It's still a step in the right direction. I think once I get my controller problems all sorted out, everything will be fine. What I'll probably just do is use your Joystick Selection tool and map everything out to just use the Xbox controller, and then the NES pads just for NES. I can still go back in and change that to the Xbox controller in the future easily enough, so I don't have to worry too much about using that "on-the-fly" method.

@dankcushions thanks!

I havent looked in a while, but last time I did in-game saves are .srm files.

While trying to be helpful, the above posts were not specific enough.

Using hints from the config files here:
/opt/retropie/configs/n64/InputAutoCfg.ini
/opt/retropie/configs/all/retroarch-joypads/WishTechnologiesAdaptoid.cfg

And the official documentation from both mupen64 and retroarch, I managed to create a configuration specific to the N64 controller with adaptoid USB<->N64.

(EDIT: The below confusion caused by one simple issue. One cannot restart emulation station to reload the /opt/retropie/configs/all/retroarch-joypads/, one has to restart the entire RPi!!! What a bug D:)
There is some confusion for me that I'm trying to work out. I set the save/load state, but somehow load state on button "12" and in the mupen config it's "DPad L = button(12)", yet start+C-left will load state... Weird stuff all around.

In WishTechnologiesAdaptoid.cfg:
#Start button
input_start_btn = "8"
#Start is now the "hotkey"
input_enable_hotkey_btn = "8"
#Left shoulder "L"
input_l2_btn = "6"
#Start (hotkey) + Left-Shoulder will exit the emulator
input_exit_emulator_btn = "6"

Full adaptoid config in /opt/retropie/configs/n64/InputAutoCfg.ini
I was using this to reference what button is what for the above changes. By default from the previously linked config, it had some issues, such as A button was C-down, C-down didn't do anything.

; Wish Technologies Adaptoid_START
[Wish Technologies Adaptoid]
plugged = True
plugin = 2
mouse = False
AnalogDeadzone = 4096,4096
AnalogPeak = 32768,32768
Mempak switch =
Rumblepak switch =
C Button D = button(1)
C Button L = button(4)
Z Trig = button(9)
Start = button(8)
Y Axis = axis(1-,1+)
DPad U = button(10)
C Button U = button(5)
B Button = button(3)
A Button = button(0)
DPad D = button(11)
X Axis = axis(0-,0+)
R Trig = button(7)
DPad R = button(13)
DPad L = button(12)
C Button R = button(2)
L Trig = button(6)
; Wish Technologies Adaptoid_END

Side note, I wanted to make sure keyboard and other controllers are disabled. I have some USB SNES style controllers, but I don't want them working with the N64 emulator.

In /opt/retropie/configs/n64/InputAutoCfg.ini
Find the "plugged" option for keyboard and other controllers you don't want to run in the N64 emulator, and change "plugged" from "True" to "False"
; Keyboard_START
[Keyboard]
plugged = False

#My case has these other USB controllers configured:
; 2Axes 11Keys Game Pad_START
[2Axes 11Keys Game Pad]
plugged = False

@tehswiftone said in Single GPIO button:

Add this inside of your controllers config, don't forget to replace button with a proper button ID. This will be similar to exiting an emulator, you will use select + button to use it. So don't worry about it taking up a button on your controller.

input_volume_down_btn = "button"
input_volume_up_btn = "button"

I have mine setup to use Up and Down on the D-pad. Just change the "btn" to "axis".

input_volume_down_axis = "+1"
input_volume_up_axis = "-1"

@Endprodukt

Here is a simple solution. Salvage an old usb keyboard, take the little controller board. Follow the traces from the esc key ( there will be only 2 of the 23 or so connections) and solder the button to those points. Basically, now you have a one key, usb keyboard. Just the esc function. It works perfect for me using an old dell keyboard. You can get fancy and make a spacebar or any other charactor the same way and the one board on mine will end up 4 buttons, 1, 2 , space and esc.~~

~~

@Evilmrt glad i could help.

I'm a total newbie about to make a very simular setup, so I wonder if this is working out for you or there are any problems?

Having one insert coin button (and not two) , and 2) having it double as select. Having Hotkey and Exit Emulator set to the same button?