3.0 KiB
OTG
OTG (on-the-go) is a neat feature which allows you to connect to your system over ssh by just connection it to usb-c. Therefore you don't need any network cable, bluetooth or wifi connection. It's low power and reduces further risks of detection or hackers.
Update your system first
sudo apt update
sudo apt install rpi-eeprom
sudo apt full-upgrade
Change the /boot/config.txt and /boot/cmdline.txt files. You can edit them directly with nano: sudo nano /boot/config.txt and sudo nano /boot/cmdline.txt
/boot/config.txt:
# enable USB OTG
dtoverlay=dwc2
in /boot/cmdline.txt add directly after rootwait:
modules-load=dwc2,g_ether
After that we need to add:
libcompositeto/etc/modules(sudo nano /etc/modules)denyinterfaces usb0to/etc/dhcpcd.conf(sudo nano /etc/dhcpcd.conf)
We are ready to configure the network sharing, to do that you need to install and configure dnsmasq:
sudo apt install dnsmasq
And create /etc/dnsmasq.d/usb with the following content (sudo nano /etc/dnsmasq.d/usb):
interface=usb0
dhcp-range=10.55.0.2,10.55.0.6,255.255.255.248,1h
dhcp-option=3
leasefile-ro
Next to that we create /etc/network/interfaces.d/usb0 with the following content:
auto usb0
allow-hotplug usb0
iface usb0 inet static
address 10.55.0.1
netmask 255.255.255.248
Finally we create /root/usb.sh, a simple python script with the following lines of code:
#!/bin/bash
cd /sys/kernel/config/usb_gadget/
mkdir -p pi4
cd pi4
echo 0x1d6b > idVendor # Linux Foundation
echo 0x0104 > idProduct # Multifunction Composite Gadget
echo 0x0100 > bcdDevice # v1.0.0
echo 0x0200 > bcdUSB # USB2
echo 0xEF > bDeviceClass
echo 0x02 > bDeviceSubClass
echo 0x01 > bDeviceProtocol
mkdir -p strings/0x409
echo "fedcba9876543211" > strings/0x409/serialnumber
echo "Ben Hardill" > strings/0x409/manufacturer
echo "PI4 USB Device" > 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/MaxPower
# Add functions here
# see gadget configurations below
# End functions
mkdir -p functions/ecm.usb0
HOST="00:dc:c8:f7:75:14" # "HostPC"
SELF="00:dd:dc:eb:6d:a1" # "BadUSB"
echo $HOST > functions/ecm.usb0/host_addr
echo $SELF > functions/ecm.usb0/dev_addr
ln -s functions/ecm.usb0 configs/c.1/
udevadm settle -t 5 || :
ls /sys/class/udc > UDC
ifup usb0
service dnsmasq restart
This script need to be run every time the RPi is booted, to do that add /root/usb.sh to /etc/rc.local before exit 0 line.
With this setup the RPi will show up as a ethernet device with an IP address of 10.55.0.1 and will assign the device you plug it into an IP address via DHCP. This means you can just ssh to <username>@10.55.0.1 to start using it.