So what I plan to do is make a raspberry pi into a switch and make detachable controllers. From my research I believe that I should be using an Arduino Nano for the controller and some sort of bluetooth connector to send the data.
I want to be able to use the controllers wirelessly and then be able to plug them into the "switch" to charge and play wired. This would ideally also be able to charge the controllers when you plug them in. So far I have gotten to laying out the power circuit in my head which consists of a lithium battery charger which connects to the battery and then have some sort of board to step up the power to 5V so I can input it into the Arduino.
The Arduino would take the button presses and send them over bluetooth to the "switch". There would be 7-8 buttons and an analog joystick on the controller although I'd probably want to add more if I could.
The problem I am working through right now is charging the controller battery while also sending data from the Arduino. I believe that I would like to use a micro usb connection between the "switch" and the controller which would supply power and take in data.
My question currently is can I splice the micro usb connection to take the power and ground and input them into the battery while taking the data from the Arduino. I think it would be cool if I could plug it into a computer and have it work as a controller but if that is unreasonable then its fine without that functionality.