I just received an RFID reader from Parallax (#28440) to play with, and am having some problems getting it to send me data. I'm interfacing it with the mbed microcontroller that I also just received.
The RFID reader interfaces via RS232 (5V level), so that matches my mbed serial port perfectly. I have written test code on the mbed side so I know my RS232 code works. However, whenever I send commands to the reader (e.g. "!RW\x0F"), I get result codes that aren't even in the documentation. Specifically, most of the time I get back 0xE1 or 0xF8, when the actual result codes should be something like 0x01 - 0x07.
What's annoying is that their documentation doesn't give any timing tables, so I'm just guessing when I send all of the data at once and read immediately. I've tried different time delays, and nothing works.
I am powering both mbed and RFID reader from the USB port. Since USB supplies 500mA without external power, and the mbed uses 100ma and the RFID reader uses < 200mA, I figure I have plenty of headroom. Perhaps tomorrow I should hook up the lab supply.
Has anyone here used this reader with reasonable success?