Actions
Forum Thread Details
  • State Not Answered
  • Replies 6 replies
  • Subscribers 56 subscribers
  • Views 555 views
  • Users 0 members are here
Related

Need a 4 channel multiplexer with a loooot of inputs...

Former Member

I'm designing a cape for a BeagleBone and I'd like them to be stackable. For this reason, I need to be able to put a cape into a particular "mode" such that the I/O goes to a different set of pins on the beaglebone for each cape. I plan to do this with a 4 channel multiplexer (I plan to stack up to three shields), but I have a total of 10 signals (possibly more later) that need to be switched concurrently. So far I've found a dual 4 channel multiplexer, but I need something that can handle 10 signals at once, not just two. Anyone know if such a chip exists?

  • 0

    Hello Riley,

    Apologize for the delay, I am moving this to the Single Board Computers area of the Community,

     

     

     

    Thank you,

     

    Jamie

  • 0 in reply to element14jamie

    Hi Riley,

     

    Assuming I've interpreted it correctly (I may have misread), I'm not sure this would be feasible, because if you want 10 pins per cape to go to different pins on the BBB, then that is 40 pins you're consuming on the BBB for four stacked capes. That is a lot of pins to configure, and your design will be very complex since you'll need an IC (or multiple) on each cape connected to 40 pins on the headers so you can perform the switching operation. Better to maybe address each cape on the same 10 pins (much like a computer data bus and a few address lines) assuming your circuitry can go tri-state.

  • 0

    Hi Riley,

    Would it be possible to design your stackable cape such that the input connector on the top is slightly offset from the output connector on the bottom? This would allow you to route the pins on each cape to different pins from the cape above and you wouldn't need any multiplexers. Put another way, every pin from the above connector would be shifted 10 pins over on the connector below.

    Doug

  • 0 in reply to dougw

    Hi Riley,

    I didn't think it all the way through. Is it possible to simply use jumpers on each cape to select different output pins? One way to do this without soldering is to connect each output to 3 pins with cuttable traces and just leave a different one intact on each cape.

    Doug

  • 0 in reply to dougw

    Douglas Wong wrote:

     

    Hi Riley,

    Would it be possible to design your stackable cape such that the input connector on the top is slightly offset from the output connector on the bottom? This would allow you to route the pins on each cape to different pins from the cape above and you wouldn't need any multiplexers. Put another way, every pin from the above connector would be shifted 10 pins over on the connector below.

    Doug

    Elaborating on this comment, BBone capes usually have through-hole stacking connectors.  However, there's nothing to stop you from using surface-mount connectors on the top and bottom surfaces and shifting signals 10 pins over between the two connectors.

  • 0

    Hi Riley,

    One other thought - the complex multiplexing function you are describing sounds like it might be suited to a cross point switch - you may have more luck searching under this terminology. There are lots of them out there, but not likely optimized for your application.

    Doug