SkyRelay Conduit

1. Safety & Regulatory Compliance

2. Product Overview

The SkyRelay Conduit is a compact, LTE-connected telemetry gateway for unmanned aircraft systems. It streams real-time flight data from your aircraft to the SkyRelay cloud over cellular, providing live position, attitude, and system health from anywhere with LTE coverage.

Key Features

• LTE Cellular Telemetry — real-time MAVLink telemetry over 4G LTE via Hologram global SIM
• MAVLink TCP Relay — connect Mission Planner, QGroundControl, or any GCS over TCP
• MQTT Cloud Streaming — telemetry published every second to the SkyRelay cloud
• Bluetooth Classic — wireless SPP connection to flight controllers (no wires required)
• Remote ID Relay — BLE scanner detects nearby ASTM F3411-22a Remote ID broadcasts
• OTA Firmware Updates — update firmware over-the-air from the dashboard
• Companion Battery Monitoring — onboard 18650 LiPo with voltage and charge tracking
• Web Dashboard — live telemetry, map view, command interface, and device settings

Supported Autopilots

• ArduPilot (Copter, Plane, Rover) — all versions with MAVLink
• PX4 — all versions with MAVLink

3. What's in the Box

4. Hardware Overview

Board Layout

The Conduit is built on the LilyGo T-SIM7600 development board, combining an ESP32-WROVER-E microcontroller with a SIM7600NA LTE modem on a single PCB.

LED Indicators

Power Options

• USB-C (5V) — bench power, programming, and battery charging
• JST connector (4.4–6V) — aircraft BEC power for in-flight operation
• 18650 Battery — backup power, auto-charges when external power is connected

5. Getting Started

Step 1: Check the SIM Card

Your Conduit ships with a Hologram global IoT SIM pre-installed. Verify the nano-SIM is seated in the slot on the underside of the board. No SIM activation is required — it is pre-provisioned.

Step 2: Connect Antennas

Screw the LTE antenna onto the main SMA connector. Optionally connect the GPS antenna to the secondary SMA connector for modem GPS fallback (the primary GPS source is the flight controller).

Step 3: Power On

Connect USB-C or apply 4.4–6V to the JST connector. The green power LED illuminates and the Conduit begins its boot sequence:

1. Derives device serial number from ESP32 MAC address
2. Loads environment configuration from internal storage
3. Initializes cellular modem and establishes LTE connection
4. Checks MAVLink UART for flight controller heartbeat
5. Connects to SkyRelay MQTT broker and begins telemetry streaming

Boot typically completes in 15–20 seconds.

Step 4: Activate Your Device

Scan the QR code on the activation card included with your Conduit. This opens the SkyRelay activation page where you can:

• Create an account or sign in
• Bind the device to your account
• Access the live telemetry dashboard

Each Conduit has a unique serial number (e.g., SC20A6C22A13D8) printed on the activation card and visible in the dashboard.

6. Flight Controller Wiring

UART Connection

The Conduit communicates with the flight controller over MAVLink serial at 115200 baud. Connect the UART pins as follows:

Recommended FC Telemetry Port Settings

ArduPilot — configure the telemetry port (e.g., SERIAL2):

• SERIAL2_PROTOCOL = 2 (MAVLink 2)
• SERIAL2_BAUD = 115 (115200)

PX4 — configure the telemetry port (e.g., TELEM2):

• MAV_1_CONFIG = TELEM 2
• SER_TEL2_BAUD = 115200

Important: The Conduit UART is fixed at 115200 baud. The flight controller telemetry port must match this speed.

7. Bluetooth Connection

The Conduit supports Bluetooth Classic SPP (Serial Port Profile) as a wireless alternative to UART wiring. This allows a cable-free MAVLink connection to your flight controller.

Requirements

• Flight controller with a Bluetooth SPP adapter (e.g., HC-05, HC-06, or built-in BT on some FC boards)
• Bluetooth adapter must be paired/discoverable

Connecting via Dashboard

1. Open the SkyRelay dashboard and navigate to the Telemetry page
2. In the Bluetooth section, click Scan to discover nearby BT devices
3. Select your flight controller from the device list
4. Click Connect — the Conduit establishes an SPP link
5. MAVLink data automatically switches from UART to Bluetooth

Auto-Reconnect

Once a flight controller is connected via Bluetooth, the Conduit saves the device address and name. On subsequent boots or disconnections:

• The Conduit automatically scans for the saved FC
• If found, it reconnects without user intervention
• If the connection drops mid-flight, it retries with exponential backoff (3s, 10s, 30s, 60s)
• During reconnection, MAVLink falls back to UART so wired data continues flowing

Auto-reconnect can be toggled on/off from the Settings tab in the dashboard.

Disconnecting

Use the Disconnect button in the dashboard to drop the Bluetooth link. MAVLink reverts to UART immediately. The saved FC target is preserved for future auto-reconnect.

8. Dashboard

The SkyRelay dashboard provides real-time monitoring and control of your Conduit and connected aircraft. Access it at your SkyRelay account URL after device activation.

Telemetry Tab

Live data updated every second:

• UAV Status — armed/disarmed, flight mode, system state
• GPS — latitude, longitude, altitude, satellites, fix type
• Attitude — roll, pitch, yaw angles
• Flight Battery — voltage, current, remaining percentage
• Conduit Status — LTE signal, cellular connection, firmware version
• Companion Battery — voltage, percentage, charging status
• Bluetooth — connection state, device name, auto-reconnect status
• Nearby Aircraft — Remote ID detections with position, speed, and signal strength

Map Tab

Live position plotted on an interactive map. Shows the aircraft's current location, heading, and altitude.

Commands Tab

Send commands to the flight controller through the Conduit:

Settings Tab

• Bluetooth Auto-Connect — toggle automatic BT reconnection to saved FC
• Device Info — serial number, firmware version, IMEI, environment

Help Tab

Quick-start guide for connecting a GCS (Mission Planner, QGroundControl) over TCP, plus links to documentation and compliance certificates.

9. OTA Firmware Updates

The Conduit supports over-the-air firmware updates via the LTE connection. No USB cable or physical access is required.

Checking for Updates

The Conduit automatically checks for updates on boot. You can also manually trigger a check from the dashboard by sending the ota_check command. The dashboard displays the current and available firmware versions.

Installing an Update

1. From the dashboard, send the ota_update command
2. The Conduit downloads the new firmware binary over LTE
3. Progress is reported in real-time via MQTT (visible in dashboard)
4. After download and verification, the Conduit reboots with the new firmware
5. If the update fails, the Conduit rolls back to the previous version automatically

10. Remote ID Relay

The Conduit includes a BLE scanner that detects nearby aircraft broadcasting ASTM F3411-22a Remote ID signals. Detected aircraft appear in the dashboard telemetry under the Nearby Aircraft section.

How It Works

• The BLE scanner runs continuously in the background (3-second scan interval)
• Detects Broadcast Remote ID messages over Bluetooth Low Energy
• Extracts UAS ID, position, altitude, speed, heading, and aircraft type
• Reports signal strength (RSSI) as a proxy for distance
• Tracks up to 8 simultaneous aircraft
• Entries expire after 30 seconds with no advertisement

Reported Data

11. MAVLink Relay Security

The SkyRelay cloud assigns each Conduit a unique UDP port (range 14550–14649) at device provisioning. Your ground control station (Mission Planner, QGroundControl) connects to this dedicated port to send and receive MAVLink data. Because this port accepts unauthenticated UDP packets, it is important to protect it from unauthorized access.

Threat: MAVLink Command Injection

MAVLink v1 and v2 (unsigned) do not authenticate the sender. Anyone who can reach your relay port could inject commands — arm, disarm, change mode, or navigate the aircraft. The following methods protect against this.

How to Protect Your Relay

1. Don't Share Your Connection Details

Your relay server address and UDP port number are unique to your drone. Treat them like a password.

• Do not post your relay address or port number publicly
• Only share connection details with authorized GCS operators
• Monitor the SkyRelay dashboard for unexpected connection activity

2. Enable MAVLink 2 Message Signing

MAVLink 2 supports HMAC-SHA256 message signing. When enabled, each message includes a cryptographic signature that the receiver verifies. Unsigned or incorrectly signed messages are rejected by the flight controller.

• Configure a shared signing key on both the flight controller and ground station
• ArduPilot: configure signing via MAVLink console or GCS (Mission Planner: Setup → MAVLink Signing)
• QGroundControl: Application Settings → MAVLink → Signing
• The Conduit relay passes signed messages transparently — signatures are end-to-end between FC and GCS
• Even if an attacker reaches your port, injected commands are rejected because they lack a valid signature

3. SkyRelay Guard VPN — Complete Protection

For the highest level of security, enable SkyRelay Guard. Guard creates an encrypted WireGuard VPN tunnel between your ground station and the SkyRelay cloud, making your relay port completely invisible to the public internet.

• Your relay port is only accessible from inside the VPN — no public exposure
• All MAVLink traffic is encrypted end-to-end between your GCS and the relay server
• Simple setup: install the WireGuard client on your GCS and import the config from your SkyRelay dashboard
• Works with any GCS (Mission Planner, QGroundControl, MAVProxy) — no changes to the GCS software
• Combines with MAVLink 2 signing for defense in depth

12. Troubleshooting

13. Specifications

Hardware

Electrical

Communication

Certifications