I tried looking online, but didn’t find an answer yet – I know one of you can answer this in no time at all. I recently bought an HDMI splitter which automatically switches the input to the most recently powered / activated device. Is this how USB splitters work? If I only care about connecting two printers to one USB port, do I need an auto switching hub or one with separate on / off switches for each hub or just a passive hub?
Also, I’m assuming I don’t need a powered hub since the printers have their own power supply – is this correct?
A USB hub I a sort of networking device. It does not switch exclusively to any of the connected cables/devices, but instead dostributes traffic to all of them.
You only need a powered hub if you will be attaching devices that draw significant power from the port. Usb powered hard drives or scanners (I.e. That do not have their own power supply)
I think the limit on total USB devices is 256 at one time - go wild!
If you’re buying a hub, I would recommend buying a powered one. It’s correct that you should not need one for your printer, but it seems to me like only a matter of time before you find something that wants power.
Devices like phones, iPods and cameras may have their own internal batteries, but it’s sure convenient to have them charging over USB while you’re syncing them up.
Nope. USB does all the polling as part of the standard, so it is about a plug and play as you are going to get. I would also recommend a powered hub for things like charging devices, etc.
More specifically…the devices have addresses, and the hubs are part of the routing process. So when you print to a specific printer, the USB code effectively walks down the collection of wires, picking the correct port on each hub, until it gets to the printer.
If you print to a different printer, the hub will send the request to the appropriate port.
TL;DR: Just plug them all in, and it’ll work. No decisions to be made, outside of the powered/unpowered hub question.
Cite? My understanding is that USB hubs are no smarter than ethernet hubs, which do nothing but passively send all data all ways (just keep things clean electrically while this happens). An ethernet switch routes content according to addressing data, but it needs a fairly powerful processor (as things go) to do that - and only a router can actually make active decisions about where to send what packets.
USB is an open serial protocol, and all devices on the chain see all data. They just ignore any not tagged for them. Is that incorrect? (Looks at the tiny unpowered USB3 hub on the desktop and wonders where the switching circuitry could be.)
OK, that’s not a “hub”, but it seems that simply splitting the data does not provide full USB functionality.
This thing’s answered questions on Amazon are contradictory, so ixnay on that.
The point of my OP was asking whether something like this would require toggling the individual port switches on and off, or the device addressing would handle having two or more printers active at once. From the responses, it’s clear that multiple active ports to multiple printers is no problem.
Yes, no matter what the extended answers are, USB is just plug and go… I don’t think collisions or addressing problems exist, outside of perhaps development systems.
There’s 7 bits for the address, which limits you to 128 devices. Your computer has an address, which means that there’s 127 left out on the wire. You can’t use 0, so that leaves only 126.
As a practical matter, I’ve never seen anything more than a 16 port hub (except charging stations and those don’t count), and each hub has an address too. So if you have So if you have 8 hubs, each maxed out with 15 devices and one cable going to the next hub, you’d end up with 118 devices total.
If I did my math right, and it is late at night and I’m medicated so all bets are off. But you get the idea I hope.
Anyway, it’s not 256, but it’s still high enough that you can probably go hog wild.
These are splitters for USB powered devices, like cell phone or camera chargers. It’s only for the power, not the data. So if you have 3 things you need to charge, you can charge all 3 from one USB port (as long as you don’t exceed the total current capability of the port) but you can only actually use one device at a time as an actual USB device.
The second one you linked to (not in the quoted text above) looked to be a real 2 port hub, which is more complicated than just putting the power and data lines in parallel.
USB hubs kinda route, but it’s nothing like ethernet routing and they don’t keep routing tables or anything like that.
USB starts at the root controller in your computer. From there, you can have multiple hubs. As the hubs get farther away from the computer, those are the “downstream” hubs and devices. The ones closer to the computer are “upstream” with the host computer being the top of the upstream path.
If a message comes from the host, each hub retransmits the message on all of its downstream ports. If any device below it responds, each hub in turn then passes the message back up through its upstream port.
Let’s say for example that you have your PC, a USB port that goes to a hub, and that hub is connected to a mouse, a keyboard, and another hub. The second hub is connected to two printers. The PC is the top of the “upstream” path and the two printers are the farthest downstream devices. So let’s say you move your mouse. The mouse sends the USB message to the hub that it’s connected to, and that hub sends it to the PC, and to nothing else. If a message comes back from the PC, it goes to the first hub, which then transmits the message to the mouse, the keyboard and the second hub. The second hub then transmits the message to the two printers. It doesn’t matter which of the four devices the message was actually intended for. All four get a copy of the message. The other three just ignore it since it doesn’t match their address.
So on the upstream path, only the upstream hub and the PC received the message from the mouse, but on the downstream path everyone ended up receiving that message.
If one of the printers had generated a USB message, that would have gone to the downstream USB hub, then to the upstream USB hub (but not to the other printer), and then to the PC. The PC’s reply would then go to every device in the chain following the same paths as before.
