PX4 -> QGC connection through USB for VOXL2

Alex Kushleyev

@bendraper , I will ask around.

bendraper

@Alex-Kushleyev So I can see a gadget functionality called gsi.rndis (I'd expect something called rndis.0 or something but maybe that is irrelevant) but when I change the line in /sbin/usb/compositions/901D to use gsi.rndis instead of ncm.0, my network interface on windows disappears and I can no longer ADB. I'd imagine there's something at the kernal level that doesn't like that but I'm out of my wheelhouse there. Setting it back to ncm.0 returns to the previous state but still cannot ping. Wireshark doesn't even see anything happening over that interface

Zachary Lowell 0

Hi All - gonna spend a bit of time looking into this today so I can get some context on the problem.

Zach

qt

This post is deleted!

qt

This post is deleted!

qt

@Alex-Kushleyev
That's not perfect but I created a shell script based on https://docs.modalai.com/qgc-via-adb/ for the drone configuraiton.
For my PC configuration, I created an udev rule to force an interface name since usb0 is renamed in "enx******". My udev rule can only work with my drone (I think). To define IP address, I add a conf file in /etc/systemd/network/
I have only tested on my linux and it works perfectly :

#!/usr/bin/env bash
set -euo pipefail

# See ModalAI doc : https://docs.modalai.com/qgc-via-adb/

UDEV_RULE_DRONE="/etc/udev/rules.d/80-usb-ncm.rules"
UDEV_RULE_PC="/etc/udev/rules.d/99-voxl-usb-ncm.rules"
SYSTEMD_CONF_PC="/etc/systemd/network/10-voxl0.network"

USB_COMP_QUALCOM="/sbin/usb/compositions/901D"

# Network configuration
USB_IFACE="usb0"
USB_NET="192.168.7.0/24"
PC_IP="192.168.7.1"
DRONE_IP="192.168.7.2"
NM_CONN_NAME="voxl-usb-ncm"

show_help() {
    echo "Usage: $0 [--pc] [--drone] [--uninstall]"
    echo
    echo "Enable USB NCM networking for ModalAI VOXL / Starling 2 Max"
    echo
    echo "Options:"
    echo "  --pc         Configure host PC only"
    echo "  --drone      Configure drone via adb only"
    echo "  --uninstall  Remove configuration"
    echo "  --help       Show this help"
    echo
    echo "Defaults: if neither --pc nor --drone is provided, both are processed."
}

do_pc_install() {
    echo "[INFO][PC] Installing udev rule for VOXL USB NCM"

    cat > "$UDEV_RULE_PC" <<EOF
SUBSYSTEM=="net", ACTION=="add", ATTRS{idVendor}=="05c6", ATTRS{idProduct}=="901d", ATTRS{serial}=="890d035c", NAME="voxl0"
EOF

    echo "[INFO][PC] Creating systemd-networkd config for voxl0"

    cat > "$SYSTEMD_CONF_PC" <<EOF
[Match]
Name=voxl0

[Network]
Address=${PC_IP}/24
LinkLocalAddressing=no
IPv6AcceptRA=no
EOF

    echo "[INFO][PC] Reloading udev rules"
    udevadm control --reload-rules
    udevadm trigger

    echo "[INFO][PC] Restarting systemd-networkd"
    systemctl restart systemd-networkd

    echo "[INFO][PC] PC installation complete"
}

do_pc_uninstall() {
    echo "[INFO][PC] Removing PC configuration"

    if [ -f "$UDEV_RULE_PC" ]; then
      rm -f "$UDEV_RULE_PC"
      echo "[INFO][PC] Removed udev rule"
    fi

    if [ -f "$SYSTEMD_CONF_PC" ]; then
      rm -f "$SYSTEMD_CONF_PC"
      echo "[INFO][PC] Removed systemd-networkd config"
    fi

    echo "[INFO][PC] Reloading udev rules"
    udevadm control --reload-rules
    udevadm trigger

    echo "[INFO][PC] Restarting systemd-networkd"
    systemctl restart systemd-networkd

    echo "[INFO][PC] PC uninstallation complete"
}

do_drone_install() {
    echo "[INFO][DRONE] Enabling USB NCM networking on VOXL via adb"

    adb root
    adb remount

    echo "[INFO][DRONE] Updating USB composition in Qualcomm script \
$USB_COMP_QUALCOM configure the usb gadget with \
the addition of the function NCM"
    echo "[INFO][DRONE] In $USB_COMP_QUALCOM, \
add the line 'ln -s functions/ncm.0 configs/c.1/f3 2>/dev/null | true' \
just after the line 'ln -s functions/ffs.adb configs/c.1/f2'"
    
    adb shell "sed -i '/ln -s functions\\/ffs.adb configs\\/c.1\\/f2/a \
    \\        ln -s functions\\/ncm.0 configs\\/c.1\\/f3 2>\\/dev\\/null | true' \
    $USB_COMP_QUALCOM"

    echo "[INFO][DRONE] Creating udev rule $UDEV_RULE_DRONE for usb0 with IP ${DRONE_IP}"
    
    adb shell "cat << 'EOF' > $UDEV_RULE_DRONE
ACTION==\"add\", SUBSYSTEM==\"net\", KERNEL==\"usb0\", \
RUN+=\"/bin/sh -c 'sleep 2; /sbin/ifconfig usb0 ${DRONE_IP} netmask 255.255.255.0 up'\"
EOF"

    echo "[INFO][DRONE] NCM enabled — reboot required"
}

do_drone_uninstall() {
    echo "[INFO][DRONE] Removing NCM configuration"

    adb root
    adb remount

    echo "[INFO][DRONE] Removing udev rule $UDEV_RULE_DRONE"
    adb shell "rm -f $UDEV_RULE_DRONE || true"

    echo "[INFO][DRONE] Reverting USB composition (901D)"
    adb shell "
    sed -i '/ln -s functions\\/ncm.0 configs\\/c.1\\/f3/d' \
    $USB_COMP_QUALCOM
    "

    echo "[INFO][DRONE] USB NCM configuration removed"
    echo "[INFO][DRONE] Reboot required to fully apply changes"
}


# Arg parsing
TARGET_PC=false
TARGET_DRONE=false
DO_UNINSTALL=false

for arg in "$@"; do
  case "$arg" in
    --help) show_help; exit 0 ;;
    --pc) TARGET_PC=true ;;
    --drone) TARGET_DRONE=true ;;
    --uninstall) DO_UNINSTALL=true ;;
    *)
      echo "[ERROR] Unknown argument: $arg";
      show_help;
      exit 1 ;;
  esac
done

# Default to both if none selected
if ! $TARGET_PC && ! $TARGET_DRONE; then
  TARGET_PC=true
  TARGET_DRONE=true
fi

# Execute
if $DO_UNINSTALL; then
  $TARGET_PC && do_pc_uninstall
  $TARGET_DRONE && do_drone_uninstall
else
  $TARGET_PC && do_pc_install
  $TARGET_DRONE && do_drone_install
fi

echo "[INFO] All done."
``

bendraper

@Zachary-Lowell-0 Hey Zach did you discover anything in this effort? I played around with recompiling the kernel to include the CONFIG_USB_CONFIGFS_RNDIS=y flag and confirmed it took on my Voxl 2 Mini, and can see the existence of a new rndis.rndis function in the usb gadget functions directory, but when I try to reconfigure the 901D config file, I end up just breaking the USB port entirely.

Zachary Lowell 0

@qt said in PX4 -> QGC connection through USB for VOXL2:

name

@bendraper I kind of redid exactly what you described above and ran into very similar issue in the sense that it basically rocked my usb-c port. All this to say, I think we should choose a different route - is it possible instead to route the packets via adb over the USB-C port instead to basically get the same result? Point the software to the serial connection and leverage ADB to pull the packets that are forwarded? Basically creating our own sudo rndis connection almost.

Zach

bendraper

@Zachary-Lowell-0 This would probably work but for my use case I cannot guarantee ADB being an option unfortunately.

Alex Kushleyev

@bendraper , have you considered running a docker container (VM) on your Windows machine with a minimal Linux kernel that would use the Linux drivers for NCM and create the proper network connection between VOXL2 and Linux container. Then you could potentially set up the routing table in Windows so that it can access the device via the Linux container and linux container may need to have some networking magic down as well to pass through the communication?

Alex