How Do Emulators Differentiate The Same Controllers

[RCKJ]

Ok, I will try to word this so its understandable. ?

I have 2 Wireless Official Xbox 360 Controllers running with an official Microsoft Wireless Adapter with no issues.

My question is how do emulators like EPSXE and PCSX2 and others differentiate which controller is player 1 and player 2 when both controllers are the same brand.

I have never used any emulator with 2 players, always 1 player.

I hope the question is easy to understand.

Edited June 26, 2018 by RCKJ

[Lordmonkus]

It uses the USB port to tell them apart, each one has a different ID.

[mothergoose729]

Xbox controllers are xinput devices. Windows keeps track of your connected controllers and gives them priority. Usually its a first come first served basis, but it can get weird of windows thinks there are more controllers connected then there actually are. 

Other controllers use the dinput standard, which gives no preferences. Each device has a unique ID and each button on the controller has a specific button index ie 'A' might be 0, 'B' might be 1, ect. 

When registering inputs in an emulator it generally just correlates a device and a particular input with certain controls. You can pretty easily configure player one to be a combination of button inputs from two different controllers if you want. Emulators that are Xinput aware are able to read the correct profile from the driver automatically, as every Xinput device is basically treated like a 10 button Xbox pad with button indexes 0-9, a digital Dpad, and two analog inputs. Dinput devices not need follow this standard. Any particular index can correspond to any random button on the controller, and the emulator needs your help in order to figure out the correct mapping.