I have an Adafruit ILI9341 320x420 (STMPE610 or FT620) PiTFT 2.8-inch display with resistive touch. See the attached image for a view ofthe back. It is the model with four buttons along one side and two headers. The display works fine when I use the female header on it to connect to the Raspberry Pi's GPIO header, even if the configuration script is opaque voodoo.
Now I need to be able to use this screen on another Raspberry Pi where it shares the header with three, somtimes four, other devices. I suspect that the easiest way to do that is to just run wires from one of the headers on the PiTFT to the correspondng pins on the header on the Raspberry Pi. I'm not finding anything for the 2.8-inch model at pinout.xyz, but the 3.5-inch model suggests that pin 2 is used on the PiTFT and pin 4 is not used. Pin 2 (+5V) on the Raspberry Pi is already spoken for by another peripheral, so I plan to connect the PiTFT to Pin 4 (also +5V) on the Raspberry Pi instead.
I'm using two of the PiTFT's ground pins: pin 6 and pin 39 and suppose that is enough. But I wonder about the voltage in. I apologize for the dumb question, but should I connect +5V from the Raspberry Pi to pin 2 or pin 4 on the PiTFT, or does that matter at all since on the Pi they are both +5V? I'm guessing the pin 2, but want to make sure before powering it on.
Or maybe a second question, where may I find an authoritative source for the pinouts for the Adafruit ILI9341 320x420 (STMPE610 or FT620) PiTFT 2.8-inch resistive touch display? I see the one for the 3.5-inch model but not the 2.8-inch model.