernel source, and now the touchscreen functionality is
working too. The kernel module doesn't load up automatically,
it has to be manually added.


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