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This publish/query is referencing the iphone macbook connections challenge reported by @Avelj (thanks in your particulars evaluation, that helped lots) intimately on this thread:
iPhone-Mac connection challenge and what does the usbd course of do?
However since it’s a must to have “status” factors to submit a solution not least a remark I’m compelled to open this new thread as an alternative!!! (Nicely, not such a very good system ultimately)
I would ramble a bit, tl;dr on the backside…
The problem:
As offered within the referenced publish connecting an iPhone to my MacBook Professional Mid 2015 (MacBookPro11,5) would end result repeatably in disconnecting and reconnecting the iPhone. This is able to make the connection unimaginable to make use of for Ethernet or Sync and impacts additionally the efficiency of the MacBook: Each time the iPhone would disconnect the MacBook would freeze for half a second, being very seen when watching a film/present on Netflix. This bugged me for years as I couldn’t perceive what the problem may be.
It was reported that this might be solved with both a brand new lightning cable or disabling the usbd course of on the MacBook, however in case of the cable would in all probability resurface solely month later. Each options are dissatisfying, as I for one would not wish to buy a lightning cable each month or so. And second disabling the usbd course of by way of sudo killall -STOP -c usbd would remedy the freezing however scale back the charging energy to abysmal 300 mA.
The investigation:
I examined varied iPhones (XS, XS, 8, 5, 4) and all confirmed the identical challenge. I used totally different lightning cables, no change. I used a distinct Macbook Professional (2008) and a a Mac Mini – identical with the outdated MacBook, however the Mac Mini works like a appeal.
So I took a more in-depth take a look at the software program stage however quickly realized that the problem couldn’t be resolved this fashion, because it in all probability hat to do with charging energy and connection points from the iPhone itself, because the connection would solely fails because the charging energy will increase.
Therefor I checked all parameters relating to this and located iStatMenu to be an excellent software to test the charging energy. The 5V USB rail confirmed a consumption of 0 mA for a suspended state and ~20 mA for energetic state with no USB equipment related. This consumption ist most definitely the usual present draw from the Trackpad and Keyboard related to the USB controller internally on the MacBook Professional 2015.
Then I related the iPhone to both USB ports and will monitor the present consumption: With a disabled usbd course of it will rise to 500 mA constantly and be very steady. However charging the iPhone this fashion would take ages and in some instances, when the iPhone was used apart the MacBook lead to no cost in any respect.
When resuming the usbd course of with sudo killall -CONT -c usbd the present draw would enhance to 600 mA or extra however be very unstable and drop again all the way down to 400 mA leading to a buzz from the iPhone reporting a dis- and reconnect.
You may really see this within the following image: A depicts the energetic state with out USB connections. B the related iPhone with usbd disabled. C with usbd enabled. The present draw reaches 600 mA and brakes down earlier than reconnecting repeatedly.
The ultimate answer and my opinion, on what causes this challenge please learn my very own reply under… 🙂
TL;DR: The problem of reconnecting iPhones on Macbook/Professional seams to be repeatably brought on by the USB sockets within the MacBook and/or the USB connectors on the used lightning cable. Contact resistance of the connector prongs makes the iPhone disconnect and reconnect in excessive energy charging mode.
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