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Thread: Does this device exist? (see illustration)

  1. #1 Does this device exist? (see illustration) 
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    I'm trying to build my own device, and program it from Visual Basic via a USB port. But I don't want to use a pre-packaged controller board like Arduino because they don't have enough ports and all I really want is a switchboard I can control via USB as shown in the graphic. Does this exist? Can I build one? Ideas?

    usb_switchboard.jpg


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  3. #2  
    Brassica oleracea Strange's Avatar
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    How many ports do you want?

    The Raspberry-Pi has up to 17 GPIO pins available: RPi Low-level peripherals - eLinux.org

    If you can't find an existing device with enough GPIO pins, then you could see if there is some sort of "IO expander" module which will supply more (I would have thought this was quite a common requirement).

    Or you might have to build such a thing yurself. For example, you could use 7 IO bits to select one of 128 outputs and then the 8th bit to turn the selected IO bit on or off. You might even find a market for this!


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    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  4. #3  
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    Good idea on the 7/1 bits. I would ideally have 100+ outputs/switches, and I haven't seen anything close to that. I'm a developer not a circuit guy, so where I get stuck is parsing the USB data into separate ons/offs. Will I need a PIC for this? What's the simplest way to build this assuming the device never needs to communicate back to the host?

    I thought about tearing apart a USB speaker and intercepting its data for this use, then using audio drivers to code it. Hmmm....
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    Brassica oleracea Strange's Avatar
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    It is so long since I had to actually build anything like this, I don't what the easiest approach would be nowadays. I would have used discrete 74xxx series logic devices. Nowadays it is probably easier to use a CPLD or FPGA ...

    This might be useful: How-to: Programmable logic devices (CPLD) - Hack a Day

    Maybe you need to partner up with a hardware guy?
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  6. #5  
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    I'd love to..... can you recommend anyone? I asked the guy at Home - WFFwiki but I'm sure he gets emails all week long from people like me!
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  7. #6  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by haugeb View Post
    I'd love to..... can you recommend anyone?
    Sorry, I'm afraid not. There are probably more specialized forums where you might have more luck... (and before you ask, no I don't know any )
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  8. #7 Possibly 
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    Hi,I'm new here so please go easy on me.What you describe is fairly trivial to build, or depending on the definition of "large array" is buyable off the shelf. I am a moderately experienced "hardware guy" and research physicist, and depending on your budget would be really happy to help you with this. Would need to know more things, like what switching frequencies you need, whether you want the outputs buffered etc etc. As far as programming it in VB, I have no idea. My expertise is only in c++, python, Octave and some others. The way I would implement this (unless some ridiculously high frequency switching was needed) would be a USB-serial (UART) interface interfacing to a cheap micro + a CPLD. I assume there's a fairly simple way in VB to access a serial port, or if not suitable libraries are available.cheersDan
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