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View Full Version : Driving USB Devices From A Stamp



John Burrow
11-19-2009, 07:41 AM
In sure this subject's been covered before, but I can't find it, so apologies in advance.

I have a several·USB devices that I'd like to·connect to·my Stamps. Obviously, these devices were originally designed to be connected to PC. They·have independant power supplies.

Most of the interface boards that I have seen, like USB2SER, appear designed to connect Stamp and PC.

Do I need an interface board·between my Stamp and·my USB devices?

Or can I mix·the 5 volts of the Stamp and the 3.3 volts of USB?

Thanks, John Burrow
San Diego
Trying not to let the smoke out

Mike Green
11-19-2009, 10:44 AM
There are two kinds of USB things ... hosts and clients. A PC is a host. A USB2SER is a client. A host can play host to one or more clients. A client is associated with precisely one host, period. A Stamp cannot serve as a USB host or USB client although it can be connected to devices that can serve either role. The Parallax Memory Stick Datalogger, by virtue of the Vinculum chip that controls it, can act as a USB host for a USB memory stick or some other USB devices (like a keyboard or mouse).

Note that USB clients expect to see 5V supplied by their USB host. USB hosts have to have a 5V power source so they can pass on the 5V power to their clients.

John Burrow
11-20-2009, 08:16 AM
I appreciate your explanation·Mike.

Are you aware of anyone that has successfully·used a DataLogger to·send/receive to something other than a memory stick? Or do I have to buy one and experiment?

Thanks, John

Mike Green
11-20-2009, 08:46 AM
I don't remember anyone here talking about having interfaced arbitrary USB devices using the Memory Stick Datalogger, but it's just a Vinculum chip and the manufacturer has examples in their documentation for things like mice and joysticks. Check out the firmware manual on Vinculum's website. The main problem will be finding documentation about the internal registers of whatever device you're planning on using since you have to know that sort of stuff.