xboxdrv must be installed for using xbox360 controllers with your pi:

install it by running

sudo apt-get install xboxdrv

You have to launch multiple instances of xboxdrv (one for each controller)

For example we can edit the file /etc/rc.local to start instances of xboxdrv during boot

Here is an example of what to insert in /etc/rc.local for 4 wireless pads (put this just before exit 0):

xboxdrv --trigger-as-button --wid 0 --led 2 --deadzone 4000 --silent &
sleep 1
xboxdrv --trigger-as-button --wid 1 --led 3 --deadzone 4000 --silent &
sleep 1
xboxdrv --trigger-as-button --wid 2 --led 4 --deadzone 4000 --silent &
sleep 1
xboxdrv --trigger-as-button --wid 3 --led 5 --deadzone 4000 --silent &

(replace the --wid by --id if you use wired controllers) You must swich-on your pads before booting the raspberry.

Notice the sleep 1 between each instance: this prevents the RPi from setting random controllers with random led status; adjust timing if necessary.

After reboot when your controllers are detected, you have to configure RetroPie to use them:

Go to the retroarch-joyconfig folder (binary for configuring joypads for RetroArch);

By default (if you followed the install tutorial):

cd ~/RetroPie/emulators/RetroArch/tools

Then you have to configure each controller ( For example just use the first line if you have only 1 controller):

./retroarch-joyconfig -o p1.cfg -p 1 -j 0

./retroarch-joyconfig -o p2.cfg -p 2 -j 1

./retroarch-joyconfig -o p3.cfg -p 3 -j 2

./retroarch-joyconfig -o p4.cfg -p 4 -j 3

( -o for output file, -p for player, -j for joystick id )

After this you will get 4(or less depending) cfg files to add to your default RetroPie/configs/all/retroarch.cfg config file:

sudo cat p*.cfg >> ~/RetroPie/configs/all/retroarch.cfg

(if this don’t have permissions you can do a sudo chmod 777 RetroPie/configs/all/retroarch.cfg before)

If your config is not working well, delete the joypad configuration lines in RetroPie/configs/all/retroarch.cfg before doing anything.

(Delete the lines located at the bottom of the file, starting with line input_player1_joypad_index = "0")

Now just reboot and voila !

Big Thank you to petrockblog for this tutorial.