I connected my iPad Air M1 to my MBP M2 Max using a TB cable. I am able to show the screen of the iPad on the Mac using Quicktime recording and selecting the iPad as the screen in Quicktime. What I would like to know is how the screen data is getting from the iPad to the Mac. I turned off WiFi on the Mac to eliminate the possibility that there was a wireless connection. So, I am pretty sure the data connection is over the USB connection. System Info shows the iPad connected as USB. I could not find anywhere in System Info where DP alt mode status is displayed. Is there anyway to confirm or rule out DP alt mode?
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DP alt mode
- Thread starter steve123
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I looked at the displays on the Mac in System Info but only the built in display appears there when Quicktime is displaying the screen. I will dig into the IO Registry a bit ... that sounds like a good place to look. Thank you.
I found some interesting info in the IO Registry. The first screen shot shows the display crossbar which references both ufp and dfp. So, that suggests that there are both source and sink capabilities.
The second screenshot shows the info for the dfp's. Seems backward to me but we can clearly see there are three ports with DP Alt mode corresponding to the three USB C ports on the MBP. There is a fourth DisplayPort interface connected to the HDMI port. Unfortunately, when open the screen using Quicktime and close Quicktime, there does not appear to be any difference.
The second screenshot shows the info for the dfp's. Seems backward to me but we can clearly see there are three ports with DP Alt mode corresponding to the three USB C ports on the MBP. There is a fourth DisplayPort interface connected to the HDMI port. Unfortunately, when open the screen using Quicktime and close Quicktime, there does not appear to be any difference.
It's not a DP alt mode, it's just a H.264 or HEVC video stream sent over the USB.
Thank you for the feedback. Yeah, this is what I suspected was going on ... there is a pretty big lag in the display response on the Mac of about 0.5 sec or more.
Thanks you for the clarification of "atc" ... that makes things much more understandable.
Does anyone know if the Mac ATC can be configured as a DP sink? That is, can it receive a DP stream? The reason I ask is I had this crazy idea of interfacing an RP2350 to the Mac using DP alt mode to stream data from the PIO.
