This repository provides examples of reading gamepad data in a Linux system. Examples are written in C and python.

Linux has two different joystick interfaces.

1. /dev/input/jsX maps to the joystick API interface
2. /dev/input/event* maps to the evdev interface.

1. Testing the gamepad with the Joystick API interface

   • The button on the back of the controller should be in the X position
   • Plug the gamepad into a usb port and open up a terminal
   • Type lsusb and you should see similar output: Bus 001 Device 007: ID 046d:c21d Logitech, Inc. F310 Gamepad [XInput Mode] If you do not see the above, then check the switch on the back is likely not in the X position.
   • With the switch in the X position, you can use the jstest program to verify the controller works. To install jstest, type sudo apt install joystick. Now type jstest and press the enter key. The output provides the following choices:

   Usage: jstest [<mode>] <device>
   Modes:
   --normal           One-line mode showing immediate status
   --old              Same as --normal, using 0.x interface
   --event            Prints events as they come in
   --nonblock         Same as --event, in nonblocking mode
   --select           Same as --event, using select() call
   

   • Before running the program, you will need the device information. Type ls /dev/input for a listing of input devices.

   by-id    event0  event10  event12  event14  event16  event3  event5  event7  event9  mice    mouse1
   by-path  event1  event11  event13  event15  event2   event4  event6  event8  js0     mouse0
   

   The joystick devices are listed as jsX, where the X is a placehoder for a number. In the example output above, the device is js0. When running the jstest program, the path /dev/input/js0 is needed.

   • Type either jstest /dev/input/js0 or jstest --normal /dev/input/js0. The default mode is normal. You will see the joystick output on the screen. Move the thumbsticks and press the buttons to see the range of values.

   Driver version is 2.1.0.
   Joystick (Logitech Gamepad F310) has 8 axes (X, Y, Z, Rx, Ry, Rz, Hat0X, Hat0Y) and 11 buttons (BtnA, BtnB, BtnX, BtnY, BtnTL, BtnTR, BtnSelect, BtnStart, BtnMode, BtnThumbL, BtnThumbR).
   Testing ... (interrupt to exit)
   Axes:  0:     0  1:    -2  2:-32767  3:     0  4:    -2  5:-32767  6:     0  7:     0 
   Buttons:  0:off  1:off  2:off  3:off  4:off  5:off  6:off  7:off  8:off  9:off 10:off 
   

   • If the program does not run, check the device permissions. Type ls -l /dev/input/js0

2. Testing the gamepad with the evdev interface

   • The button on the back of the controller should be in the D (direct input) position
   • Plug the gamepad into a usb port and type lsusb in the terminal. You should see similar output: Bus 001 Device 014: ID 046d:c216 Logitech, Inc. Dual Action Gamepad
   • Find the joystick event number. Type ls -l /dev/input/by-id/ and look for an ouput similar to `lrwxrwxrwx 1 root root 10 May 9 17:39 usb-Logitech_Logitech_Dual_Action_BBECCB89-event-joystick -> ../event16'
   • Type evtest and it will list input devices and their event numbers, similar to the output below.

   No device specified, trying to scan all of /dev/input/event*
   Not running as root, no devices may be available.
   Available devices:
   /dev/input/event16:	Logitech Logitech Dual Action
   Select the device event number [0-16]: 
   

   Enter the event number, 16 in this example and press the enter key. You will then see a listing of event codes and values. Press the gamepad buttons and thumbsticks to see the full range.

A thorough and much better explanation of joysticks in Linux is found here.

Install python evdev

pip install evdev