I have a 7 inch touchscreen from waveshare. The touchscreen works via HDMI to get the image and the power and touch function goes via usb to the pi. So the power comes from the pi...
The problem here is, I draw way too much amps from my pi when I turn the screen on... now what I want to acheve is that I can use the touchscreen as normal, but provide power to it via an extern power supply. So when I did this on the standard usb input, the touch stopped working. How can I fix this issue so I can have the touchscreen powered from an extern power supply but still have another usb cable that runs to the pi to get the touch to work?
To make it clear, some diagrams have been added.
And this is how I want it, but I don't know if this is possible or not and how I should dot it: