Physical Computing

A few things to check if the stamp programming application won't recognize your stamp. These are tips gleaned from past classes, the stamp mailing list, and the tech support staff at Parallax. These notes assume you're using the Stamp Windows editor, version 1.091b or later, and a programming cable made according to the Parallax stamp manual instructions, and you're using a BS-2, not a BS-2SX. Also, it's wise to remove your stamp from any circuit you've built and check it on a bare protoyping board. If it works there, you know the problem is in your circuit, not the stamp:

1. Power and ground: Are you putting the proper DC voltage in pin 24? is pin 22 grounded properly?

2. Stamp voltage regulator: when you power up the stamp, do you get +5V out from pin 21? If not, the stamp's onboard power regulator may be blown. It can be replaced with an external 5V DC regulator.

4. Is the serial programming cable working? To check, open the debugger window in the stamp II windows editor, and click the RTS checkbox. The DSR light should light up underneath it. Also, if you type in the text portion of the window, you should see the text as you type it. IF either is not true, your cable could be the problem. Check to see that it's built properly and all connections are solid.

5. When the stamp is powered properly, and connected via the programming cable to the Windows programming interface software, you should get the following voltages on pins on the stamp. Use pin 23 for ground, assuming it's properly grounded. These pin numbers are the physical pins of the stamp, not the in/out pins. Remember, the physical pins are numbered in a U-fashion, starting at the top left hand side of the stamp:

6. On the stamp, there is a brownish chip on the right hand side about midway down. This is the resonator for the PIC processor that is the heart of the stamp. There are three metal strips running down the resonator. The center strip is ground, and between it and the others, you should be able to read +2VDC.

7. Failing all else, you should check to see if the stamp can be recognized by an earlier version of the stamp programming interface. Use the stamp2.exe program, available from the Parallax web site. Restart your computer in DOS mode, and try to identify the stamp (Alt-I in the stamp2.exe program). If it can be recognized, try writing a simple program for it in the stamp2.exe application.

Worthwhile also to check your prototyping board for shorts. We've seen the problem crop up where a screw in the prototyping board caused a short between power and ground.

When you've tried everything and still can't get the stamp to be recognized, contact Parallax tech support. They're very helpful and understanding, and will arrange replacements for problem stamps.

Stamp Troubleshooting