Simple instructions (assuming a new Raspbian install) to install Kuman 3.5 TFT LCD on Raspberry Pi 3 Model B.
a. Download Rasbian strech (with desktop) and extract the .img file from the downloaded zip (it’s always good to also check the hash of the downloaded file)
b. Insert the SD card and make note of the device being used (make sure you get this right not to overwrite your OS)
c. Use dd to copy the image to the SD card (the values for if and of should be changed accordingly. If you never used dd please do yourself a favor and read up first)
sudo dd bs=4M if=2018-04-18-raspbian-stretch.img of=/dev/mmcblk0 status=progress oflag=sync
d. Once the process is done, mount (if needed) the boot and rootfs partitions
e. Browse to the mount point of boot and create a blank file called ssh (to enable sshd on boot)
touch ssh
f. Open cmdline.txt and write down the value of root=. Now substitute the existing line with the line below, and then change the value of root= back to the original value
dwc_otg.lpm_enable=0 console=tty1 console=ttyAMA0,115200 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait fbcon=map:10 fbcon=font:ProFont6x11 logo.nologo
g. Open config.txt and add the lines below to the end of the file
dtparam=audio=on
dtparam=spi=on
dtoverlay=ads7846,penirq=25,penirq_pull=2,xohms=150,swapxy=1,xmin=300,ymin=700,xmax=3800,ymax=3400,pmax=255
dtoverlay=waveshare35a
h. Download waveshare35a-overlay.dtb from GitHub to /boot/overlays and rename it to waveshare35a.dtbo
i. Change Option "fbdev" "/dev/fb0" in /usr/share/X11/xorg.conf.d/99-fbturbo.conf to Option "fbdev" "/dev/fb1"
Section "Device"
Identifier "Allwinner A10/A13 FBDEV"
Driver "fbturbo"
Option "fbdev" "/dev/fb1"
Option "SwapbuffersWait" "true"
EndSection
j. Create a new file /etc/X11/xorg.conf.d/99-calibration.conf with the lines below
Section "InputClass"
Identifier "calibration"
MatchProduct "ADS7846 Touchscreen"
Option "Calibration" "3932 300 294 3801"
Option "SwapAxes" "1"
EndSection
k. Reboot and enjoy
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