USB Network

[timyhac]

Hi everyone,

I have a need for a system which provides USB connectivity to a network of identical devices. The layout of the network is attached to this post.

It need to design a single device that can be manufactured multiple times and connected with each other. It needs to do the following things.

• Use USB connections.
• The root controller is a computer.
• Map the network ( which device is connected to which )
• Connect multiple devices together in a user-defined configuration.
• The device can be powered so it's not drawing a hundred million Amps from the computer.

There are several connection cases:

If the usb connection comes from

1. The bottom -> The device needs to use the connection internally, and provide a usb connection to the top and left.
2. The top -> The device needs to use the connection internally, and provide a usb connection to the bottom and left.
3. The right -> The device needs to use the connection internally, and provide a usb connection to the bottom, top, and left.
4. Alternatively, every connection can be used as both an in and out.

My first thought was to use a normal usb hub but I realise that wouldn't work due to its single input.
If any of you guys have an idea about how to do it I would appreciate it a lot.
Also, I think this network type would be quite useful especially with the advent of wireless USB and other such technologies.
Thanks!

[blueroomelectronics]

What would be the practical use of such a device? Modern PCs have a dozen USB ports and port extenders are common. Also USB is not very long range and requires intelligent controllers.

[timyhac]

The reason I don't want them all individually being hooked up to the computer is basically for cable neatness. Also, I want the layout of the network to be mapped automatically so this wouldn't be possible with them all individually being connected to the computer's USB controller.

[Papabravo]

I don't think it is possible to "map the network" using USB in that fashion. In the enumeration process there is no concept of physical topology. Have you read the USB specification? Did you understand it?

[timyhac]

I have not read the entire USB specification, but I do understand that there is no concept of physical topology in the USB specification.

I also understand that my application would require more than the ordinary USB controller - hub - device configuration.

I just want the device to be really intuitive to use. EIther the user can plug it into usb directly into the computer root hub via a cable. Or they can connect any combination of the devices into each other. The computer would map their interconnections and provide the normal usb interface to each of them.

Is there any other interface (besides USB) that I could look into using?

[Papabravo]

RS-485 would support the type of topology that you drew. I still don't know how you plan to "map the network".

[AlexR]

USB is a bus technology, it is not a network technology hence it needs no mapping. As long as there are less than 126 nodes connected to any USB host and the USB host can see all the nodes without any routing loops then it should work fine. In fact daisy-chain connections of USB devices was quite popular in the early days of USB before USB hubs became the standard way of providing extra USB connections.
You might however need to re-arrange your node topography to get rid of the nodes with multiple outputs since that makes them hubs.