Wireless USB and Virtual Serial Ports

John R.

Silex has an interisting product, an 802.11g wireless USB Device Server, see: http://www.silexamerica.com/us/products/network/usb/sx2000wg.html

It does not (understandably) support "isonchronous" devices (speakers, web cams, etc.).

My question is, are the virtual serial ports (e.g. Stamp, USB2SER, Prop Plug, PSCs, etc.) considdered "isonchronous" USB devices?

Or more directly, would this device work for communication with a STAMP/Prop/SX/PSC, etc.?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
John R.

8 + 8 = 10

Chris Savage

John,

I think you mean, “Isochronous” (no ‘n&#8217[noparse];)[/noparse]. In any event this is the very problem that exists with many USB to serial adapters now, poor timing control of the handshaking lines and/or latency issues. The BASIC Stamp requires somewhat accurate timing during the identify and program sequence which I believe would be inhibited by this device. Take care.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support

John R.

Chris;

Thanks for the information, and yes, I had a typo with the extra 'N' the first time through, and then managed to be consistent

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
John R.

8 + 8 = 10

Mike Green

John,
You'd have to distinguish between communicating for the purpose of programming vs. communicating for the purpose of control input/output.

None of these wireless devices are likely to work reliably for programming because of the timing issues that Chris touched on. To insure that there really is a functioning Stamp or Propeller on the other end, the Stamp editor and Propeller Tool converse with the device on the other end and need to get the right responses. These are carefully timed on both ends and don't work reliably if there's too much delay in the connection. Also, the Stamp and Propeller use the DTR line to force a reset which starts the boot loader and many wireless links (and USB-serial adapters) don't implement these control lines properly.

If you don't need programming capability, any of these wireless links can be used to communicate with a running program in a Stamp or Propeller (or SX for that matter). I happen to have a Propeller running a simple Basic interpreter. The interpreter gets its commands and programs over a wireless serial channel using two xBees, one plugged into my MacBook (running Windows XP). The built-in USB-serial adapter can be used, but may force resets when the serial port is opened. This is its normal behavior even with a wired serial port as DTR is toggled.

John R.

Mike;

Thanks for confirming, that's about what I gathered, that it may work for communication, but not for programming. I've got an e-mail in to the manufacturer. They make it sound like the device may not even establish a connection if an isocronous method is called for. When (if) I get a response, I'll post the answer here.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
John R.

8 + 8 = 10