Question on Docking Station - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: June 29, 2024, 09:34:51 am
content: I have this docking station -https://www.dell.com/en-in/work/shop/dell-dock-wd19s-180w/apd/210-azcs/docksMy question is. what's the principle, concept behind the fact that, the user just needs to connect the Type C port on the laptop and he can connect two monitors using HDMI, DP port and extend his laptop screen to two monitors (one using HDMI and the other using DP port on the dock). Once done, I can play Youtube on One monitor, Netflix on the other and a different streaming channel on my laptop.This is really amazing. What's the concept behind this? I understand that, it's just like playing these streaming platforms in different Google Chrome tabs using a single laptop screen. But at the same time, I am able to view the different screens. So, data transfer is definitely happening almost instantly. How come all the data from DP, HDMI ports (monitors connected) are interfaced?How can just a simple type C port connection, enable simulataneous data transfer from different monitors with different ports?

author: Psi
author_rank: Super Contributor
timestamp: June 29, 2024, 09:46:26 am
content: Usually there is only 1 or 2 USB-C ports on the laptop that support the docking station.They are special USB C sockets that also support a thunderbolt connection at 40 Gbit/s.USB and thunderbolt are HUB type protocols you can daisy-chain multiple devices on them and they all just share the bandwidth of the single connection.One 60fps 1080P uncompressed display stream only needs around 3.6 Gbit/sSo there is plenty of bandwidth for a few displays, extra usb ports, lan, audio and everything else all at once.Even a typical USB C port can do 5 Gbit/s, enough for one 1080P 60fps stream.Sometimes you will see cheap USB C to dual display adaptors, like HDMI+VGA.A lot of the time they only do 30FPS to stay within the 5 Gbit/s limit

author: xvr
author_rank: Frequent Contributor
timestamp: June 29, 2024, 09:56:19 am
content: The TypeC USB3 connector can tunnel other protocols using USB3 physical media. One of them is Thunderbolt. It's a supersede of HDMI and a bunch of other multimedia related. For churging USB3 use PowerDelivery protocol.So docking station just use all features, available in USB3 specification.

author: nomead
author_rank: Contributor
timestamp: June 29, 2024, 05:02:35 pm
content: These older USB3.1/3.2 docks use DisplayPort alternate mode for display output and USB-hub for other stuff including the audio and ethernet. To use such a dock you need to have so called USB-C full feature port (data, USB PD and DP) or Thunderbolt port. HDMI is usually taken from DisplayPort data stream through a converter chip because DisplayPort converts to HDMI with little effort but not really the other way around. Thunderbolt ports can output display data in Thunderbolt protocol but not too many displays have Thunderbolt inputs so they revert to Displayport alternate mode too.

author: Freshman
author_rank: Regular Contributor
timestamp: June 30, 2024, 08:07:04 am
content: Thank you for your answer.Can you please explain on what you meant by "HUB type protocols"and a few more follow up questions:1. For sharing the bandwidth of the connection, should all the devices need to be connected/configured (not sure of the exact term) in daisy-chain format.2. Can you explain the calculation of 60fps 1080p into 3.6Gpbs?

author: Psi
author_rank: Super Contributor
timestamp: June 30, 2024, 08:33:00 am
content: Quote from: Freshman on June 30, 2024, 08:07:04 amI just mean that its a protocol that allows for many devices to connect. Including devices that create more ports for more devices. The computer talks directly to all devices on the bus. The computer doesn't need to mix multiple different signals together, that is done in hardware. The computer isn't really talking to its USB-C port, it's talking to all the devices on the bus.Quote from: Freshman on June 30, 2024, 08:07:04 amThe data rate is limited by the USB protocol. Engineers design their USB devices to use less than the total available datarate. The engineers also consider what to do if the USB bus is busy and they can't get the data rate they want. The design the USB device to handle this situation. A USB to HDMI adaptor for example would probably lower the frame rate or just skip frames. Other devices may refuse to work or show errors if they can't get the data rate they need and can't function because of it. Like in real time monitoring.Windows will also warn you if you have too many USB devices on one USB bus.Quote from: Freshman on June 30, 2024, 08:07:04 amI googled it and went with the first result, it looks like the actual value is 3.73Gbps.1920×1080=2,073,600 pixels per frame2,073,600 pixels × 30 bits color info per pixel = 62,208,000 bits per frame62,208,000 bits per frame × 60 frames per second= 3,732,480,000 bits per second