NanoKVM Lite - External Power

Question

NanoKVM Lite - External Power

Opened this issue 24 days ago · 10 comments

Hello,
I don't understand if I can provide 5V to the NanoKVM Lite through pins and not from the USB C port.

The problem is that I'm trying to manage a SBC and when I reboot the SBC, the NanoKVM Lite loses the power and I don't see the initial steps in the boot process.

Thank you.
Regards,
Marco

Answer 1 · 2024-12-03T23:56:19.000Z

There are pads to the back of USB Type-C port which can be used to power up the board:

Two of the pin headers are also on 5V rail, but those, alongside GPIO A14 and the 3V3 pins, are being occupied to fix the HDMI board in place, thus unusable.

Answer 2 · 2024-12-04T10:17:41.000Z

@x-magic is there a risk that this will inject the power into the PC via the USB-C cable?

Answer 3 · 2024-12-04T11:04:41.000Z

is there a risk that this will inject the power into the PC via the USB-C cable?

It absolutely will 🤣

I personally won’t rely on NanoKVM Lite for POST stage as I found the way it handles HID causing 2/3 of my devices not to recognise keyboard on boot. So it doesn’t really matter if the board is powered externally or not.

Answer 4 · 2024-12-04T13:33:45.000Z

so I don't think the proposed solution is valid @x-magic
Is there any protection we can apply?
What's the purpose of using NanoKVM lite if you cannot access the bootmenu of a Linux box and select the right Kernel or access the BIOS?

Answer 5 · 2024-12-04T21:34:29.000Z

@marino-mrc just FYI - I'm not affiliated with Sipeed and just an end user like you.

I'm saying that because I have gone through their documentation before purchasing and having a realistic expectation of pros and cons. NanoKVM full version (final version, not beta) has proper backfeed-protected aux power.

According to the official FAQ, you can decouple the USB VCC and board VCC by removing the 0R on the 5V pad next to the microSD card slot, and power on the board separately from the USB host.

Answer 6 · 2024-12-05T09:17:58.000Z

It's not clear to me how to proceed after removing the 0 ohm resistor. Can I use the V and G pins under the USB-C connector to power up the board and connect the USB-C to my SBC?
Can you give me a link to the documentation where I can get more details on this procedure?

Answer 7 · 2024-12-05T09:22:00.000Z

The official documentation is linked on this very repo's README file.

I can't tell how 0R pad works exactly as I can't find this thing on the schematics, or maybe I'm just suck at reading schematics 🙃

If you want more information, it's worth it to at one of the repo maintainers.

Answer 8 · 2024-12-17T23:44:16.000Z

Are there any updates on this? I'd like to power my Lite from external power but I don't need the atx controls nor the screen

EDIT:

From what I am gathering from the schematics ( I am a n00b) They seem to be sending power to the pin GPIOA24 witch is GPIO_DET_POWERLED and then the ground to ground through a 1KΩ resistor but I might be mistaken.

Some better schematics with traces are needed

Answer 9 · 2024-12-18T09:21:00.000Z

Hello,
I found some things (but I'm super busy, therefore correct me if I'm wrong):

The "real" schematics are here: https://cn.dl.sipeed.com/shareURL/LICHEE/LicheeRV_Nano
You can remove the 0 Ohm resistor from the circuit and then power the board using VSYS and GND. Don't use VBUS. Unfortunately, you have to solder a short cable on the VSYS pin because the connector is occupied by the HDMI hat.

It's quite simple TBH but again, I'm working on a lot of things and I couldn't verify this on a real NanoKVM Lite board.

Regards,
Marco

Answer 10 · 2024-12-18T16:25:37.000Z

I did look at the schematics, but without any pcb with traces I can't understand what is going on