Mac and daisy chained monitors

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Mac and daisy chained monitors

My goal was to have a single cable to my laptop that recharges the laptop, drives two decent monitors, a decent set of speakers, an external webcam(s), a Logitech keyboard and mouse, and a wired network connection. Essentially have the monitor(s) act as a dock.

I have been successful so this post answers my earlier question, but I've found some issues so I'm hoping the community may have an answer.

Here are my issues, hardware detail and background is below.

First off, when I use the MBP 16" everything works perfectly.
When I connect a HP Win10 laptop everything works perfectly except the laptop does not charge. It does not appear to recognise that the LG monitor is a PD device that can provide power. The same port on the laptop will charge from any other USB-C charger I've tried including Apple 61W & 96W USB-C charger, HP charger, and unknown brand USB-C dock.
When I connect a MBP 13" running macOS 11.2.1 everything works except (a) video on the LG (blank screen), note the speakers on the LG work as do the peripherals connected to the LG. And (b) the Philips monitor works but the picture has vertical lines (see photo attached).
When I connect a MBP 13" running macOS 11.5.1 the video on netiher screen works, but all the other preipherals do work properly i.e. speakers. webcams, microphones, ethernet, Unify receiver etc...

With 3. and 4. if I unplug the cable that connects the LG monitor to the Philips then the MBP 13" connects and everything works perfectly.

The equipment

MacBook Pro 16" 2019, macOS Big Sur 11.4
MacBook Pro 13" M1 2020, macOS Big Sur 11.2.1 (upgraded to 11.5.1 now)
HP EliteBook x360 1030 G3 (2ZV64AV), Windows 10 Enterprise 10.0.19042. This does support ThunderBolt 3
LG Ultrafine 4K 24" (24MD4KL) monitor, firmware 3.03,5249,4.13,0.3,39,6.59
Philips 243B9/75 monitor, connected to the Thunderbolt daisychain port on the LG
Logitech StreamCam
Rapoo C260 webcam
Logitech MK545 keyboard, mouse and Unify receiver
Satechi USB hub and ethernet adapter

This is how its connected

This is what the Philips screen looks like in 3b.

Cross posting this to LG and Philips support

MC

MacBook Pro 16″, macOS 11.4

Posted on Aug 8, 2021 5:38 AM

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Answer 1

Top-ranking reply

leroydouglas

Community+ 2024

Level 10

188,466 points

Aug 8, 2021 6:40 AM in response to somekiwi

somekiwi wrote:

My goal was to have a single cable to my laptop that recharges the laptop, drives two decent monitors, a decent set of speakers, an external webcam(s), a Logitech keyboard and mouse, and a wired network connection. Essentially have the monitor(s) act as a dock.

I have been successful so this post answers my earlier question1. , but I've found some issues so I'm hoping the community may have an answer.

ref post: " My question is about daisy chaining a USB-C monitor from the LG monitor. and driving the LG monitor with the MBP."

The Mac has never supported daisy-chaining large displays.

You can put each display on its own ThunderBolt port if you want them to work.

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Answer 2

somekiwi Author

Level 1

9 points

Aug 9, 2021 11:04 PM in response to leroydouglas

That is incorrect, I have it working perfectly in my own office using my MacBook Pro 16. I can, and have, daisy chain a 4K + 1080p monitor or two 4K monitors using Thunderbolt 3.

If you don't believe me its also on the product websites I linked to in my original post

4K Daisy Chain - Establish a dual-monitor environment by connecting two 4K monitors and a laptop using a Thunderbolt™ 3 cable.

With two Thunderbolt 3 ports for daisy-chaining, you can easily set up dual UltraFine 4K Displays by simply connecting a single Thunderbolt 3 cable to your MacBook Pro or MacBook Air.

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Answer 3

somekiwi Author

Level 1

9 points

Aug 10, 2021 6:40 PM in response to somekiwi

RE issue 2. in my list. Add a little bit more info in case it helps. I used a USB-C inline power meter, and got the following.

(a) This is the MBP 16" plugged into the LG monitor and drawing charge normally. You can see the direction of charge, volts & amps drawn etc

(b) And this is the HP x360 plugged into the same LG monitor (and cable etc) but not drawing a charge

[Sorry imgur link as the photo won't upload here https://imgur.com/a/3kYEYLr]

I did a firmware update on the HP x360 laptop and I am now getting the following error message when I plug the LG monitor in "HP recommends using an HP power source" and then "Smart AC adapter power output is too low for this computer". Note that the HP laptop draws a max of 65W and the LG provides up to 85 (both use USB PD).

After reading this article I think its possible that HP are blocking the LG monitor from charging the laptop, effectively HP are maintain a whitelist of allow USB PD chargers that the HP laptop enforces.

https://gtrusted.com/review/54789

However I've made no progress on why the MBP 13" M1 doesn't drive both monitors when the MBP 16" does.

MC

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Answer 4

somekiwi Author

Level 1

9 points

Aug 10, 2021 6:08 PM in response to somekiwi

Just in case what you mean by "large displays" is over 4K resolution, I should add that I do understand (and agree) that a single Thunderbolt 3 port can not handle the bandwidth necessary to daisy chain 2 x 5k monitors, but that is why I described the exact gear I am using in this scenario in my original post i.e. a LG 4K 24MD4KL monitor (24" 4K) and a Philips 243B9/75 monitor (24" 1080p).

MC

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Mac and daisy chained monitors

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