STAMP 2 Serial Confusion

Keith Riley

I have the Basic Stamp 2 Carrier board. I want to do real-time communication but have seen some references to the effect that this is not possible on this board. Why is that so? Is there anything I can do (cutting traces, installing a switch, etc) to allow both programming and real-time?

I really just need to receive on the Stamp, but send/receive would be a bonus.

Finally, (separate question) What would be required to be able to run the debugger WHILE I perform real-time communication? Is there a way to connect a second PC port via one of the parallel inputs? What would be required for that?

Thanks very much,

Keith

Jon Williams

If you want to debug your BASIC Stamp code while it is doing serial communication on another port -- you need to add the other port. This will require 2 or 4 pins -- 2 for simple (TX and RX) and 4 for comms with flow-control. To connect a second port you'll need an inverter like the MAX232.

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Jon Williams
Applications Engineer, Parallax

Keith Riley

Jon,

Thank-you for your prompt reply. One remaining question. If I don't mind sharing the one port alternately for programming and real-time, are there any limitations with the Stamp 2 Carrier board for Real-time? Seems like I caught some reference to issues with using the carrier board for real-time....

Thanks again,

Keith

Jon Williams

Older versions of the carrier board did not have the caps we currently use between the PC's DTR pin and the Stamp's ATN pin (pin 4 on the module) -- see attached schematic. Some terminal program, notably Hyperterminal, keep the DTR pin in a state that would put the BASIC Stamp in reset without these caps. Of course, if you want to use the Debug Terminal window (you can open it manually in the BASIC Stamp editor) to do your "real time" communication, you won't have any problems as it keeps DTR in a state that won't reset the BASIC Stamp.

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Jon Williams
Applications Engineer, Parallax

Post Edited (Jon Williams (Parallax)) : 6/9/2005 2:01:25 PM GMT

Keith Riley

Jon,

Thank-you. The Max-232 looks like a perfect fit. Can you recommend a site where I can order this part in small quantities (1 or 2)? Most of the sites I found are more interested in thousand quantities.

Tahnks,

Keith

Chris Savage

Keith,

·· Try Digi-Key or Jameco.· I have purchased from both.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Forrest

glitchbuster.com/ is my favorite place for small quantities. They sell the MAX232N for $.69 and 50V 1UF electrolytic capacitors for $.09 each (you'll need 4 with the MAX232N). Add $1.85 for postage.