So now its working but with annoying bugs, please help!! PARALLAX RFID READER

eternalist

TO Jim,
Thanks so much for those links! I owe you tremendously for setting me on the right path!!!! I used the VB program and finally realized that I needed to use PORT 1! I was just trying 4 or 5 which are listed as the 'virtual' COM ports. I guess 'virtual' is the key word. I was so hyped to get ANY response from my computer! So really, thanks!

Alright, but now I have three new problems with my RFID Reader if anyone can help.

1. When I scan a transponder I get a weird output to the screen i.e: 'FPuP??FdF3525' <--- this is just an example from memory but I know there should not be question marks in the key codes. Also, if I scan the same card numerous times I will get slightly different outputs? WTF. However, when I used the reader in hyperterminal I did get 'normal' key codes with no question marks. again, WTF!?

2. After I've scanned about 4 - 5 codes the reader seems to jam up and not work unless I unplug it and the close & open the port. I'm using a power converter that plugs into the wall that I salvaged from a router. Its 5 volts and .4 Amps, could this be too much for the RFID card?

3. Due to the previous issues I decided to build the more advanced schematic that has the 'DTR (Data Terminal Ready)' Option but when I choose enable the reader goes green (meaning its not reading) and when I choose disable the reader goes red and is ready to read. So in otherwords, its like its working backwards. When I choose to connect the reader closes down and when I disconnect the reader powers up. I'm nearly sure I just have something backwards but I've tried to check everything. According to the schematic the emitter on the 2N3904 transistor is connected to a ground but its not connected to the negative of the battery. In my previoius post I explained that I'm fairly new to electronics , especially building circuits so in this case what should the emitter pin be attached to (In layman's terms). Also, another possibility Parallax says to use a NPN 2n3904 Transistor but should I be using a PNP 2n3906?

THIS IS THE LINK TO THE SCHEMATIC FOR THE INTERFACE I BUILT

Franklin

No link and no code. Both would be helpful.

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- Stephen

eternalist

Sorry, the program I'm using is at this link

http://forums.parallax.com/showthread.php?p=727719

and the schematic for the interface is

http://forums.parallax.com/attachment.php?attachmentid=46147

Chris Savage

Well if it works with Hyperterminal then there is some issue with the RFID Software, which could be related to not having the latest .NET updates and service packs on your PC.

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Chris Savage

Parallax Engineering
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eternalist

Well...saying that it works in hyperterminal is not exactly accurate. First off, I built two separate interfaces using the schematics that I think you personally posted (Great job by the way!) and the first was the one that does not have the 'Data Terminal Ready' option on it. For this one I got output from hyperterminal but it was still plagued by the issue of being very intermittent and eventually needing to be powered down and reset after about 4 / 5 scans. Also, I would put the transponder in front of the reader and nothing would happen so I would leave it there a few seconds. Next, tons of key codes would come rushing to the screen all at once. These are problems I've had with both schematics. However, I was so hyped and excited that I nearly soiled myself in wake of my tremendous electronic victory. Thus these problems were not important to me at the time. It was only later after the silent fanfare and fist pumping that I realized that I want this thing to work like clockwork so I can create a reliable project from it. After building the first schematic I decided to take a go at the more advanced one w/ the DTR function. I turned on the song 'Eye of the Tiger' from Rocky and began to build. The specific problem I'm having with the DTR enabled inteface is that when I disconnect in hyperterminal the reader is powered on and ready to read (LED is RED) but when I connect in hyperterminal the LED goes green, thus the reader is off. Essentially its like the function is reversed. I may be confused about specifically where to connect the emitter pin on the 2N3904 NPN transistor. I see that its grounded but in layman's terms where do I connect this to? The casing of the DB9 Connector? The (-) terminal of the battery? Thanks to everyone who previously gave input, you guys are geniuses'!!

-- BEn

THIS IS OBVIOUSLY THE SCHEMATIC I ATTEMPTED TO BUILD

http://forums.parallax.com/attachment.php?attachmentid=46147

Unsoundcode

Hi eternalist , the circuit you referenced in your last post should work .

Your question about the emitter of the NPN 2N3904 , this should be common to pin 5 of the DB9 connector and the GND of the RFID connector , the GND of the RFID connector should have the negative wire connected from your power supply. In this particular instance it might be easier for you to think of the GND connections of the schematic as being negative connections.

Your circuit contains the DTR enable/disable option (Q2) , its important that whichever terminal program you use has control of the DTR signal or your RFID may not work correctly. I am unsure whether you have this option under Hyperterminal but the Parallax RFID software does and should work with your reader.

Try and verify the RFID is reading to begin with , use the two transistor interface that you built and double check the placement of parts and the integrity of the solder joints. Take a piece of wire and jumper the /Enable pin of the RFID connector to GND (negative). This will permanently enable your reader , now you can use any terminal program set at 2400 baud rate to test incoming data.

What I would look for now is repeatability using just one tag·. Depending how the terminal program you use is set up it could be possible to receive a ? displayed on the screen. Try this with one tag and record the results exactly so that you can post them back here. Vary the distance and interval between swipes , see if anything works .

Jeff T.