Y-Split - No Power?

[scottgrobinson]

Hello,

I've recently received two JetKVMs and they seem to power up when directly connecting to the PC with the included USB-A to USB-C cable. However... When using the Y-Split cable, I get nothing. Zilch...

I've confirmed I am using the power input on the Y-split, and not the data input, but I've tried both just to be sure I'm not crazy... I've tried various combinations:

• Power only connected to Y-split
• Data only connected to Y-split
• Data & power connected to Y-split

None of these power the unit. I've tried a variety of cables and a variety of charges - All cables and charges will charge a phone and power other deviecs fine without issue.

Thoughts? Where do I go next...?

[rmschooley]

Based on the bad experience of others, I have been scared of doing much testing with the cables. I have always just used the USB-A to USB-C cable while using my JetKVM. I should note that plugging the USB-C end of the cable to my JetKVM also works fine no matter which way the connector is plugged in.

HOWEVER...For better or for worse, I just tried plugging in my JetKVM to my phone charger which is a Samsung Super-Fast Charger that connects to a USB-C to USB-C Cable. I am able to plug this cable into my phone (S22+) and have it charge no matter what way the connector is plugged in. But...When I plug this cable into my JetKVM, JetKVM only turns on when the connector is oriented one way. When I reverse the orientation of the connector, JetKVM does not seem to get powered on (i.e. the screen never lights up). Since USB-C connectors are supposed to work just fine no matter their orientation, I must admit to being a little puzzled by this behavior.

It would be interesting to see how all of the USB-C signals are connected to silicon within JetKVM.

[osirisinferi]

They probably only connected a single 5.1 kΩ pull-down resistor to either CC1 or CC2, but not both. My JetKVM I just received today also only powers on when the USB-C to USB-C from a "smart" charger is oriented in one way, but not the other.

There's only a single CC (configuration channel) in the USB cable (CC1), so the CC1/2 on the charger side will only connect to a single CC1/2 on the JetKVM side. If one of the two CC pins on the JetKVM side has the pull-down resistor, but not the other, the orientation of the USB-C cable will matter to enable a "smart" charger.

This is only relevant for USB-C "smart" chargers which do not output 5 V all the time, but only "on demand" depending on what's connected to them. "Dumb" USB-A chargers don't have this "limitation". My JetKVM powers on fine when using the Y-split cable in combination with a "dumb" USB-A charger. Tried all 4 orientation combination of both sides of the Y-cable, all worked.

By the way, no reason to use expensive "smart" chargers, any cheap (wouldn't recommend chargers from Ebay or AliExpress et c. though, those are a fire and/or electrocution hazard) "dumb" USB-A charger will do. While idle, my JetKVM only used about 100 mA.

Edit:
Opened up my JetKVM and measured the resistors inside:

• on CC1 there's a 5.1 kΩ pull-down resistor to ground, as expected;
• on CC2 there's just a 64 Ω resistor to ground?

According to one of the major LLMs out there this 64 ohm resistor on CC2 is "wildly out of spec and looks nothing like any valid termination defined in the USB-C spec".

Not sure why that CC2 resistor is so low, maybe JetKVM can reply?

[rmschooley]

Yes, I completely agree with your analysis. I am just wondering if this was intentional or not as it seems like a rather big oversight. I definitely hope they are able to comment on this.

[systemmonkey42]

I found a comment somewhere which suggested the USB-C splitter wasnt properly enabling USB-PD.

If you plug the USB-C splitter in, a USB-A to USB-C can be used to power it, and a USB-C to USB-C can be used for usb control.

Using USB-C to power it (via a power brick or a USB-C to USB-C cable) plugged into the splitter doesnt work at all for me.

Using USB-C to USB-C direct (without the splitter) seems to work fine.

Lots of discussion about this here #393

[osirisinferi]

There might be multiple issues:

• seemingly incorrect CC2 pulldown resistor, making the entire JetKVM react differently to the orientation of the USB-C -> USB-C cables when using PD/PPS chargers;
• Y-cable issues.

I've only noticed the cable orientation issue due to the 64 ohm CC2 pulldown resistor and have not noticed any issue with my (all black) Y-cable (ordered just recently).

Edit: after some testing (see below) it seems when posting the above I only used an USB-A to USB-C cable with the Y-cable..

[systemmonkey42]

I've only noticed the cable orientation issue due to the 64 ohm CC2 pulldown resistor and have not noticed any issue with my (all black) Y-cable (ordered just recently).

I did some un-scientific testing on this...

USB-C power brick, cable from brick to device..

• orientation of cable at brick end makes no difference.
• orientation of cable at JetKVM end matters.

USB-C power brick, cable from brick to splitter power connector (end with lightening bolt in case not everyone has picked up the difference) splitter to device

• No combination of cable orientations at any point will power up the device.

With a USB-A brick, and USB-A to USB-C cable, it always just works, with and without the splitter.

[horst789github]

When using the Y-Split cable, I get nothing.

same problem here... i got my JetKVM today and the YSplit dont work.

[osirisinferi]

USB-C power brick, cable from brick to device..

* orientation of cable at brick end makes no difference.

* orientation of cable at JetKVM end matters.

Yes, that's expected with the incorrect CC2 pulldown resistor, as the power adapter would be able to check both CC pins at its end (so there orientation doesn't matter), but only one of those pins would be connected to one of the CC pins of the JetKVM due to how USB-C cables work (just a single CC is connected). If that single CC core is, by 50/50 chance, connected to the CC2 pin of the JetKVM, it won't work.

USB-C power brick, cable from brick to splitter power connector (end with lightening bolt in case not everyone has picked up the difference) splitter to device

* No combination of cable orientations at any point will power up the device.

Can confirm this, Y-cable doesn't like USB-C to USB-C cables cq. PD/PPS adapters. Can't check which pins are connected in the Y-cable though, don't have any spare USB-C receptacles laying around, yet.

[scottgrobinson]

Thank you all for your input - USB-A to USB-C did the job here. Not ideal but hey... At least I've got something I can use now :)

[RuggedPineapple]

Was having issues with this, in the end I went with a 10 dollar usb3 hub that takes 5v over usbc to provide spec power to the out ports. Solved the issue of providing power with the host off while also only using a single cable to the jetkvm because I assumed the y cable just didnt work after it failed when i first set up my unit. Kinda wished I had seen this issue, but in the end its not a terrible solution. If anyone else wants to go that way, I dont want to link for spam filter reasons but the amazon title of the hub i used is "Acer USB Hub, Multiple 4 Ports USBA Splitter for Laptop with Type-C Power, Extender for A-Port Laptop, PC, Desktop and More (2FT, USB-A 3.0)"

[osirisinferi]

Thank you all for your input - USB-A to USB-C did the job here. Not ideal but hey...

Guess that's why they provide a USB-A to USB-C cable with the device 😉

[adamshiervani]

Closing this one out — the Y-split power issue is a hardware/cable limitation, not something addressable in firmware. If you're hitting this, reach out to support for cable compatibility guidance.