I may be doing some work involving a custom U-Boot, and I’m concerned with bricking the board, so I wanted to try “force recovery” mode before I did that.
I intend to use a Raspberry Pi for the host end of this connection.
When I jumper the recovery pins and then reset the Nano, I see this on the raspberry pi:
ubuntu@wrkpi:~$ sudo dmesg -c
[21709.178961] usb 1-1.2: new high-speed USB device number 91 using dwc_otg
[21709.280035] usb 1-1.2: New USB device found, idVendor=0955, idProduct=7f21, bcdDevice= 1.02
[21709.280057] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[21709.280071] usb 1-1.2: Product: APX
[21709.280086] usb 1-1.2: Manufacturer: NVIDIA Corp.
At this point, there is a new device:/dev/bus/usb/001/091
Can I connect to that with microcom? am I supposed to connect in some other way? If microcom, what speed do I choose? Parity?
I haven’t been able to get anything meaningful out of the USB connection.
Thank you
FYI, flash through JetPack or SDK Manager is just a GUI front end to what is known as the “driver package”, and the driver package runs on a desktop PC architecture.
Recovery mode does not actually alter the Nano. What this does is put the Nano into a sort of mini environment whereby it becomes a custom USB device. That device is understood only by the driver package. An RPi will be unable to flash, and the Jetson is not bulk storage when in recovery mode. What you are demonstrating is that the Nano made its way to recovery mode, and that the driver package could in theory work using that mini environment. Without the flash software running on a desktop PC this is just an exercise to show the unit functions as intended.
Serial console is a different story, and does not work in recovery mode (this does have some useful output in recovery mode, but it isn’t the usual interactive console). For an actual serial console, see:
https://www.jetsonhacks.com/2019/04/19/jetson-nano-serial-console/
(115200 8N1 settings)
FYI, flashing bootloader content which fails will not brick the unit…the unit will still be able to go into recovery mode and flashed again with valid content.