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USB-C devices not powered after reboot

S

samitro

macrumors newbie
Original poster
Mar 18, 2022
17
1
I love the setup with one usb-c cable between my macbook and external monitor utilizing the hub built in the monitor. I have Macbook pro 14" with M1 pro and LG 27UP850-W. All works fine, the only problem is that after reboot, the usb hub in the monitor stops working and I need to either restart the montor (turn off/on) or replug the usb-c cable to the macbook. I have read many users are facing the same behaviour with other monitors as well. I believe some monitors' hubs are powered by the connected device (macbook in my case) as connected devices will not power on without plugging the cable to the macbook.

So I was trying to figure out why the monitor hub was not powered on after rerboot. I connected an ipad pro to the macbook using a usb-c to usb-c cable and indeed it also stop charging after reboot and is not visible in the system report under usb. After further troubleshooting, I figured out that using USB-C to USB-A cable with USB-A to USB-C adapter works well and the ipad keeps charging after reboot. I tried this with the monitor and indeed it works, the hub is working after reboot but display is black as the USB-C to USB-A cable doesn't transfer video which is expected.

Any idea why a device connected to the macbook with USB-C to USB-C cable is not powered on after Macbook reboot? is tthis an extected behaviour? Tried Apple support chat but they were useless. Could that be one of the bugs introduced with Monterey described here? https://www.macrumors.com/2021/10/29/monterey-usb-hub-issues-reported/

Many thanks
 
the last monitor I can think of that had everything figured out with respect to external devices was the Apple LED Cinema/Thunderbolt Display. Every dell/lg monitor I've used has wildly inconsistent behavior with the built in hub, low power limits and poor performance, to the point where I don't bother using the built-in hubs anymore and just opt for external powered hubs except for maybe the odd keyboard and mouse temporarily.

Not saying there isn't an issue with Monterey, just that I'm not a fan of most monitor hubs.
 
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Just in case anyone comes across this thread. In relation to an ipad/Android device plugged to USB-C and stopping to charge after macbook reboot, it seems that this could be related to which device charges the other.

Charge and connect with the USB-C port on your iPad - Apple Support

Use the versatile USB-C port on your iPad to charge, connect to accessories like external storage devices, cameras, and displays, and power other devices.
support.apple.com support.apple.com
  • If you have two iPad models with USB-C ports, you can connect them directly with a USB-C cable. One iPad will draw power from the other. If you want to change which iPad charges, unplug the USB-C cable and then reconnect them.
An android device plugged into Macbook's USB-C port uinsg USB-C to USB-C cable will stop charging after macbook reboot. But when I go into USB settings, I see under power options an option that says "charge connected devices" and it s enabled after macbook reboot. If I disable it, the android device starts to charge. So I'm guessing that the macbook during boot is negotiating something wrongly with the USB-C connected device. I believe there is no such option on the ipad so the only option is to replug the USB-C cable. Whether this has anything to do with the monitor hub, I have no idea.
 
What cables are you using to connect devices. Are they OEM apple cables? It could be the cable itself.

I have been bitten by those USB-C to USB-A cables but that was back when USB-C was brand new and the cable OEMs didn't really know what they are doing. The one I have will cook the USB controller if you try to draw too much power through USB-C. Hey maybe thats a feature! I'm sure there are better ones out there now.
 
samitro said:
Just in case anyone comes across this thread. In relation to an ipad/Android device plugged to USB-C and stopping to charge after macbook reboot, it seems that this could be related to which device charges the other.

Charge and connect with the USB-C port on your iPad - Apple Support

Use the versatile USB-C port on your iPad to charge, connect to accessories like external storage devices, cameras, and displays, and power other devices.
support.apple.com support.apple.com
  • If you have two iPad models with USB-C ports, you can connect them directly with a USB-C cable. One iPad will draw power from the other. If you want to change which iPad charges, unplug the USB-C cable and then reconnect them.
An android device plugged into Macbook's USB-C port uinsg USB-C to USB-C cable will stop charging after macbook reboot. But when I go into USB settings, I see under power options an option that says "charge connected devices" and it s enabled after macbook reboot. If I disable it, the android device starts to charge. So I'm guessing that the macbook during boot is negotiating something wrongly with the USB-C connected device. I believe there is no such option on the ipad so the only option is to replug the USB-C cable. Whether this has anything to do with the monitor hub, I have no idea.
Click to expand...
Hi, I have the same problem with LG 27UP850-W. I tried different usb c/ thunderbolt 3 cables, but it doesn't solve the problem. My 1in to 6out usb-c adapter doesn't have this issue. Have you find any solution instead of replug the cable.
 
bigplume said:
Hi, I have the same problem with LG 27UP850-W. I tried different usb c/ thunderbolt 3 cables, but it doesn't solve the problem. My 1in to 6out usb-c adapter doesn't have this issue. Have you find any solution instead of replug the cable.
Click to expand...
No, unfortunately not. This requires either a firmware update from LG or fix from Apple, I suspect it is related to MacOS. 12.3.1 was just released but didn't install it yet to test.

I bought a USB-C hub for 30$.
 
samitro said:
No, unfortunately not. This requires either a firmware update from LG or fix from Apple, I suspect it is related to MacOS. 12.3.1 was just released but didn't install it yet to test.

I bought a USB-C hub for 30$.
Click to expand...
It's a pity, I will contact LG customer service, hope they can do something...
 
I doubt they will as its works well in windows but give it a shot.
 
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