iPhone connects and disconnects from Mac

Thanks for the tip.

However in the above scenario my Macbook was jumping from any desktop i tried to work in back to the desktop where I was running iTunes. By the time I had selected any other app (terminal included) I was thrown back to iTunes because it wanted to show me a message. I never saw this message because it got hidden behind the iTunes window. I only discovered the message after taking a guess at what was going on. So with terminal I would have had no chance to type anything, because as soon as I selected the correct desktop (where I keep terminals assigned) I would not get the time to even select the terminal let alone be able to type something into it. It would be far better if this message (regards trust) was thrown up in the notifications sidebar where it would have less influence on the behaviour of Apple's display manager. But seeing Apple have done nothing to improve the display manager with regard to the reliable positioning of apps on desktops I don't expect a change in this area either - a means to interrupt the display manager when it goes berserk - not even being able to reboot via the applet on the top left of the screen. My only solution was to log in from another computer and reboot.

At this point (remote terminal via SSH) using "sudo killall -STOP -c usbd" would have saved me rebooting.

This issue appears to often be related to the power on the phone. When it's on a very low charge, it doesn't connect properly. (However, it seems to continually cycle through trying to connect, flashing on and off. Which is not really very helpful to the device or toubleshooting.)

I'm not sure what the minimum charge it accepts is, but as long as your device is charged to 'out of the red', you should be okay.

This is most annoying. I'm having these issues with a USB connection between iPad or iPhone connecting to iMac. Only solution is to force quit USBD from Activity monitor (or terminal method). This solves it while iPad or iPhone is connected. Once devices are disconnected, this will happen all over again when next plugged in.

When force quitting USBD and as an indicator that things are not right when plugging in device afresh, device constantly asks me to enter PIN number to trust device...

It's not - energy based (ie battery less than 60%)

It's not - a cable issue

It's not - Reset Location & Privacy settings on iPhone or iPad

It's not USB port on iMac - others have same results

Because it doesn't happen with same devices and cables at all when I connect iPhone or iPad to MacBook Pro.

Restarting iMac doesn't help either.

Any ideas what can be done here?

Thanks

I've had this problem for ages and finally found a solution.

On my iMac I went to - System Preferences - Network - iPhone

step1. untick disable unless needed

step 2. press on Set Up Bluetooth Tethering and turn bluetooth OFF.

Finally press apply.

Hope this works for you!

I also had this problem for a long time but trying solutions posted so far such as stopping usbd only worked sometimes. I now have the suspicious the root cause might be that this rapid connect/disconnect only happens when the iPhone is <100% charged so that the iPhone is using the USB connection with PC/laptop to charge itself while trying to use is as real communication link at the same time. Bringing the iPhone 100% charged seems to work OK although the link still flips a few times before settling down. Best would be if anyone knows how to stop the USB connection being used for charging temporarily from PC/laptop or iPhone side.

Alas this did not help me. There is no "iphone USB" option on my Mac.

Tried all methods that you guys left here, still nothing.
Maybe someone know how to solve this issue ?
I have great connect via wifi (Waltr 2, iMazing), but reconnect loop via usb 😟

same here. i have 4 cables and all of them, the same thing happens. keeps connecting and disconnecting. this is not a problem of our phones or computers. im sure its something they did in the os.

This is so frustrating. Tried all of the above. Cahrged an uncharged. It worked a couple of times ... and couple of times it was madness... so annoying.

Look at this article If you see "Software update is required to connect to your iOS device" on your iPhone, iPad, or iPod touch - Apple Suppo…

thisisyouranswer was the answer I needed. It was hard to get to with the phone grabbing iphoto over and over but I got it eventually

It's definitely Apple's fault in OSX. If I start on the windows partition, the problem doesn't occur...

Actually,

sudo killall -STOP -c usbd

is also only a temporary fix

🤬

This worked for me. I charged it to 85% and problem is gone!

I tried all the helpful hints left here:

1) Used an original Apple cable

2) Tried to sync only when my iphone battery was > 80%

3) Reset privacy and location settings

4) Changed network settings on the laptop as suggested (USB and Thunderbolt)

5) Rest my phone completely

6) Reset PRAM and SMC on the computer

Guess what? the problem still persists. I never thought I'd say this but I'm fed up of my iphone now. It seems that the people at Apple are not even listening to its customers anymore. This problem has persisted since 2013 but no solution till date.