If you messed with /boot/config.txt or /etc/rc.local you may have removed or disabled some of the elements required for the PiTFT to work. Try re-running the Easy Installer script!

The Raspberry Pi 4 and the Raspberry Pi 400 have dual HDMI outputs. However, only one of those is a primary port. The is likely caused by connecting to HDMI1. Please try connecting the display to the other HDMI port and rebooting.

For the Pi 4, HDMI 0 is closer to the USB-C port. For the Pi 400, it's the port closer to the MicroSD Card slot.

Sounds like you tried to configure your Pi to 'boot straight to X', that is, start up the graphics interface on boot. This doesn't work by default because the Pi operating system is not expecting a PiTFT so it boots to the HDMI output. See below for how to set up your Pi to boot to X on the PiTFT

To 'fix' this, you can either connect an HDMI monitor, then in a terminal window run sudo raspi-config and configure the Pi to boot to the command line not X! If you do not have an HDMI monitor, you can also try a console cable

Some programs are graphics-optimized, particularly the video playback tools and some other programs like Minecraft. They write 'directly' to the HDMI output, and cannot write to the PiTFT so there is no way to directly make them work. However, you can have the output go to HDMI and then mirror the HDMI onto the PiTFT with fbcp. Using the Easy Installer, select Mirror HDMI

You can change the SPI frequency (overclock the display) by editing /boot/config.txt and changing the dtoverlay options line to:

dtoverlay=pitft28r,rotate=90,speed=62000000,fps=25

Or whatever you like for speed, rotation, and frames-per-second. BUT, here's the thing, the Pi only supports a fixed number of SPI frequencies. So tweaking the number a little won't do anything. The kernel will round the number to the closest value. You will always get frequencies that are 250MHz divided by an even number. Here's the only SPI frequencies this kernel supports

• 15,625,000 (a.k.a 16000000 = 16 MHz)
• 17,857,142 (a.k.a. 18000000 = 18 MHz)
• 20,833,333 (a.k.a 21000000 = 21 MHz)
• 25,000,000 (= 25 MHz)
• 31,250,000 (a.k.a 32000000 = 32MHz)
• 41,666,666 (a.k.a 42000000 = 42MHz)
• 62,500,000 (a.k.a 62000000 = 62MHz)

So if you put in 48000000 for the speed, you won't actually get 48MHz, you'll actually only get about 42MHz because it gets rounded down. We tested this display nicely with 32MHz and we suggest that. But you can put in 42MHz or even try 62MHz and it will update faster

You can tweak fps (frames per second) from 20 to 60 and frequency up to 62MHz for tradeoffs in performance and speed. Reboot after each edit to make sure the settings are loaded properly. There's a trade off that if you ask for higher FPS you're going to load the kernel more because it's trying to keep the display updated.

Make sure your Pi boots to the graphical PIXEL desktop on the HDMI output monitor, then using the Easy Installer, select Mirror HDMI

This happens on the Raspberry Pi the first time you run startx, no matter what display. You can just re-start X and it wont appear again.

Yes!  Please see this post:

https://forums.adafruit.com/viewtopic.php?f=47&t=77528&p=393280#p393322

Here's a hack for the device tree overlay that can force different SPI modes, sometimes that helps!

X11 (the graphical system) has changed how it gets touchscreen input, so if you rotate the display and the calibration isn't being picked up:

Check /usr/share/X11/xorg.conf.d for a file called 10-evdev.conf 

If you don't see that file

1. You need to sudo apt-get install xserver-xorg-input-evdev, and then...
2. If you do have a 40-libinput.conf in that same directory, you must remove it even if/once evdev is installed, since it will override the 10-evdev.conf otherwise.

Thanks to cerebrate in the forums for the hint!

A small number of Adafruit PiTFT - Touchscreen Display for Raspberry Pi were manufactured in error in 2018. If you have a display from that era with a white screen issue, see this forum post for diagnosis and remedy.