estop

ROS 2 package to bridge an Arduino-based emergency stop button to:

• ROS 2 topics:
  • /estop/triggered (std_msgs/Bool)
  • /estop/plugged_in (std_msgs/Bool)
• Optional raw CycloneDDS topic:
  • h12/estop_status_raw
    • type h12.estop.EstopStatusRaw
    • fields: triggered (bool), plugged_in (bool), sequence_id (int), stamp_ms (int, epoch time)

Behavior

• Continuously attempts to connect to /dev/ttyACM0 (configurable).
• Parses serial lines from Arduino in format ESTOP,0 / ESTOP,1.
• Publishes status at fixed rate (100 Hz default) even when disconnected.
• Applies software debounce (state_debounce_sec=0.08 default) to suppress spurious state flip-flops.
• plugged_in=false when serial cannot be opened or data goes stale.
• Applies startup stale grace (stale_connect_grace_sec=1.5) to avoid false stale warnings right after connect.
• NOTE: Fail-safe mode forces triggered=true while disconnected.

Architecture

• estop/serial_interface.py: serial discovery, probe, parsing, stale handling, and reconnect.
• estop/estop_node.py: ROS 2 + raw DDS publisher only.
• estop/serial_status_test.py: standalone serial parser test executable.

Arduino Firmware

Flash arduino/estop_serial.ino to your UNO.

Default configuration:

• Digital pin: 13
• Serial baud: 115200
• Message format: ESTOP,0|1

Dependencies

ROS dependencies are declared in package.xml.

Python runtime dependencies:

• required: pyserial
• optional for raw DDS publishing: cyclonedds

If you are using a venv without pip in this workspace, use uv pip:

uv pip install --python .venv310/bin/python pyserial cyclonedds

USB Serial Access

Run the following command to grant the current user access to the serial port:

# allow current user to access USB serial devices
sudo usermod -a -G dialout $USER
# then log out and back in

Build

From ros2 workspace root (one level above src):

colcon build --paths src/estop
source install/setup.bash

Run

ros2 launch estop estop.launch.py

Or run node directly:

ros2 run estop estop_node

Override publish rate if needed:

ros2 run estop estop_node --ros-args -p publish_rate_hz:=200.0

If your wiring is noisy or the button bounces, increase debounce window:

ros2 run estop estop_node --ros-args -p state_debounce_sec:=0.15

If you see package 'estop' not found, source the workspace in the same shell you launch from:

cd /home/humanoid/ws_ctrl
source install/setup.bash
ros2 pkg list | grep '^estop$'

Useful checks

ros2 topic echo /estop/triggered
ros2 topic echo /estop/plugged_in

If raw_dds_enabled is true and cyclonedds is installed, the node also writes raw DDS samples on h12/estop_status_raw.

Raw CycloneDDS subscriber test

Run the ROS-side publisher first, then in another shell:

cd /home/humanoid/ws_ctrl
source install/setup.bash
ros2 run estop estop_raw_dds_subscriber

Optional topic override:

ros2 run estop estop_raw_dds_subscriber -- --topic h12/estop_status_raw

Serial parser test (no ROS topics required)

This directly exercises estop serial discovery + parsing:

cd /home/humanoid/ws_ctrl/src/estop
conda deactivate
python3 scripts/estop_serial_test.py \
  --serial-port /dev/serial/by-id/usb-Arduino__www.arduino.cc__0043_55338343539351817262-if00

This script is fully outside ROS 2 (no ros2 run, no workspace sourcing).

Safe unique estop port selection

The node now supports robust matching with probe validation so it does not attach to the wrong serial device.

Recommended order:

1. Use /dev/serial/by-id/* if available.
2. Set exact USB serial_number if your adapter exposes one.
3. Optionally constrain by usb_vid and usb_pid.
4. Keep require_estop_signature=true so the node only accepts devices emitting ESTOP,BOOT or ESTOP,0|1.

Defaults tuned for unplug/replug robustness:

• probe_timeout_sec=3.0
• publish_rate_hz=100.0
• line_stale_timeout_sec=0.1
• stale_connect_grace_sec=1.5
• stale_reopen_timeout_sec=3.0
• reconnect_interval_sec=1.0

Example launch overrides:

ros2 run estop estop_node --ros-args \
  -p serial_port:=/dev/serial/by-id/usb-Arduino__www.arduino.cc__0043_XXXXXXXX-if00 \
  -p require_estop_signature:=true

or auto-discovery with USB filters:

ros2 run estop estop_node --ros-args \
  -p serial_port:="" \
  -p usb_vid:=9025 \
  -p usb_pid:=67 \
  -p require_estop_signature:=true