ROS 2 Driver for Generic Linux Joysticks

The joy_linux package contains joy_linux_node, a node that interfaces a generic Linux joystick to ROS. This is a lightweight, Linux-only node with no external dependencies. If you are on an embedded type Linux system and need a joystick driver, this driver may be for you. For all other use cases, the more modern, cross-platform, and supported "joy_node" should be used instead.

Supported Hardware

This node should work with any joystick that is supported by Linux.

Published Topics

• joy (sensor_msgs/msg/Joy): outputs the joystick state.

Device Selection

There are two parameters controlling which device should be used:

• ~dev (string, default: "/dev/input/js0")
• ~dev_name (string, default: "" (empty = disabled))

If ~dev_name is empty, ~dev defines the Linux joystick device from which to read joystick events.

If ~dev_name is defined, the node enumerates all available joysticks, i.e. /dev/input/js*. The first joystick matching ~dev_name is opened. If no joystick matches the desired device name, the device specified by ~dev is used as a fallback.

To get a list of the names of all connected joysticks, an invalid ~dev_name can be specified. For example:

ros2 run joy_linux joy_linux_node --ros-args -p dev_name:="*"

The output might look like this:

[ INFO]: Found joystick: ST LIS3LV02DL Accelerometer (/dev/input/js1).
[ INFO]: Found joystick: Microsoft X-Box 360 pad (/dev/input/js0).
[ERROR]: Couldn't find a joystick with name *. Falling back to default device.

Then the node can be started with the device name given in the list. For example:

ros2 run joy_linux joy_linux_node --ros-args -p dev_name:="Microsoft X-Box 360 pad"

Advanced Parameters

• ~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. Linux does its own deadzone processing, so in many cases this value can be set to zero.

• ~autorepeat_rate (double, default: 0.0 (disabled))

  • Rate in Hz at which a joystick that has a non-changing state will resend the previously sent message.

• ~coalesce_interval (double, default: 0.001)

  • Axis events that are received within coalesce_interval (seconds) of each other are sent out in a single ROS message. Since the kernel sends each axis motion as a separate event, coalescing greatly reduces the rate at which messages are sent. This option can also be used to limit the rate of outgoing messages. Button events are always sent out immediately to avoid missing button presses.

Further Information

For further information have a look at the Wiki page.