RFID Proxmity Circuit

hmm, are you sure the power connector is + tip and outputs DC? Sometimes they are sneaky and can output AC and/or have a - tip connector on them.

what about the tags... do you have more than one tag or just one? are you sure the tag battery is good and inserted in the correct polarity?

I just used a standard 9v barrel plug AC/DC type adapter with a positive tip (the inside conductor is positive).

have you already tried connecting the reader board to the stamp? if so its possible the stamp and/or the reader may have been damaged.

also are you using the proper power supply and do you have active tags (with batteries installed) in the area? the reader won't do anything unless there are tags around for it to read. there are no commands or a prompt or anything, it just kicks out tag IDs when they are in range.

I just connected it up to the RS232 serial port on my PC, opened hyperterminal, and set it to the correct COM port in Windows for that hardware serial port.

Hi Jeff,

You're going to need to figure out a way to get the TTL level serial data out of the RF9315R reader. The RS232 specification is not compatible with the STAMP (or just about any microprocessor), which is expecting TTL serial communication.

From http://answers.yahoo.com/question/index?qid=20090211134205AApzAvY
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TTL is typically used within a single system, such as within a computer, and generally does not leave the system enclosure. When one device within the box needs to talk with another device (e.g. a CPU needs to talk to a hard drive) TTL would be appropriate. It uses voltages in the 0V to +5V range. TTL can be very, very fast, but can only travel a short distance.

RS232 (I believe it means Recommend Specification #232) is a spec for communicating between different systems. It is specifically designed to leave the system enclosure (e.g. a computer needs to talk to an external modem). It is far slower than TTL, but can also go long distances, up to 300 feet and beyond I believe. Its voltage is range +/- 15V.
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But you do have some options;

1) Find the TTL level data as it exists on the reader board before it gets converted to RS232 levels and tap the TX/RX lines over to your STAMP.

2) Purchase or build an RS232 to TTL converter. The Parallax site has a whole section on various converters you can build fairly cheaply, including one designed for use with serial RFID readers.

3) Use the RS232 port on the STAMP. This can be done, but it is not "ideal" and is not normally supported. The RS232 port on the STAMP is there for one reason - programming your STAMP with a PC. Unfortunately I can't remember the code tricks you need to use to access the RS232 serial port during runtime operation.