RFID interface... am I missing something?

EB

I am trying to get a Parallax RFID reader module to work with a Propeller (using the Propeller Proto board). I can toggle the enable line and see the LEDs on the board change from green to red, but it appears that the RFID module is dead, because watching the serial out from the RFID on an oscilloscope, it just says high (5V) all the time - no serial data appears to pass.

Answering some of the troubleshooting questions that might come up:
Q: Do you know that the RFID tag is good?
A: It was as of last week, we had the reader hooked up to a BS2.

Q: Is the Propeller pin for the serial data configured as an input?
A: Yes. And the RFID module's SOUT doesn't flow data even when that pin isn't connected to anything on the Proto board.

Q: Are you sure your oscilloscope is setup to see transitions on the serial line?
A: Yes. I've been using this particular scope for several years now, and have on many occasions used it to watch serial data.

Q: How is the RFID module being powered?
A: It is tied to the 5V and GND off the regulator on the Proto board. It appears not to be pulling the rail down, as it contiues to measure 4.99V even when the RFID module is enabled


So my question is this: am I missing something? Or is my RFID module dead?

Thanks in advance!

Mike Green

I've used a Parallax RFID Reader module with a Propeller and it worked fine for me. Since the RFID module has a 5V logic output, you need a resistor (like 1K) in series with the serial output of the RFID module, otherwise the 5V signal will damage the Propeller which operates with 3.3V logic levels. That wouldn't affect the RFID module though. The /Enable input doesn't need a resistor because it's an input to the module and the 3.3V logic signal from the Propeller is adequate to trigger the module.

So, I don't know why your RFID module would appear to be dead. There's nothing obvious that you've described that would account for the behavior you're describing. I know that you may have damaged your Propeller.

EB

I did briefly (2 minutes total, perhaps, spread out over an hour of a few seconds at a time) run the serial out from the RFID straight into the Propeller. Since then, I have been running it through a 1k resistor.

However, even with the SOUT disconnected from the Propeller, I still don't see any data on it when I put the tag up to the antenna.

Mike Green

The only thing I can suggest is to call Parallax's Customer Service people on Monday.

bambino

Is it possible to hook the unit back up to the BS2? It would give you some more insight!

EB

Sadly, the BS2 board is in a zillion pieces that are presently being reassembled for the Propeller. Possible, but quite a large amount of work. The more we've messed with it though, the more convinced we are that the RFID module is toast.

Chris Savage

EB,

Just as a note there are only 4 connections to be made on a Board of Education to test the RFID Reader. Two are for power and two for I/O lines. It’s pretty quick to test an RFID Reader on that board if you have it.

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Chris Savage
Parallax Tech Support