ATX Extension: LED display dosen't work if case doesn't have LEDs

[berglh]

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Note

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Disclaimer

• I have read and understood the disclaimer.
• I plan to implement the feature myself.

Subsystem

Hardware

Feature description

I have both the JetKVM and the ATX extension board. After figuring out the polarity issues with the switches due to the FET on the ATX extension board, I've noticed that the LED indicators in JetKVM are not showing in my UI. I've confirmed the polarity is correct as per the MB and ATX extension board.

The issue I believe is that my case actually does not have any HDD or Power LEDs, so I am unable to plug an LED into the ATX extension board header on the case side, which in turn means the circuit is not completed with an LED.

1. Ideally, it would be great if there were a way to toggle a no-case LED option to allow the LED notifications to operate anyway in the UI, or if it safe to do so, perhaps provide jumpers in the kit for the pins to complete the circuit for cases without LEDs. My server is in a minimal MiniITX case (NCASE T1) without any LEDs.

   Edit: A quick googling around seems like jumpering LED pins are shorting the link without proper load/resistor and could damage the GPIO pins of the ATX extension board - I'm guessing this is not supported xD

2. It would be appreciated if the documentation for the ATX extension board could be improved to make both the switch polarity and requirement for the LED to be plugged in for the indicator to work in the UI.

[dseven]

There shouldn't be a need for case LEDs. The motherboard should be presenting 5V between the pins when the LEDs should be on, and the extension should be able to sense that. There is no single circuit that needs to be completed for that. Perhaps the pins on your motherboard are not actually active? I don't think it should make a difference, but I suppose you could try emulating an LED's load with a resistor around 250-500 ohms. You could try measuring the voltage too, if you have a multimeter...

[berglh]

Bought a multi-meter. I measured the PWR LED +/- pins on the ATX extension board that would otherwise go to the case LED and I'm only seeing 10s of mV on it at most. Is it possible that it matters what pins from the ATX extension are plugged into the board? I currently have the main block ribbon cable supplied with the ATX extension card that plugs into the motherboard plugged in to the lower half of the pins closest to the ATX extension card PCB, should this be on the half of pins further away from the PCB?

[dseven]

No, each pair of pins is directly connected together on the PCB, so it doesn't matter which row you use.

I suppose you could try putting a load resistor - maybe 330ohms or thereabouts - across the pins that could normally connect to the case LED and see if that makes a difference...

[berglh]

I bought several 360 ohms resistors and had a spare dupont female to female two wire cable. I plugged the resistor into one end of the female pair. I was able to measure 360 ohms via the dupont plugs at the other end of the cable. I plugged that into the power LED +/- header on the ATX extension board and found no real change. In terms of voltage I was only seeing 180 mv across the resistor wires, similar to what I was measuring on the ATX extension board. Which is more or less what I saw before without the resistor.

I confirmed the correct polarity on the MB, but tried swapping the wires from the ATX extension board to the MB just in case the documentation on the MB was wrong. Unfortunately, I don't seem to have a case LED to try out to ensure the MB is actually working so I can't actually rule out the MB at the moment. Might need to order a generic front panel kit off AliExpress or something so I have an LED I can try out.

I tried powering off the system, rebooting the JetKVM, loading/unloading the ATX extension module etc - nothing seems to get the power activity in the UI to appear.

The MB is Asus B850-I Gaming which I bought because it supports 4x PCIe x4 lane bifurcation of the x16 slot that I use for a 4 slot NVMe expansion card. The manual looks pretty standard for front panel system header:

[berglh]

I figured it out. Essentially the stealth mode (which disables the motherboard RGB LEDs) of the Asus B850-I Gaming motherboard disables all LEDs, including power and HDD LEDs. I can confirm everything is working as expected when I disabled stealth mode.