Raspberry Pi 5 USB-Gadget for hamradio and programming

The Swiss Army Knife for Ham Radio & Coding on iPad

My heart beats digital. For over 35 years, I’ve been an entrepreneur, but my passion for technology goes much deeper. Whether as a licensed radio amateur (73 de DL1GKK!) or while coding.

My focus in everything I do is on efficiency and minimalism. That is exactly why I choose not to use an additional Mac; iPhone and iPad are completely sufficient for my daily workflow. A Windows PC is simply not an alternative for me for many reasons. If I were to start all over again today, probably I would likely go all-in on Linux from the very beginning. But i like the great hardware from Apple. However, anyone who has tried to run specialized Ham Radio software or native Linux development on iOS or iPadOS inevitably hits a wall.

Apple heavily restricts the USB-C interface of these devices, and the available apps are often just a shadow of what is possible under Linux. Whether it’s digital modes like VARA (via Wine), WSJT-X, or complex compilers – everything runs on the Raspberry Pi. Until now, getting there was a rocky road: configuring the Pi as a hotspot, using a smartphone as a bridge… more often than not, it failed due to unstable Wi-Fi connections in the field. Headless troubleshooting without a monitor? A nightmare for any portable radio operation.

The Solution: The iPad as the Terminal, the Pi 5 as the Powerhouse

I have found the perfect solution to tear down that wall: the Raspberry Pi 5 in USB Gadget Mode. A single, high-quality USB-C data cable connects the iPad directly to the Pi. The result? The iPad provides the power, and the Pi provides a stable Ethernet signal over the cable and do all the great ham radio stuff.

It is the ultimate all-rounder:

• On the go: True “Plug & Play” on the iPad. Full access via VNC or SSH – without unstable Wi-Fi.
• At home: Simply plug it into a power supply and use it as a standalone server via LAN or Wi-Fi.
• Universal: Works on any modern computer with a high-performance USB-C port that can deliver enough power.

Maintenance Philosophy: “Never Change a Running System”

In a complex environment like this—with Wine, Vara HF, and custom Gadget scripts—a single automatic update can break your entire workflow. Operating a “Pi-Go” is like operating a specialized piece of machinery: stability is more important than having the latest version of every minor background tool.

My advice: Turn off the automatic update notifications in your taskbar. Only perform manual updates (sudo apt update && sudo apt upgrade) when you have the time to troubleshoot potential issues. Rule of thumb: No updates shortly before a field day or a DX-pedition!

The Bookworm 32bit OS Setup (for ham radio)

Note: Operating on a 32-bit OS (essential for Wine/Vara stability) with the specific Pi 5 kernel requires a few special tweaks. Here is my field-tested, step-by-step guide so you can skip the troubleshooting and get straight to work.

Step 1: Prepare the Hardware Driver

We need to tell the Pi 5 that its USB-C port should act as a network interface rather than just a power input.

sudo nano /boot/firmware/config.txt

• Find the line otg_mode=1 and comment it out with a #: # otg_mode=1
• Find dtoverlay=dwc2,dr_mode=host and comment it out as well: # dtoverlay=dwc2,dr_mode=host
• Ensure kernel=kernel8.img (required for Wine/Vara) remains active.
• Add the following lines at the very end of the file under the [all] section:

[all]
dtoverlay=dwc2,dr_mode=peripheral

Step 2: Load Kernel Modules at Boot

Next, we enable the network emulation within the operating system.

sudo nano /boot/firmware/cmdline.txt

Go to the end of the first line, add a space, and append the following (must stay on one single line!):

modules-load=dwc2,g_ether

Step 3: Create the Gadget Script

This script defines the Pi’s identity (e.g., my callsign DL1GKK) so the iPad recognizes it correctly.

sudo nano /usr/local/bin/usb-gadget.sh

Paste the following code block entirely:

#!/bin/bash
modprobe libcomposite 2>/dev/null
modprobe dwc2 2>/dev/null
mount -t configfs none /sys/kernel/config/ 2>/dev/null
cd /sys/kernel/config/usb_gadget/
mkdir -p g1 && cd g1
echo 0x1d6b > idVendor
echo 0x0104 > idProduct
echo 0x0100 > bcdDevice
echo 0x0200 > bcdUSB
mkdir -p strings/0x409
echo "fedcba9876543210" > strings/0x409/serialnumber
echo "DL1GKK" > strings/0x409/manufacturer
echo "Pi5 Gadget" > strings/0x409/product
mkdir -p configs/c.1/strings/0x409
echo "Config 1: ECM network" > configs/c.1/strings/0x409/configuration
echo 250 > configs/c.1/bmAttributes
echo 500 > configs/c.1/MaxPower
mkdir -p functions/ecm.usb0
echo "00:22:82:ff:ff:01" > functions/ecm.usb0/host_addr
echo "00:22:82:ff:ff:02" > functions/ecm.usb0/dev_addr
ln -s functions/ecm.usb0 configs/c.1/
UDC_NAME=$(ls /sys/class/udc | head -n 1)
echo "$UDC_NAME" > UDC

Make the script executable:

sudo chmod +x /usr/local/bin/usb-gadget.sh

Step 4: Automation & Hardware Switch (CRITICAL!)

To ensure the script runs on every boot, we use rc.local.

sudo nano /etc/rc.local

Insert the following (including the Shebang if the file is empty):

#!/bin/bash
/usr/local/bin/usb-gadget.sh &
exit 0

Make rc.local executable:

sudo chmod +x /etc/rc.local

IMPORTANT: A simple reboot is not enough at this stage! Shut down the Pi completely (sudo halt). Disconnect the power supply. Now, connect the Pi directly to your iPad using a high-quality USB-C data cable. The Pi will now boot using the iPad’s power.

Step 5: First-Time Network Initialization

Once the Pi has booted up via the iPad (you should see “Ethernet” appear in your iPad settings), run these commands once on the Pi to wake up the connection:

sudo ip link set usb0 up
sudo nmcli device set usb0 managed yes
sudo nmcli con add type ethernet con-name usb-ipad ifname usb0 ip4 10.42.0.1/24 ipv4.route-metric 1000
sudo nmcli con mod usb-ipad connection.zone trusted
sudo nmcli con up usb-ipad

Step 6: iPad Settings

On your iPad, navigate to Settings > Ethernet and tap the connection:

• Configure IPv4: Manual
• IP Address: 10.42.0.10
• Subnet Mask: 255.255.255.0
• Router: Leave it blank

Note: The reason we don’t enter anything under “Router” is that we want to continue using the iPad’s Wi-Fi or 5G connection to access the internet. Once the PI5 is connected to the internet (via Wi-Fi, Ethernet, or a smartphone hotspot), you can enter 10.42.0.1.

The Bookworm 64bit OS Setup (Not recommended for ham radio)

Phase 1: The USB-C Gadget (The Data Link)

Now we “weld” the virtual network card so the USB-C cable handles both power and data.

1.1 Enable Kernel Modules

echo "dtoverlay=dwc2" | sudo tee -a /boot/firmware/config.txt
sudo nano /boot/firmware/cmdline.txt

Go to the end of the line (don’t delete anything!). After a space, add exactly this: modules-load=dwc2,g_ether

1.2 Create the Network Profile

sudo nmcli con add type ethernet con-name usb-gadget ifname usb0 save yes autoconnect yes 802-3-ethernet.cloned-mac-address 12:34:56:78:9a:bc ipv4.method shared ipv4.addresses 10.42.0.1/24

1.3 Permanent Assignment (systemd)

To ensure the IP 10.42.0.1 is ready every time you plug in:

sudo nano /etc/systemd/network/10-usb0.network

Paste this content:

[Match]
Name=usb0

[Network]
Address=10.42.0.1/24

1.4 Hardware Rule (udev)

sudo nano /etc/udev/rules.d/99-usb-gadget.rules

Paste this content:

ACTION=="add", SUBSYSTEM=="net", KERNEL=="usb0", RUN+="/usr/sbin/ip link set usb0 up"

Activate the service: sudo systemctl enable systemd-networkd

Phase 2: The Shutdown Ritual & iPad Connect

2.1 The Professional Shutdown

1. Type in terminal: sudo shutdown -h now.
2. Patience: Wait for the monitor signal to cut off.
3. LED Check: Watch the red LED on the Pi. Wait for 1 to 2 minutes until the green flashing (SD card activity) stops completely. Once only the red LED stays solid, unplug the power and monitor.

2.2 Connecting to the iPad

1. Connect the Pi 5 to the iPad via a USB-C cable. It will boot using the iPad’s power.
2. On your iPad, go to Settings -> Ethernet (appears after ~30s).
3. Tap the connection and select Configure IP -> Manual:
   • IP Address: 10.42.0.10
   • Subnet Mask: 255.255.255.0
   • Router: leave blank
4. Open your VNC app (RealVNC or Jump Desktop) and connect to 10.42.0.1. It works also great with SSH.