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ROS 2 Driver for Generic Joysticks and Game Controllers

The joy package contains joy_node, and game_controller node which interface generic joysticks and game controllers to ROS 2. These nodes publish "sensor_msgs/msg/Joy" messages, which contain the state of the devices button and axes. Examples of game controllers are ones that come with recently released game consoles and their after market clones.

The game_controller_node uses SDL2's built device mapping database to give buttons and axes a consistent order in the "sensor_msgs/msg/Joy". Custom mappings can also be supplied using SDL's SDL_GAMECONTROLLERCONFIG environment variable. A third party tool can be used to create the mapping string. The joy_node supports both joysticks and game controllers but the order that buttons and axes appear with the message will dependend on the manufacturer of the device.

For game_controller_node the following tables detail the indexes of buttons and axes.

Index Button
0 A (CROSS)
1 B (CIRCLE)
2 X (SQUARE)
3 Y (TRIANGLE)
4 BACK (SELECT)
5 GUIDE (Middle/Manufacturer Button)
6 START
7 LEFTSTICK
8 RIGHTSTICK
9 LEFTSHOULDER
10 RIGHTSHOULDER
11 DPAD_UP
12 DPAD_DOWN
13 DPAD_LEFT
14 DPAD_RIGHT
15 MISC1 (Depends on the controller manufacturer, but is usually at a similar location on the controller as back/start)
16 PADDLE1 (Upper left, facing the back of the controller if present)
17 PADDLE2 (Upper right, facing the back of the controller if present)
18 PADDLE3 (Lower left, facing the back of the controller if present)
19 PADDLE4 (Lower right, facing the back of the controller if present)
20 TOUCHPAD (If present. Button status only)
Index Axis
0 LEFTX
1 LEFTY
2 RIGHTX
3 RIGHTY
4 TRIGGERLEFT
5 TRIGGERRIGHT

For joy_node run ros2 run joy joy_node in one terminal and ros2 topic echo /joy in another. Pressing buttons and moving sticks can be used to determine at which location they appear in "sensor_msgs/msg/Joy".

Supported Hardware

This nodes should work with any joystick or game controller that is supported by SDL.

Published Topics

Subscribed Topics

Parameters

  • device_id (int, default: 0)

    • The joystick device to use. ros2 run joy joy_enumerate_devices wil list the attached devices.

  • device_name (string, default: "")

    • The joystick name to use. This can be useful when multiple different joysticks are attached. If both device_name and device_id are specified, device_name takes precedence.

  • deadzone (double, default: 0.05)

    • Amount by which the joystick has to move before it is considered to be off-center. This parameter is specified relative to an axis normalized between -1 and 1. Thus, 0.1 means that the joystick has to move 10% of the way to the edge of an axis's range before that axis will output a non-zero value.

  • autorepeat_rate (double, default: 20.0)

    • Rate in Hz at which a joystick that has a non-changing state will resend the previously sent message. If set to 0.0, autorepeat will be disabled, meaning joy messages will only be published when the joystick changes. Cannot be larger than 1000.0.

  • sticky_buttons (bool, default: false)

    • Whether buttons are "sticky". If this is false (the default), then a button press will result in a 1 being output, and a button release will result in a 0 being output. If this is true, then a button press will toggle the current state of the button, and a button release will do nothing. Thus, hitting the button while it is currently 0 will switch it to 1, and keep it at 1 until the button is pressed again.

  • coalesce_interval_ms (int, default: 1)

    • The number of milliseconds to wait after an axis event before publishing a message. Since the kernel sends an event for every change, this can significantly reduce the number of messages published. Setting it to 0 disables this behavior. The default of 1 ms is a good compromise between message delays and number of messages published.

Technical note about interfacing with joysticks and game controllers on Linux

On Linux there are two different ways to interface with a joystick. The distinction only makes a difference when attempting to pass through the device into a container or virtual machine. The first interface is via the joystick driver subsystem, which generally shows up as a device in /dev/input/js0 (or other numbers at the end). This is the way that the "joy_linux" package accesses the joystick. The second way to interface is through the generic event subsystem, which generally shows up as /dev/input/event7 (or other numbers at the end). This is the way that SDL (and hence this "joy" package) accesses the joysticks.