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Thread: 3-4 Arduinos 10Meter USB cables, Vixen Freezes

  1. #11
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    Default Re: 3-4 Arduinos 10Meter USB cables, Vixen Freezes

    One thing of note with arduinos is that the arduino is a development platform, not a light controller. The whole point of the arduino is to learn microconroller programming. It's designed to be used on the bench, next to the computer. It's intended that you understand (or are learning) the code in the sketches you're creating. I bring this up because all too often, people will buy an arduino, and some accessories to make it control lights, then find some sketch on the internet and think it's a lighting controller. Can it work? of course it can. Is it the best solution to get the job done. No it's not.

    USB is a desktop data transfer technology. It's designed for short data links from a PC to a printer, or mouse or whatever other little computing gadget is on your desk. It's not designed as a transmission protocol. It's intended to be used at around 3 meters or less. Sure there are longer cables out there, and they'll work on for some applications, but not for others. There's extender technologies out there, some are active repeaters, some are balun type converters to extend via some other cable type like cat5. THese can work too, but usually with some tradeoff.

    WHen using the USB as a communication method during a light show, you're actually transmitting serial data over a USB link, and the arduino has a chip on it to convert this USB stream to TTL level serial. In most cases if you plan on extending this signal beyond the desktop, you're better served by moving the USB to serial conversion close to the computer, and run the long line using a serial technology that's meant for transmitting distance. RS-232 for lengths up to 50' RS422 or RS485 for lengths longer than that. You'll then need to convert whichever serial transmission type you're using to the TTL logic the arduino chip needs at it's input. This is the same concept at play with real controllers like DMX and Renard controllers.

    When you have data transmission issues between the PC and the USB to Serial converter (built into the arduino) it's effectively the same as unplugging it from the computer. Windows will drop the device, and it may or may not reconnect. But due to the nature of virtual com port drivers, when they reappear, they need to be reopened by the software. There's no mechanism for this to happen automatically, so you need to restart the app that's using it.

    As mentioned earlier, arduinos appear to the PC as a Virtual Com Port. Since they have no unique identifier, the com port numbers are assigned in the order they connect. So it becomes very difficult to guarantee that you have the right com port configured for the right controller in the software. Com ports (and virtual com ports) are a very old technology that's not often used these days so it's not something that gets a lot of attention from OS makers like Microsoft. Usually if someone is using it, they're only using one, and they know what they're doing with it. If your display is growing to multiple controllers, you're beyond tinkering and should seriously consider using equipment better suited for the purpose.

  2. #12
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    Default Re: 3-4 Arduinos 10Meter USB cables, Vixen Freezes

    Okey
    Thanks Kevin. I did not know that we could assign USB ports. Almost like an IP address. I'm going to try

  3. #13
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    Default Re: 3-4 Arduinos 10Meter USB cables, Vixen Freezes

    Quote Originally Posted by Wali View Post
    Okey
    Thanks Kevin. I did not know that we could assign USB ports. Almost like an IP address. I'm going to try
    We don't necessarily assign the ports, the computer assigns the ports.

    My laptop had 2 physical USB ports. I had 3 MEGAs connected to my laptop via a USB hub and 1 MEGA connected directly to another USB port.

    As I configured each on in the Generic Serial Controller dialog box, the port was identified. I had to make sure to plug each Arduino into a physically different port and to make sure that if ever removed that I put them back into that same port. In other words, each one had to be plugged into a specific USB port on the computer/USB hub.

    I have not run the USB connections for a few years now due to converting my Arduino MEGAs to wifi.
    Last edited by kev; 12-17-2020 at 11:54 AM.
    Kevin

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