2. System and network

The result of this step is a Pi with realtime scheduling and a separate wired link to each robot. No robot motion is needed here.

Install a 64-bit realtime system

A documented route is Ubuntu Server 24.04 LTS for Raspberry Pi + the Raspberry Pi real-time kernel. Write the image to your microSD with Raspberry Pi Imager using the Ubuntu Raspberry Pi image. Set up your account, SSH, and an uplink on the Pi’s built-in Ethernet or Wi-Fi.

The kernel route below requires an Ubuntu Pro entitlement. Follow Canonical’s enablement guide:

sudo apt update
sudo apt install ubuntu-advantage-tools pciutils ethtool
sudo pro attach
sudo pro enable realtime-kernel --variant=raspi
sudo reboot

Use --variant=raspi, not the generic real-time kernel. After reconnecting:

uname -m                    # aarch64
cat /sys/kernel/realtime     # 1

Already have a Pi-compatible PREEMPT_RT image? Keep it and check the same outputs. An ordinary Raspberry Pi OS install is not automatically a realtime system; custom kernel builds are an advanced alternative, not required by this guide.

Enable PCIe and identify the Intel ports

For the P02, edit /boot/firmware/config.txt and ensure this line is active under [all]:

dtparam=pciex1

Reboot. Keep the Pi’s default PCIe Gen 2 speed; no Gen 3 override is needed here. See Raspberry Pi’s PCIe instructions.

lspci -nnk
ip -br link

Find the Intel I350 functions in lspci; the driver in use should be igb. List interface names with ip -br link, then use ethtool -i <interface> to match each interface’s bus-info to its PCI address in lspci (replace the placeholder). If no card is listed, power down and recheck seating, ribbon orientation, and adapter power. If no driver is bound, resolve the kernel’s igb support before continuing.

Plug in one cable at a time and inspect ip -br link / ethtool <interface> to map the physical L and R ports. Write down which interface belongs to each arm. The built-in Ethernet is the uplink and is not one of these Intel interfaces.

For one arm without the Intel card, use the built-in Ethernet as LEFT_INTERFACE below, omit the right interface, and use Wi-Fi for the laptop uplink. Skip the PCIe checks.

Give each arm its own subnet

Example addresses below are a setup plan, not values discovered on your robot. Use subnets that do not overlap your uplink, VPN, or another interface. Confirm the robot-side address in its network configuration before applying the Pi-side settings.

For two arms, configure the second robot for its separate subnet through the robot’s network settings. Setting the Pi to 172.16.2.1 does not change the robot’s address. Do not put two default 172.16.0.2 robots on separate interfaces in the same routing table and expect automatic selection. Start with one arm if both still have the same address.

On Ubuntu Server using Netplan/networkd, add the following to /etc/netplan/60-franka.yaml. Replace LEFT_INTERFACE and RIGHT_INTERFACE with the actual Intel interface names. Remove the right entry for one arm. Keep your existing uplink config; if another Netplan file already configures these Intel ports, reconcile it first.

network:
  version: 2
  ethernets:
    LEFT_INTERFACE:
      renderer: networkd
      dhcp4: false
      dhcp6: false
      addresses: [172.16.0.1/24]
      optional: true
    RIGHT_INTERFACE:
      renderer: networkd
      dhcp4: false
      dhcp6: false
      addresses: [172.16.2.1/24]
      optional: true

No default gateway or DNS belongs on the robot links. Those stay on the uplink. Check and try the configuration with rollback rather than replacing your SSH connection:

sudo chmod 600 /etc/netplan/60-franka.yaml
sudo netplan generate
sudo netplan try
ip route get 172.16.0.2
ip route get 172.16.2.2       # only with a second arm

Each route should show the intended Intel interface and matching Pi source address. Netplan’s static-address guide explains the configuration. A NetworkManager-managed system needs its corresponding connection profiles instead.

Allow realtime scheduling

Create a group and add your login account:

sudo groupadd -f realtime
sudo usermod -aG realtime "$USER"

Create /etc/security/limits.d/99-franka-realtime.conf with:

@realtime - rtprio 99
@realtime - memlock unlimited

Log out and back in, then check ulimit -r reports 99. The service in the next step also sets these limits. See the realtime machine for details.

Before moving on

• cat /sys/kernel/realtime reports 1 and ulimit -r reports 99.
• Each Intel port is identified, and routing selects the expected port for each robot.
• ping 172.16.0.2 works (and 172.16.2.2 for two arms).
• The laptop can still reach the Pi’s uplink address. This is the address used for Zenoh.

Ping verifies basic reachability, not 1 kHz timing. The later communication test moves the robot and must follow the robot’s motion prerequisites. Do not run it alongside an active node.