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RadioMaster - TX16S MKII

TX16S Mark II Radio Controller by RadioMaster offers reliable and precise remote control on long distances. It is a very popular choice among UAV pilots and roboticists.

The device operates on a 2.4 GHz frequency, utilizing LoRa modulation to increase signal range over traditional gamepads, and is equipped with a large color touchscreen, providing a user-friendly interface for configuration and telemetry data.

RadioMaster TX16S

Sources:

Getting started​

To run the RadioMaster TX16S, you must meet certain requirements listed below:

Software​

Hardware​

  • Hardware receiver dongle (ELRS receiver with an integrated USB to UART converter) connected to a USB port of the User Computer.

Demo​

husarion_ugv_crsf_teleop package creates a ROS 2 node, allowing control of the ROS-powered mobile and manipulation robots with a CRSF compatible RC remote such as RadioMaster TX16S. crsf_teleop node converts received CRSF packets from the receiver dongle to geometry_msgs/Twist message type in order to provide velocity commands for the robot.

The result of this demo will be the publication of a velocity messages on the ROS topic /cmd_vel. An example with a mobile robot will be described below.

Start guide​

1. Setup udev rules​

caution

If you are using Husarion OS, you can skip this step as the udev rules are already set up.

To be able to distinguish between connected devices it is necessary to add a rule that aliases detected hardware dongle to a known symlink file.

Open (or create) the udev rules file:

sudo nano /etc/udev/rules.d/99-local.rules

Append the following line to the file:

ACTION=="add", ,ATTRS{interface}=="PAD02 Dongle", SYMLINK+="ttyUSBPAD"

Press ctrl + o and then ctrl + x to save and quit.

Reload rules by executing:

sudo udevadm control --reload-rules
sudo udevadm trigger

2. Test receiver dongle​

Connect receiver dongle to the USB port of the User Computer. You can verify that the device is detected by typing:

ls /dev | grep "ttyUSBPAD"

You should see a file named ttyUSBPAD in the output.

3. Clone repository​

git clone https://github.com/husarion/husarion_ugv_crsf_teleop.git
cd husarion_ugv_crsf_teleop

4. Edit Parameters File​

By default the node is set up to work with Panther robot. To load Lynx configuration, you need to change the params_file parameter in the docker-compose.yml file.

command: >
      ros2 launch husarion_ugv_crsf_teleop teleop.launch.py params_file:=/config/crsf_teleop_lynx.yaml

Default parameter files for Panther and Lynx can be found in the husarion_ugv_crsf_teleop/config directory and can be changed directly. Custom parameters file can be provided by setting the params_file launch argument.

5. Start Docker service​

docker compose up -d

You can view the logs of the running container by typing:

docker compose logs -f

After a successful connection to the RC remote, you should see the following message:

[panther.crsf_teleop]: Connected
[panther.crsf_teleop]: Link quality restored: 100%

Result​

Exec into running container:

docker compose exec -it husarion_ugv_crsf_teleop /bin/bash

Now you should see the relevant ROS 2 topic:

user@docker:~$ ros2 topic list
/panther/cmd_vel
/panther/link_status
/parameter_events
/rosout

Tilting sticks on the RC controller should result in /cmd_vel topic being updated with velocity commands. Namespace fields should be updated with used robot model name (e.g. panther).

ros2 topic echo /<namespace>/cmd_vel

Additionally, you can check the link status by echoing the /link_status topic:

ros2 topic echo /<namespace>/link_status

Sticks are mapped to the following axes:

  • Left stick horizontal: angular velocity
  • Right stick vertical: linear velocity

RC controller has some additional buttons that can be used for different functionalities:

  • SG switch - tri-state switch, selects robot speed from values specified in the parameters yaml file (slow, normal, fast)
  • SF switch - emergency stop
  • SA switch (down position) - silence cmd_vel messages, allows other nodes to control the robot while enabling e_stop functionality
caution

By default the SA switch has no functionality assigned. You can enable silence mode by adding the following line to the custom params.yaml file:

silence_cmd_vel: true

ROS 2 API​

husarion_ugv_crsf_interfaces​

Contains custom message definitions for the husarion_ugv_crsf_teleop node. Currently, it only contains the LinkStatus message.

husarion_ugv_crsf_teleop​

The main package for controlling robots using a CRSF compatible remote control. A receiver should be connected to the robot's computer via USB-UART converter or be integrated as a hardware USB dongle. The CRSF protocol parser is implemented based on the following specification.

Launch Files​

  • teleop.launch.py: Launches crsf_teleop_node node. Automatically respawns node if a remote controller is connected. A namespace of a node can be set using the namespace launch argument. A custom parameters file can be provided by setting the params_file launch argument.
Parameters​
  • namespace [string, default: ""]: Namespace for the node.
  • params_file [string, default: config/crsf_teleop_${ROBOT_MODEL}.yaml]: Path to the crsf_teleop_node parameters file.

Configuration Files​

  • crsf_teleop_panther.yaml: Sets default Panther robot parameter values for the crsf_teleop_node when teleop.launch.py is launched.
  • crsf_teleop_lynx.yaml: Sets default Lynx robot parameter values for the crsf_teleop_node when teleop.launch.py is launched.

ROS Nodes​

crsf_teleop_node​

Translates received CRSF commands to velocity commands for the robot.

The following channels are used for controlling the robot via the TX16S remote control:

  • Channel 2 - Right gimbal up/down - forward/backward velocity
  • Channel 4 - Left gimbal left/right - turning (angular) velocity
  • Channel 5 - SF switch - emergency stop
  • Channel 7 - SA switch (down position) - silence cmd_vel messages, allows other nodes to control the robot while enabling e_stop functionality
  • Channel 11 - SG switch - tristate switch, selects robot speed
Publishes​
  • cmd_vel [geometry_msgs/Twist]: Publishes velocity commands to the robot.
  • link_status [panther_crsf_teleop_msgs/LinkStatus]: Describes a radio link status between the remote control and the robot. Parameters are described in the CRSF_FRAMETYPE_LINK_STATISTICS frame documentation.
Service Clients​
  • hardware/e_stop_trigger [std_srvs/Trigger]: Triggers an emergency stop.
  • hardware/e_stop_reset [std_srvs/Trigger]: Resets an emergency stop.
Parameters​
  • serial_port [string, default: /dev/ttyUSB0]: Serial port to which the CRSF receiver is connected.
  • baudrate [int, default: 576000]: Baudrate of the serial port.
  • e_stop_republish [bool, default: False]: Rebroadcasts asserted emergency stop signal once per second. Will override other emergency stop sources.
  • enable_cmd_vel_silence_switch[bool, default: False]: Enables remote to disable publishing cmd_vel messages on demand. Can be used as a remote emergency stop when using other nodes to control the robot.
  • linear_speed_presets [double_array, default: [0.5, 1.0, 2.0]]: Selectable robot maximum linear speed for cmd_vel topic.
  • angular_speed_presets [double_array, default: [0.5, 1.0, 2.0]]: Selectable robot maximum angular speed for the cmd_vel topic.

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