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USB Tether

Plug a USB-C data cable from the ground station to your Mac, Windows, or Android device. The SBC appears as a USB Ethernet adapter. No drivers to install on modern operating systems. Video latency drops to 40-70 ms because you skip the WiFi hop entirely. The Ground Agent still does the radio receive work. Your Mac or Windows laptop talks to the Ground Agent over USB Ethernet and receives standard IP streams.

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How it works

The Pi 4B USB-C port supports USB 2.0 OTG device mode. The agent configures a libcomposite USB gadget at boot that presents two Ethernet functions:
  • CDC-NCM (standards-compliant, native on macOS Sonoma+, Windows 11, Linux, Android 11+)
  • RNDIS (Microsoft proprietary, fallback for Windows 10)
Your laptop picks whichever it supports. You get a new network interface with a static IP.

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Platform support

macOS Sonoma and later. Plug the cable. System Settings shows a new “ADOS Ground Station” network interface. Open your browser and go to http://192.168.7.1:4000 or http://ground-station.local:4000. No driver install needed.macOS selects CDC-NCM automatically.

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What you can reach over USB tether

All the same endpoints as WiFi, but at 192.168.7.1 instead of 192.168.4.1:

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Why USB tether

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Throughput

More than enough for multiple video streams and telemetry. USB 3.0 is not needed at these rates.

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Power and cables

Many cheap USB-C cables are power-only and do not carry data. If your laptop does not detect a new network interface after plugging in, try a different cable. Look for cables explicitly labeled “data” or “USB 2.0/3.0 data capable.”
The Pi 4B USB-C port is both data and power. A laptop that provides USB-C power may back-power the Pi, but some laptops only provide 500 mA. The Pi under WiFi AP and radio load needs more than that. Brownouts cause instability. Recommended setup: Power the Ground Agent from its own wall adapter or USB-C power bank. Use a separate data-capable USB-C cable for the tether. This separates power from data and avoids brownout issues. For runtime sizing, see Power and Runtime.

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Combining USB tether with WiFi AP

You can use both at the same time. One client connects over USB tether for the lowest latency pilot view. Other clients connect over WiFi AP to observe. The agent serves both subnets simultaneously. The two subnets do not bridge by default. A client on 192.168.7.x (USB) cannot see clients on 192.168.4.x (WiFi) unless you enable uplink sharing in the network config.

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HTTPS caveat

Same as WiFi: if your browser loaded Mission Control from https://command.altnautica.com, it blocks http://192.168.7.1 connections. Use the local build at http://192.168.7.1:4000 or run Mission Control on your laptop at http://localhost:4000.

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Troubleshooting

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What is next