cras_joy_tools

Joystick and gamepad handling tools.

Python module cras_joy_tools.history_joystick

Stateful gamepad/joystick library. It allows querying for button state changes, button combos etc.

API documentation is available at https://docs.ros.org/en/api/cras_joy_tools/html/index.html .

Node joy_translator

The task of joy_translator is to “translate” the joy_node outputs so that the button/axes indices are the same as for a referential gamepad (which might even be virtual). This allows writing code that doesn’t need to care about which particular type of joystick (in which mode) is plugged in.

The translator is implemented in module cras_joy_tools.joy_translator and uses configuration files from cras_joy_tools/joy_mappings (or a custom folder).

The launch file cras_joy_tools/launch/joy_translator.launch has an argument called transparent_translation. If it is true, the translated data are published to the joy topic, and the “raw” (untranslated) data are published to topic joy_raw. If transparent_translation is false, the joy topic contains the untranslated data, and topic joy_translated contains the translated data.

Gamepad translation config format

Each translation config for a gamepad should be a YAML file. If the gamepad appears under /dev/input/by-id, then name the file according to this name (replacing any occurence of serial number with string SERIAL). If the gamepad does not appear there, name the file as you like.

The following keys are required:

• device_ids (list of string): List of VID:PID strings identifying the gamepad. You can either see them in lsusb or in /proc/bus/input/devices.
• num_buttons (int): The expected number of buttons of the Joy messages produces by joy_node.
• num_axes (int): The expected number of axes of the Joy messages produces by joy_node.
• deadzone (double, optional): If set, this will be a gamepad-specific deadzone. Otherwise, a default is used.
• buttons (dict[int->str]): Mapping of input buttons and axes to the translated buttons.
• axes (dict[int->str]): Mapping of input buttons and axes to the translated axes.
• init (dict[str->str]): Expressions to evaluate when the gamepad connects.
• callbacks (dict[str->str]): Callbacks to evaluate when a new Joy message is received.

The values in buttons, axes, init and callbacks are expressions passed to eval(), so you can use a bit of Python programming inside (e.g. math operations).

While evaluating the expressions, these variables are accessible:

• a: a list of raw axis values
• b: a list of raw button values
• pa: a list of raw axis values in the previous message
• pb: a list of raw button values in the previous message
• vars: a dictionary of user-defined variables (you should initialize them in the init section)

In section init, you can add key-value pairs, where the key doesn’t matter (it’s just a nice name), and the value is passed to eval() during startup of the translator. This is nice for initializing user variables in the vars dict.

Section callbacks is similar to init, but the values are evaluated after each message is processed. You can e.g. change values in the vars dictionary from the callbacks.

Adding a new gamepad model

Attach the gamepad to your computer. From ls -l /dev/input/by-id/ find out the device name (let’s call it $DEV_NAME). If $DEV_NAME contains a serial number nearby the end of it, replace the serial number with string SERIAL. Then create file named $DEV_NAME.yaml (best by copying an existing file). If you don’t see the device in by-id, then give the file a name you like.

Now issue a lsusb in console and try to find the vendor:model pair for the gamepad. Put this ID in the device_ids list in the created config file. If the gamepad is not there, you will find it in /proc/bus/input/devices. Search for js0.

Next, edit the created YAML file. In one console run rosrun joy joy_node, in another one run rostopic echo /joy. Now observe the output of the /joy topic and try to match button/axis indices to the expressions in the YAML file.

Node position_joy_cmd

Send relative positional commands by pressing gamepad buttons. This command interface is expected to work with cras_relative_positional_controller.

Subscribed topics:

• ~joy (:sensor_msgs:Joy): The input joystick.

Published topics:

• ~goal (:cras_cras_relative_positional_controller:RelativeMoveActionGoal): Goal for the position controller.

Used actions:

• position_controller (:cras_cras_relative_positional_controller:RelativeMoveAction): The relative positional controller.

Parameters:

• ~use_action (bool, default True): If true, the action interface will be used. Otherwise, just the ~goal will be published.
• ~lin_dist_slow (double, default 0.1): The distance to drive in slow mode.
• ~lin_dist_fast (double, default 0.5): The distance to drive in fast mode.
• ~lin_vel_slow (double, default 0.1): Slow velocity.
• ~lin_vel_fast (double, default 0.3): Fast velocity.
• ~ang_dist_slow (double, default 0.4): The angular distance to drive in slow mode.
• ~ang_dist_fast (double, default 1.5): The angular distance to drive in fast mode.
• ~ang_vel_slow (double, default 0.4): Slow angular velocity.
• ~ang_vel_fast (double, default 0.8): Fast angular velocity.
• ~deadman_slow (int, default 1): Index of the deadman button that needs to be pressed to execute slow motion.
• ~deadman_fast (int, default 3): Index of the deadman button that needs to be pressed to execute fast motion.
• ~axis_linear (int, default 7): Index of the joystick axis that defines linear motion.
• ~axis_angular (int, default 6): Index of the joystick axis that defines the angular motion.