MacOS – USB devices intermittently disconnecting

keyboardmacbook promacosmouseusb

For a long while now I've experienced USB devices intermittently disconnecting on my Macbook Pro Retina 2012 (El Capitan 10.11.2).

I'm currently using a Targus 7 port USB 3 hub (http://targus.com/au/usb-30-7-port-hub-with-fast-charging) but this problem existed when I was using an older USB hub. I bought this one in the hope it might resolve this problem, but it didn't.

This USB hub is connected to its power adaptor.

From memory this problem also existed before El Capitan update.

For work I use Microsoft Lync for Mac, and I sometimes notice than when a new instant message arrives, my keyboard, mouse and headset will disconnect. But they also sometimes disconnect without this trigger.

To reconnect them, bizarrely, i seem to need to unplug and replug each device in 3 times specifically.

It's very frustrating and inefficient for my workflow. Just wondering if there are any suggestions or recommendations as to how I can troubleshoot or resolve this?

Following are screenshots of the USB map (two separate screenshots as the contents of the USB 3.0 Bus details page didn't fit in one screen)

Page 1

Page 2

Best Answer

Disclaimer: this is an answer under construction.

Open the  > About This Mac > System Report..., select Hardware > USB, and open every small ▼.

Select the USB bus where is connected your USB hub, and enlarge the lower part of the window to have a complete vue of all your USB equipments.

Make a screen capture: commandshift4, space, select the USB map window and click. You will get something like:USB config

Include this screen capture within your OQ (original question).

Verify that the sum of the Current Required (mA) of all the equipments connected to the same internal USB hub don't exceed the Current Available (mA) for the hub. This value might be different depending on the USB port available outside and what is already connected on it internally.

As a basic simple rule, avoid the external USB port which is on the bus where is connected the FaceTime HD camera (Current Required (mA) = 500 mA). For example, on a MacBook Pro, I discovered through trials that my FaceTime HD camera is on the bus with the USB external port nearest from the front.

To check this hidden cabling, just use your external mouse.

Connect it on port nearest from the front. Hit commandR in System Report... to refresh the USB connection information. Note on which bus is this external USB port.

Repeat the same operation for port farthest from the front.

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