Design 12:1 2.0 USB Multiplexer | Matija

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Discussion Overview

The discussion revolves around the design of a 12:1 USB multiplexer, specifically using MAX4999 multiplexers, to allow individual access to multiple USB devices by a microcontroller. The context includes technical challenges related to high-speed USB signals and the practicality of using multiplexers versus USB hubs.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Matija is attempting to design a 12:1 USB multiplexer using two MAX4999 8:1 multiplexers in parallel, expressing concerns about high-speed traces on a breadboard.
  • BoB suggests using a USB hub for simultaneous access to all devices, questioning the necessity of multiplexing.
  • Matija responds that USB hubs with 12 ports are too large and power-consuming for his mobile device project, indicating a preference for multiplexing ICs.
  • BoB mentions the possibility of cascading two 7-port hubs to achieve 13 ports, providing an alternative solution.
  • Another participant reiterates the suggestion of using USB hubs, emphasizing the availability of various sizes and the importance of following layout guidelines from datasheets.

Areas of Agreement / Disagreement

Participants express differing views on the use of multiplexers versus USB hubs, with no consensus reached on the best approach for Matija's project.

Contextual Notes

Participants highlight potential limitations in size and power consumption of USB hubs, as well as the technical challenges associated with high-speed USB signal integrity on breadboards.

Stric_Matic
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Hi everyone,

I've been trying to design a 12:1 2.0 USB multiplexer for a while, with very little success. I've bought a couple of MAX4999 8:1 multiplexers, trying to use two of them in parallel such as shown in the datasheet.

I've put them on a breakout board from Adafruit, and started testing on a breadboard. I'm need at least 12 USB devices to be accessed individually as removable disks, by the microcontroller (Arduino YUN mini). One of which, for example is Mobius Action Camera.

Obviously, the first concern is the high-speed traces and if you can play with them on a simple breadboard, but I did test a single device, with lines running through the breadboard and everything seemed to work fine as long as they didn't run through the multiplexer.

Any thoughts, suggestions, criticism?

Much appreciated,
Matija
 

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Why not get a USB hub? Then they can all be accessed at the same time.

BoB
 
That's a great idea! The reason I'm looking into the multiplexing ICs is cause hubs with 12 ports are too big (I'm building a mobile device), and power consuming. But if you find one that is relatively small, please let me know!
 
they have 2 port devices as well
 
If you cascade two 7 port hubs you will get 13 ports available. 6 open ports plus the second hub in the first hub. The all 7 from the second.

BoB
 
rbelli1 said:
Why not get a USB hub? Then they can all be accessed at the same time.

BoB

I agree

Stric_Matic said:
That's a great idea! The reason I'm looking into the multiplexing ICs is cause hubs with 12 ports are too big (I'm building a mobile device), and power consuming. But if you find one that is relatively small, please let me know!

what you are trying to do isn't likely to be any smaller
 
Stric_Matic said:
But if you find one that is relatively small, please let me know!

Just google USB hub. You will find all different sizes and shapes. You can also get the hub chips that are not much bigger than the multiplexer you are looking at. Pay very close attention to the layout guidelines in the datasheet and application notes.

BoB
 

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