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I have a system where there is usb slave device that is in a rotating structure behind a slipring. I need to pass the signal through the slipring (we only have 4 "wires") and onto a computer. Due to the long distance and noisy environment I'd like to convert the usb signal to rs232 or 485 but my understanding is that usb to rs232 dongles do not work on slave devices.

Does anyone have an idea as to how to do this? There are usb to cat5 but I only have four conductors.

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    \$\begingroup\$ why wouldn't a usb to RS232 device work? There is no reason why not. \$\endgroup\$ – KyranF Mar 17 '15 at 20:08
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    \$\begingroup\$ Because the device is a usb Peripheral, not host. \$\endgroup\$ – Passerby Mar 17 '15 at 20:25
  • \$\begingroup\$ Exactly the Peripheral has no idea about an FTDI chip or the equivalent \$\endgroup\$ – Ross W Mar 17 '15 at 20:26
  • \$\begingroup\$ Even if you will manage to find usb-serial converter for the device, it won't help, since (probably) your device is not using simple serial protocol, but is using some specific USB profile, right? \$\endgroup\$ – Eugene Sh. Mar 17 '15 at 20:43
  • \$\begingroup\$ How long is your line? The best thing you can do is to use some USB repeater there are some cheap ones out there..). EDIT: Oh..missed the slip ring part.. \$\endgroup\$ – Eugene Sh. Mar 17 '15 at 20:46
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I don't think this is straightforwardly doable, the speeds are too different. Best you could manage is:

  • put a microcontroller in host mode on the slave side
  • write drivers for the USB device
  • write a serial protocol for the actions you want to perform
  • have the PC communicate with the microcontroller over the slip ring.
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I'm not aware of any COTS solutions, but there are many chips that can function as a USB host and also have a UART interface. The FTDI Vinculum is just one example, but there are many others, including the Microchip PIC32, or indeed, pretty much any microcontroller with a USB host or OTG hardware interface.

Such a device could be programmed to act as a host to your USB peripheral, and then communicate using UART protocol through the slip rings to a standard USB-to-UART adapter attached to your host.

If this is a one-off project, you could even use a board-level product such as RaspberryPi or BeagleBone to perform this function.

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  • \$\begingroup\$ This was my backup plan. Use a Pi to collect the data on the USB Peripheral and then send it out over RS232. Doesn't look as if there is an OTS solution (google hasn't shown anything) \$\endgroup\$ – Ross W Mar 17 '15 at 21:11
  • \$\begingroup\$ There are smaller and slightly cheaper solutions than a $25 dollar pi. But that's pretty cheap \$\endgroup\$ – Passerby Mar 17 '15 at 21:53
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I have put an USB camera in the squirrel house in my garden. It connects to my PC via an USB-over-UTP converter set (UTSP cable length 30 meters or so). Something like this

enter image description here

But I think it requires 8 (or maybe 6) wires, not 4.

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