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Frequently Asked Questions

Setup & Configuration

Which transport should I use: Zenoh or DDS?

Conduit 2.0 supports two transports — choose based on your ROS 2 middleware:

Zenoh DDS (CycloneDDS)
RMW rmw_zenoh_cpp rmw_cyclonedds_cpp
Router required Yes (rmw_zenohd) No
Network TCP/UDP to router Multicast or unicast on LAN
Distros Humble, Jazzy, Kilted, Rolling Humble, Jazzy, Kilted, Rolling
Setup Enter router IP in Settings Set discovery mode in Settings

Recommendation: Use Zenoh if you already have rmw_zenoh_cpp set up. Use DDS if your stack uses rmw_cyclonedds_cpp and you want zero-broker operation.

See transports.md for a deeper side-by-side comparison and network-requirements reference.

I used Conduit 1.x — what changed in 2.0?

Transport choice: 2.0 adds DDS (CycloneDDS) alongside Zenoh. Existing Zenoh users can keep their current router setup — Zenoh remains fully supported. DDS is opt-in via Settings → Transport.

Supported distros: Kilted and Rolling join Humble and Jazzy.

How do I connect via Zenoh?

  1. Start the Zenoh router on your ROS 2 system: 

    source /opt/ros/jazzy/setup.bash
export RMW_IMPLEMENTATION=rmw_zenoh_cpp
export ROS_DOMAIN_ID=0  # Set domain ID (0-232, default: 0)
ros2 run rmw_zenoh_cpp rmw_zenohd

  2. Find your ROS 2 system's IP address: 

    ip addr show  # Linux
ifconfig      # macOS
ipconfig      # Windows

  3. In Conduit app:

  4. Tap Settings (gear icon)
  5. Enter Router Address (e.g., 192.168.1.100)
  6. Enter Router Port (default: 7447)
  7. Enter Domain ID (must match ROS_DOMAIN_ID on host)

  8. Tap Save

  9. Enable sensors and tap Play

Important: Domain ID must match between the app and ROS 2 system. Valid range: 0-232 (RTPS specification limit).

How do I connect via DDS?

  1. On your ROS 2 system: 
    source /opt/ros/jazzy/setup.bash
export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp
export ROS_DOMAIN_ID=0  # Valid range: 0-232

# Restart the cached ros2 daemon so it picks up the new RMW.
# Skip this on a fresh shell where the daemon hasn't started yet.
ros2 daemon stop
ros2 daemon start          # optional — `ros2 topic list` autostarts it

ros2 topic list  # Verify the RMW is active (no topics expected yet)

Re-run ros2 daemon stop whenever you change RMW_IMPLEMENTATION, ROS_DOMAIN_ID, CYCLONEDDS_URI, or the unicast peer list. The daemon caches the first context it saw and silently ignores later env-var changes — symptoms include ros2 topic list showing topics from the wrong domain, missing the iOS topics entirely, or "topic exists but no data". See troubleshooting.md.

  1. In the Conduit app:
  2. Tap Settings → Transport: DDS
  3. Discovery Mode: Hybrid (recommended) or Unicast
  4. Add the ROS 2 host IP to Unicast Peers
  5. Network Interface: en0 (required on iOS — do not leave as "auto")
  6. Domain ID: must match ROS_DOMAIN_ID

  7. Tap Save

  8. Enable sensors and tap Play

Important: - Domain ID must match between the app and ROS 2 system. Valid range: 0-232 (DDS RTPS limit). - On iOS, DDS requires binding to en0 (WiFi) — multicast / auto-select often fails.

Which ROS 2 versions are supported?

Conduit supports: - ROS 2 Humble (Ubuntu 22.04) - No type hash - ROS 2 Jazzy (Ubuntu 24.04) - RIHS01 type hash - ROS 2 Kilted (Ubuntu 24.04) - RIHS01 type hash - ROS 2 Rolling - RIHS01 type hash

Supported RMW implementations: - rmw_zenoh_cpp — via Zenoh transport (the app auto-detects Humble vs Jazzy wire format) - rmw_cyclonedds_cpp 0.10.5 — via DDS transport (default RMW on many ROS 2 distributions)

Why can't I see my topics in ros2 topic list?

Check these common issues:

  1. Domain IDs don't match (most common): 
    # Check domain ID on ROS 2 system
echo $ROS_DOMAIN_ID
  2. Domain ID in app Settings must match ROS_DOMAIN_ID on host
  3. Default is 0 if not set

  4. Valid range: 0-232 (RTPS specification limit)

  5. Zenoh router not running: 

    # Start router with matching domain ID
export ROS_DOMAIN_ID=0
ros2 run rmw_zenoh_cpp rmw_zenohd

  6. Wrong RMW implementation: 

    # Verify RMW setting
echo $RMW_IMPLEMENTATION
# Should output: rmw_zenoh_cpp

  7. Network connectivity: Ensure iPhone and ROS 2 system are on the same network

  8. Firewall blocking port 7447: Check firewall settings on ROS 2 system

What's the difference between Humble and Jazzy wire modes?

  • Jazzy: Uses type hash in key expressions (RIHS01_...)
  • Humble: Uses "TypeHashNotSupported" instead of type hash
  • Auto-detect: App queries Zenoh admin space to determine version (recommended)

Use "Auto-detect" unless you're experiencing specific compatibility issues.

Can I use Conduit without a ROS 2 system?

Yes, for testing: - The iOS Simulator generates mock sensor data - You can verify app functionality without ROS 2 - However, you won't be able to receive data without a Zenoh router

For production use, you need a ROS 2 system (Humble, Jazzy, Kilted, or Rolling) with one of the supported transports: - Zenoh: rmw_zenoh_cpp middleware and a running Zenoh router (rmw_zenohd). - DDS: rmw_cyclonedds_cpp middleware on the same LAN as your iOS device — no broker required.

Which sensors work on which platforms?

Platform Available Sensors
iOS/iPadOS All 12 sensors (IMU, GPS, Camera, LiDAR*, Magnetometer, Barometer, Battery, Thermal, Proximity†, Illuminance, Microphone, Game Controller)
visionOS Camera, IMU, Game Controller
tvOS Game Controller only
macOS Camera, Battery, Game Controller

*LiDAR requires iPhone 12 Pro or newer, iPad Pro 2020+, Vision Pro †Proximity sensor only on iPhone (not iPad)

How do I enable background mode?

Background mode is a premium In-App Purchase. After unlocking it:

  1. Tap Settings → Enable "Background Mode"
  2. Grant location permission if using GPS

Limitations: - GPS background tracking not supported (privacy constraints) - Camera, LiDAR, and Microphone stop in background (iOS restrictions on ARKit and audio session) - Only IMU, GPS (foreground only), Magnetometer, Barometer, Battery, Thermal continue in background

What are the premium features?

Free features: - IMU, GPS, Magnetometer, Barometer, Battery, Thermal, Proximity, Illuminance, Microphone - Front camera

Premium features (one-time In-App Purchase per feature): - Multi-camera — Wide, ultra-wide, telephoto cameras (front camera stays free) - LiDAR sensor — Point cloud depth sensing (iPhone Pro / iPad Pro / Vision Pro) - Game Controller — MFi / Bluetooth controller input - Background mode — Continue publishing supported sensors when the app is backgrounded - MCAP Recording — Record live topics to a local .mcap file for replay in Foxglove or ros2 bag play

How do I verify data is being published?

On your ROS 2 system:

# Check if topic appears
ros2 topic list | grep conduit

# Echo data from IMU sensor
ros2 topic echo /conduit/imu

# Check publish rate
ros2 topic hz /conduit/imu

# View topic info
ros2 topic info /conduit/imu --verbose

Why is my sensor showing "Not Available"?

Common reasons:

  1. Hardware limitation: Device doesn't have that sensor
  2. LiDAR: iPhone 12 Pro+ only
  3. Barometer: iPhone 6+ only

  4. Proximity: iPhone only (not iPad)

  5. Platform limitation:

  6. visionOS: No GPS (indoor device)
  7. tvOS: Only Game Controller

  8. macOS: No IMU/GPS/Magnetometer

  9. Permission denied: Grant permission in Settings → Privacy

  10. Runtime unavailable:

  11. Game Controller: No controller connected
  12. Location: Location services disabled

Can I use multiple cameras simultaneously?

Yes! Conduit supports multi-camera streaming:

  1. Tap the Camera sensor row
  2. Select multiple cameras (front, wide, ultra-wide, telephoto)
  3. Each camera publishes to separate topic:
  4. /conduit/camera/front/compressed
  5. /conduit/camera/wide/compressed
  6. /conduit/camera/ultrawide/compressed
  7. /conduit/camera/telephoto/compressed

Note: Wide, ultra-wide, and telephoto cameras require Premium unlock.

How do I change the publishing rate?

  1. Tap the gear icon ⚙️ next to any sensor
  2. Adjust "Rate (Hz)" slider
  3. Configure QoS settings if needed
  4. Tap Save

Different sensors have different maximum rates (see Supported Sensors table).

Microphone

What ROS 2 message type does the Microphone sensor use?

The Microphone sensor publishes audio_common_msgs/msg/AudioData messages.

Audio parameters: - Sample rate: 16,000 Hz - Channels: 1 (mono) - Format: S16LE (signed 16-bit little-endian PCM) - Samples per message: 1024 - Publish rate: ~15.6 messages/sec

Default topic: /conduit/audio (configurable via namespace in Settings)

How do I receive Microphone data on ROS 2?

You need the audio_common_msgs package installed on your ROS 2 system.

Using Docker (easiest): 

# The pre-built Docker image already includes audio_common_msgs
docker run -d -p 7447:7447 --name ros_jazzy_zenoh ghcr.io/youtalk/conduit-support:jazzy

# Echo audio messages
docker exec ros_jazzy_zenoh bash -c \
  "source /opt/ros/jazzy/setup.bash && \
   source /ros2_ws/install/setup.bash && \
   export RMW_IMPLEMENTATION=rmw_zenoh_cpp && \
   ros2 topic echo /conduit/audio audio_common_msgs/msg/AudioData"

Using a native ROS 2 installation: 

# Install audio_common (includes audio_common_msgs)
sudo apt install ros-jazzy-audio-common   # Jazzy
sudo apt install ros-humble-audio-common  # Humble

# Or build from source
mkdir -p ~/ros2_ws/src && cd ~/ros2_ws/src
git clone --branch ros2 --depth 1 https://github.com/ros-drivers/audio_common.git
cd ~/ros2_ws
rosdep install --from-paths src --ignore-src -r -y
colcon build --packages-select audio_common_msgs
source install/setup.bash

Verify the topic: 

# Check topic exists
ros2 topic list | grep audio

# Echo messages
ros2 topic echo /conduit/audio audio_common_msgs/msg/AudioData

# Check publish rate (~15-16 Hz)
ros2 topic hz /conduit/audio

# Inspect message type
ros2 topic info /conduit/audio --verbose

How do I play back the audio data in Python?

import rclpy
from rclpy.node import Node
from audio_common_msgs.msg import AudioData
import numpy as np
import sounddevice as sd

class AudioPlayer(Node):
    def __init__(self):
        super().__init__('audio_player')
        self.subscription = self.create_subscription(
            AudioData,
            '/conduit/audio',
            self.audio_callback,
            10)
        self.sample_rate = 16000

    def audio_callback(self, msg):
        # Convert bytes to int16 numpy array
        samples = np.frombuffer(bytes(msg.data), dtype=np.int16)
        # Normalize to float32 [-1.0, 1.0]
        audio = samples.astype(np.float32) / 32768.0
        # Play audio (non-blocking)
        sd.play(audio, self.sample_rate)

def main():
    rclpy.init()
    player = AudioPlayer()
    rclpy.spin(player)

if __name__ == '__main__':
    main()

Does the Microphone sensor work in the background?

No. iOS restricts microphone access to foreground apps only. The microphone stops when the app is backgrounded.

Keep the app in the foreground when using the Microphone sensor.

MCAP Recording

How does MCAP recording work?

When you start a recording, Conduit writes every published topic — same XCDR v1 bytes as the live Zenoh / DDS publish path — to a local .mcap file in the app's Documents directory. Schemas are embedded in the MCAP header automatically, so the bag round-trips through any MCAP-aware reader (Foxglove, ros2 bag play, the mcap CLI) without external .msg files.

Recordings are saved on-device only. Conduit never uploads them. From the in-app Recordings list you can share a recording via the system share sheet (Files, AirDrop, mail, …) or delete it.

Can I record while publishing live to ROS 2?

Yes. Recording is a tee on the same publish path, not a separate pipeline — every message you send to ROS 2 is also written to the bag.

How do I replay an MCAP file?

# Foxglove Studio: File → Open → select the .mcap

# ros2 bag (Jazzy / Kilted / Rolling — bundled mcap_storage_plugin):
ros2 bag play recording.mcap

# Humble: install ros-humble-rosbag2-storage-mcap first
sudo apt install ros-humble-rosbag2-storage-mcap
ros2 bag play recording.mcap --storage mcap

Why is the Recording button greyed out?

MCAP Recording is a one-time In-App Purchase (see premium features). After unlocking it, the Recording control becomes active in the FAB mode selector.

Does Conduit work offline?

No. Conduit requires network connectivity to: - Connect to Zenoh router on your local network - Publish sensor data to ROS 2 topics

However, no internet is required - only local network between your iOS device and ROS 2 system.

How do I reset app settings?

  1. Delete and reinstall the app, OR
  2. iOS Settings → Conduit → Reset (if available)

This will clear: - Saved router address - Sensor configurations - Premium purchase status is preserved (linked to Apple ID)

Is my data sent to the cloud?

No. All sensor data: - Stays on your local network - Sent only to your configured Zenoh router - Never uploaded to external servers - Never shared with third parties

Firebase Analytics collects anonymous app usage statistics only (opt-out available in iOS Settings).

See our Privacy Policy for details.