Using a USB switch for an interruptible connection?

[Ragnarokae]

Situation: Device A is connected by USB to a USB switch. The switch is connected to Device B. A needs to send information to B, but only after a certain time. For example, A can NOT send information to B for the first 30 seconds, but MUST send information after the first 30 seconds.

No connections can be manually changed or removed.

We are trying to get a button or toggle in place so that A sends information when the state of the button or toggle is changed from false to true.

Any ideas of what to buy or what to jury-rig (and how) to make this possible?

[Nate Smith]

Without going into the details of how to exactly when to control making the switch(microprocessor choice, etc.), your USB cable consists of 4 wires, +5v, d+(data positive), d-(data negative) and ground. Depending on what device A is, if it has any sort of "bootup" time, you may not want to use the power lines as your "switch". What I would recommend is a DPST relay(something like this) connected to the d+ and d- lines on the USB cable. Then, through your choice of control methods, turn the relay "on" at the end of that initial 30 second period, thereby connecting d+ and d- between devices A and B. You may have to experiment with the timing for when to switch the relay on, as there may be a delay after the devices are connected before they each realize that the other is there.

Hopefully this helps somewhat, I can provide more details if you are interested.

[Jeff Pahl]

It really depends on what data rate you need to support.

Is this a USB 1.0 application or a USB 2.0 application? To maintain a high speed 2.0 application will most likely require an integrated circuit solution, a slower speed application should work fine with a relay as Nate explained.

If you need to go to a high speed integrated circuit solution, Digi-Key has a bunch of chips in the $2.00 range. But they are all surface mount...

[Mike]

On an aside, thats a beefy relay you got referred to. You may be able to find something cheaper/lighter without a 5 ampere rating.

[Nate Smith]

Originally Posted by Mike

On an aside, thats a beefy relay you got referred to. You may be able to find something cheaper/lighter without a 5 ampere rating.

Yeah, I basically just did a search for DPST relay, and picked one of the first ones that came up...was just meant as an example of what kind you would need, and not a recommendation of that relay in particular.

[Al Skierkiewicz]

Jeff,
Would a CMOS switch have an application here? Something like a 4053...

[Nemo]

Thanks for the quick replies, particularly the suggestion to use a relay. We're going in that direction.