Do USB-C monitors use the USB as a video input? - Page 1
Forum section: electronics / general

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 11, 2021, 02:15:01 am
content: I've tried reading the various descriptions but it's not clear to me what the USB-C on these monitors does. It makes sense for a laptop to recognize it as a display device, but would the monitor know what to do with a microscope?I have one of these generic Chinese USB 3.0 microscopes, model H3, not much info available on it, but it has a USB 3 connection.Can I plug the microscope to a monitor that seems to use UCB-C as an input and see an image?

author: ataradov
author_rank: Super Contributor
timestamp: October 11, 2021, 02:21:03 am
content: USB-C connector carries multiple different protocols. In case of the monitor, if it claims to be able to display anything over USB-C, it would be using Thunderbolt for the actual signalling. There is nothing from the classical USB is left in this case for the picture transfer.Typical camera/microscope presents itself as a audio/video device. There is no way that monitor would display anything or even recognize that device. Cameras need to be connected to a real USB host.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 11, 2021, 02:28:18 am
content: Thanks, yeah, something didn't make sense for sure. I guess I'll shop for a microscope with a built-in display or a HDMI output.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 11, 2021, 03:25:11 am
content: Quote from: evb149 on October 11, 2021, 03:06:41 amYup. Usually I try to figure out things myself but in this case I am baffled.

author: Berni
author_rank: Super Contributor
timestamp: October 11, 2021, 06:31:15 am
content: Yep this is the reason i find USB-C a complete standardization trainwreck.It is now possible to run almost anything imaginable via USB-C, but there is no way to know if it will actually work until you plug it in and try it since both devices must support that one specific feature out of many in order for it to work. Bringing back the ol phrase "Plug and Pray" despite USB 1.1 being the port that truly pulled us into the "Plug any Play" paradime where things simply worked once plugged in.The only thing guaranteed by a USB-C port is having USB 2.0 support. All the other features like USB 3.0, USB 3.1 Gen2, HDMI, DisplayPort, Thunderbolt...etc are entirely optional so a host PC may support any combination of these it likes, and its impossible to know which since there is no requirement to place standardised icons for the supported features next to the port.To make things even more confusing even host machines have the same USB-C port as USB devices. So the new symmetrical cables allow you to connect two host PCs (Where nothing will happen because they expect to see a USB device) or to connect two USB slave devices (Where nothing will again happen because they are both waiting for a host to talk to them)Your case of a USB-C camera and USB-C monitor combines all these cases of how USB-C can go wrong. As a consumer you would expect this to work because they have the same port and you have a cable that fits both. However the camera is likely a USB 3.0 slave device while the monitor is likely a HDMI/DisplayPort slave device. So its two slaves that will not talk to each other, and even if they did, they do not use the same protocol to talk and thus could not understand each other.

author: Ranayna
author_rank: Super Contributor
timestamp: October 11, 2021, 11:01:15 am
content: @Berni: You are hitting all the points why i do not like USB-C. Mechanically that connector might be really good. Well, at least it's better that Micro- or *shudder* Mini-USB. :pBut USB did away with a big principle that mostly held true (PS/2 is the one exception i can think of) in the home PC market: If the connector fits, you can expect it to work. Maybe not at peak performance with Fast Ethernet and Gigabit Ethernet, or USB 2 and 3, but it should still work. Even the analog audio jacks have become smart enough to figure out if what is plugged in is a input or output device. Or at least can be remapped in software.USB-C with all the stuff it supports did away with that and you need to know exactly what the host, the device, and the cable can support. Any of these components can be the reason for issues.And to know what each device supports you soon will need to be an expert in pictography :p"Plug-and-Pray" really is the best expression for the mess that is USB-C.I wonder how long it will take for the first cheap fake "240 Watt capable" USB-C cable to burst into flame.

author: tszaboo
author_rank: Super Contributor
timestamp: October 11, 2021, 11:31:42 am
content: Quote from: Berni on October 11, 2021, 06:31:15 amIt becomes even worse if you add on power delivery. My laptop has Type-C charging, but it just becomes unreliable if that is used. "You know it's like magic, data goes this way on the cable, power goes the other way on the cable", and the connection fails for a few seconds every few hours. I miss the old docking station, which had a hundred pins, and it worked every time. Unless if you disconnected without pressing the button, maybe BSOD if you did that.With USB-C, what powers what is not that simple. Is the portable monitor supposed to power the camera, or the other way around?

author: Berni
author_rank: Super Contributor
timestamp: October 11, 2021, 12:13:01 pm
content: Yeah USB-PD is another can of potentially flammable worms.Rather impressive that they manage to push 100W trough that little cable and connector. But given the sort of quality i seen with USB 2.0 cables does get me worried. I seen microUSB cables that couldn't even hold the 500mA without having the voltage on the end of it sag out of spec.The direction of power flow is also none at all obvious. It used to be that the host always provides power, now anyone can do anything. You can change a laptop from a USB-C charger, but then plug a phone into that same USB-C port on the laptop and charge the phone from the laptop. All while there is software in the loop of things to decide if a port is going to send out 5V or 20V or anything in between. All it takes to send 20V into a phone designed to take 5V is sending a few commands over the I2C bus for the USB power controller chip.

author: Ultrapurple
author_rank: Super Contributor
timestamp: October 11, 2021, 03:39:40 pm
content: I have a range of USB-C cables here with different claimed ratings including 3A and 5A. Is anyone interested in me X-Raying them to see how much metal they actually contain?(Obviously this won't be a scientifically rigorous market sampling, it's just for indication).

author: therwp
author_rank: Contributor
timestamp: October 28, 2021, 01:21:36 am
content: Quote from: Ultrapurple on October 11, 2021, 03:39:40 pmYes!