Is an USB serial connection needed to boot into Linux as the QSG suggests?
Also, can I flash the soon-to-be-released Debian image to NVMe and boot from NVMe?
If you want to interact with the console, yes.
It’s not like OpenBIOS and netboot and all that are configurable over a USB keyboard and display on a monitor. You also have to install the OS somehow. (Yes, DietPi has this figured out to install totally headless… But I don’t think we’re there yet.
Maybe you can configure your OS to bring up networking and ssh into it, just like you can just not turn on your monitor today, but boot problems are going to be hard to diagnose.
As a practical matter, you need serial. If you have native serial or a VT100, it doesn’t HAVE to be a. USB/serial adapter (maybe it’s another SBC…) But if you have to ask, the answer is Yes.
… Unless there have been major check-ins in the last few weeks that I haven’t seen, which might happen. Devs may be queueing up surprises for launch and the RISC-V show next week.
I plan to develop via SSH. I was just wondering if the Linux kernel starts automatically. The QSG suggested that serial is needed to kickstart the boot process (i.e. u-boot does not start the kernel automatically). Is that true?
Do you know if NVMe boot works such that I can flash the soon-to-be-released Debian image to NVMe and boot from NVMe?
The VF2 boot mode supports qspi, sd, uart, emmc, does not support booting directly from NVMe, there is a plan to boot from qspi+nvme, it is not supported yet.
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Thanks, @julie. Follow up question: do I need a serial console / USB serial adapter to boot VF2 into Linux as the docs suggest?
If you use Debian with a desktop environment, you don’t have to, but we recommend that you prepare a USB to Serial Converter, the bootloader is stored inside the SPI flash ,there may be situations when you accidentally emptied the flash or if the flash is damaged on your visionfive 2，you can recovery the bootloader though it.
May the advantages of VF2 will be wiped out if it couldn’t be able to boot from NVME SSD. 
Hi Julie, can you please link to the Debian image? It is referenced by name in many places but with no link in sight. I visited the Github and downloaded sdcard.img, it does not contain Debian (nor does it boot to X, and the weston script segfaults).
Also, I have to boot using USB to TTL right now because the HDMI does nothing.
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The Debian OS is doing some optimization, and we will release it soon.
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Same inquiry as @larryw3i: for the Debian image, is USB to TTL needed?
Also, can anyone recommend a USB-TTL cable?
Any USB debug UART that supports 3.3V TTL voltage should work.
In fact in a pinch if you have an old Raspberry Pi, it supports 3.3 volt TTL, so if you know what you are doing you could use that for a debug UART.
/dev/ttyS0
VisionFive2 Pin 6: Ground
VisionFive2 Pin 8: UART0 TX (AKA GPIO 5)
VisionFive2 Pin 10: UART0 RX (AKA GPIO 6)
probably: /dev/serial1 or /dev/ttyAMA0
might be: /dev/serial0 or /dev/ttyS0
Raspberry Pi Pin 6: Ground
Raspberry Pi Pin 8: UART0, TXD0 (AKA GPIO 14)
Raspberry Pi Pin 10: UART0, RXD0 (AKA GPIO 15)
So you would wire RPi pin 6 to VF2 pin 6 (A common ground between the boards), RPi pin 8 to VF2 pin 10 (RPi TX to VF2 RX), RPi pin 10 to VF2 pin 8 (RPi RX to VF2 TX).
I’ve used the ‘DSD TECH SH-U09C5’ (Got it on a local Amazon)
It works fine. Just mind the R and T cables have to be crossed when plugging to the board.
I’ve bought it with a 2m USB cable extender to keep the board neatly away from the dev machines.
Boot & login works with setup:
Switch_0 high
Switch_1 low
Build from sdk and flashed to microSDcard (not TF)
Plug usb to serial on UART gnd/TX/RX (with 2303HXA) on MacOs
Alim on USB connector
In my experience, no. I can SSH into Linux running on the board just fine without serial or HDMI. Serial is really only needed for debugging and recovery and things of that nature. You can use sdcard.img to update the uboot and SPL via SSH/SCP, then boot it off of the release 69 (or latest) Debian just fine from there on.
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