Once you have the display wired up, its time to test your wiring by uploading the example code we have written. Again, we suggest using an Arduino to test.
Go to the Arduino Library manager under Sketch → Include Library → Manage Libraries...
From within the Library manager, start by installing Adafruit GFX:
Then look for and install the Adafruit ILI9341 library
Note that this display has an ILI9340 but we still use the ILI9341 library, it's OK! The chips are nearly identical
If using an older Arduino IDE (pre-1.8.10), also locate and install Adafruit_BusIO (newer versions do this one automatically).
Restart the Arduino IDE. You should now be able to select File → Examples → Adafruit_ILI9341 → graphicstest sketch. Upload the sketch to your Arduino wired as before
Once uploaded, the Arduino should perform all the test display procedures! If you're not seeing anything - first check if you have the backlight on, if the backlight is not lit something is wrong with the power/backlight wiring. If the backlight is lit but you see nothing on the display make sure you're using our suggested wiring.