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USB/Serial Dilemma... — Parallax Forums

USB/Serial Dilemma...

starionstarion Posts: 27
edited 2011-05-11 10:31 in General Discussion
I have been working on some projects where the devices output in serial, some in USB.

While there appears to be no shortage of devices that will take serial to Ethernet usually pretty inexpensive (<$50), there seems to be a lack of devices that will take USB to ethernet. I have found a couple of 4-port USB to ethernet devices for much higher prices, but this is way overkill for what I need. A one-to-one would be fine.

Can someone provide a quick comparison of the two technologies and suggest if there is a simple inline way to convert from one to the other. Or are there limitations in doing this that I'm missing?

Or maybe I'm just not looking in the right places for a product that is already out there...

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2011-05-11 09:07
    Your problem is that USB and Ethernet are not monolithic protocols. In many ways, they're like a wire that can carry different kinds of signals. Serial to Ethernet converters take a specific kind of signal (bidirectional asynchronous serial with flow control signals) and transport it over Ethernet to a particular kind of Ethernet "socket", usually a Telnet port. Similarly, the USB clients that Parallax uses (chips made by FTDI) take a bidirectional asynchronous serial serial with flow control and transport it over USB to the USB host (your PC) using what's called Serial Port Protocol (SPP). There are lots of other protocols for other purposes. As you've noticed, there are even some devices that take all the interactions that make up USB and package them up into packets of information that get sent out via Ethernet to a matching device somewhere. Similarly, there are USB Ethernet "dongles" that are used to allow PCs that have USB, but no Ethernet interface to connect to an Ethernet network. All the Ethernet data is sent over a USB "wire" and the "dongle" translates back and forth.

    That said, what do you really want to do? What kind of data do you want to send? If it's mostly asynchronous serial ("serial port"), you'd use USB to serial and Ethernet to serial adapters and hook them together on the serial end, but it all depends on what you're trying to do.
  • starionstarion Posts: 27
    edited 2011-05-11 09:17
    I guess one of the things I'm concerned about in designing is that I feel like there is a tendency for the devices I need to use to start leaning towards USB vs. serial. For instance, we design software to handle input from bar code readers that are remote. A lot of bar code readers are going USB for use at the PC. There are several other types of "input" devices as well that we want to use that don't even come in a serial version anymore.

    So I'm just trying to stay ahead of the game in terms of technology and what I will likely have to deal with to keep on designing remote read hardware.
  • LeonLeon Posts: 7,620
    edited 2011-05-11 10:31
    A single XMOS chip could handle high-speed (480 Mb/s) USB to Ethernet comms. Both sets of code are available, and it should be quite easy to integrate them. I've actually been thinking of having a go at it. I think this would be the cheapest and simplest way to do it.
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