How to get USB OTG port to work in Device mode?

Technical Support
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@g4b42 has worked this out for me - you will need to modify a few files and rebuild the kernel - but its straight forward to do using fenix. How I did it yesterday:

  1. download fenix and pick the options that you want, then let it run until it has downloaded linux, the ctrl-c to halt the build (when it starts building linux is when i stopped it)

  2. in the linux directory apply the following changes
    => https://github.com/g4bwy/khadas-linux/commit/d9a6fe9e97bb1d2c55ed918f9fd7632d0d7dbb08
    => https://github.com/g4bwy/khadas-linux/commit/564439f83cfe63fef675991cdb94512eee14df04
    => https://github.com/g4bwy/khadas-linux/commit/d8b8378ed54d7572fa77c2f4e168a7d94b914bf2

  3. start the fenix build again and press enter when asked if you want to proceed with the modified files

  4. burn the resulting image to your VIM3

  5. create a script called usb.sh in /root/ with the following contents and make it executable. Note that each MAC address has to be unique - so if creating multiple devices to put on the same hub then you need to change these per device.
    #!/bin/sh
    [ ! -d “/config” ] && mkdir /config
    mount -t configfs none /config
    mkdir /config/usb_gadget/g1
    echo 0x18d1 > /config/usb_gadget/g1/idVendor
    echo 0x4ee1 > /config/usb_gadget/g1/idProduct
    mkdir /config/usb_gadget/g1/strings/0x409
    echo 12345678 > /config/usb_gadget/g1/strings/0x409/serialnumber
    echo Dummy > /config/usb_gadget/g1/strings/0x409/manufacturer
    echo Demo > /config/usb_gadget/g1/strings/0x409/product
    mkdir /config/usb_gadget/g1/configs/c.1
    mkdir /config/usb_gadget/g1/configs/c.1/strings/0x409
    echo “Conf 1” > /config/usb_gadget/g1/configs/c.1/strings/0x409/configuration
    echo 120 > /config/usb_gadget/g1/configs/c.1/MaxPower
    mkdir /config/usb_gadget/g1/functions/eem.f0
    echo “66:77:88:99:aa:00” > /config/usb_gadget/g1/functions/eem.f0/host_addr
    echo “00:11:22:33:44:00” > /config/usb_gadget/g1/functions/eem.f0/dev_addr
    ln -s /config/usb_gadget/g1/functions/eem.f0 /config/usb_gadget/g1/configs/c.1/$
    echo ff400000.dwc2_a > /config/usb_gadget/g1/UDC

  6. edit /etc/network/interfaces and add the following for usb0 - assumes an available DHCP server for where the device is being plugged into, can also set for a static IP address if required
    auto usb0
    iface usb0 inet dhcp
    pre-up /root/usb.sh

  7. reboot and use your device with USB ethernet - a useful check to make sure its working is to use ip a or ifconfig to make sure that a) usb0 shows up as a device and b) it has an IP address assigned to it

  8. ask Khadas nicely to put this config changes into the standard kernel build to save some steps :slight_smile:

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