3. Load Root Partition From SSD
It is easier to troubleshoot problems with the device if you connect to the serial port. For example this lets you get to the U-Boot command prompt.
You will need a command line utility to connect to the serial port. The standard is minicom. I use BootTerm:
git clone https://github.com/wtarreau/bootterm
cd bootterm
make
sudo make install
There are two USB C ports on the back of the device, one labelled USB-CPD for power, the other labelled DEBUG for the serial port. Connect a USB cable from the serial port on the R6C to a USB port on your laptop.
On your laptop, do:
sudo bt -b 1500000
Now power up the NanoPi. The first time I try this it does not work. On the laptop I run dmesg and it says:
[70743.937494] usb 1-11: new full-speed USB device number 26 using xhci_hcd
[70744.087234] usb 1-11: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.64
[70744.087239] usb 1-11: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[70744.087240] usb 1-11: Product: USB Serial
[70744.089068] ch341 1-11:1.0: ch341-uart converter detected
[70744.089565] usb 1-11: ch341-uart converter now attached to ttyUSB0
[70746.346638] usb 1-11: usbfs: interface 0 claimed by ch341 while 'brltty' sets config #1
[70746.347190] ch341-uart ttyUSB0: ch341-uart converter now disconnected from ttyUSB0
[70746.347204] ch341 1-11:1.0: device disconnected
[70818.398641] usb 1-11: USB disconnect, device number 26
The R6C appears on device ttyUSB0, but some process called brltty grabs the connection before BootTerm can. So I disable brltty:
erik@laptop:~$ sudo systemctl stop brltty-udev.service
erik@laptop:~$ sudo systemctl mask brltty-udev.service
Created symlink /etc/systemd/system/brltty-udev.service → /dev/null.
erik@laptop:~$ sudo systemctl stop brltty.service
erik@laptop:~$ sudo systemctl disable brltty.service
Then I restart everything and now BootTerm shows me the output of the serial port from the NanoPi.