Been having a little trouble figuring out how to get the ASCII data read from a RFID card to transmit to the PC. I was able to initially set up the reader by following this :
http://hcgilje.wordpress.com/resources/ … tagreader/
I can detect a card being read by the LED illuminating every time a card passes by.
I have pin 7 connected to ground to set the ASCII output method.
I assumed I would want to connect pin 9 TTL Inverted to the RX of the PC. I tried to pass the inverted TTL through a max232 and still nothing.
Thanks for any pointers!
You should be using pin 8 (non-inverted CMOS) from the ID-20 to feed into the MAX232. The MAX232 converts from non-inverted CMOS-level to inverted RS232 levels.
Thanks for the help! I will try this when I get home. could there be damage done by connecting it to the 232 and directly the the RX of the serial port?
could one put a 7404 gate on pin 9 to invert it again?
Sorry for all the questions just new to this.
Thanks!
Why can’t you invert using software?
DrBoris:
Thanks for the help! I will try this when I get home. could there be damage done by connecting it to the 232 and directly the the RX of the serial port?
could one put a 7404 gate on pin 9 to invert it again?
Sorry for all the questions just new to this.
Thanks!
Why would you want to invert pin 9 again? Pin 9 is the inverted out, pin 8 is the non-inverted output (so pin 8 is an inverted pin 9).
You don’t connect the ID-20 to both the MAX232 and the PC’s RX pin. The MAX232 is a logic-level to RS232 converter. You connect pin 8 of the ID-20 to pin 10 of the MAX232. Then connect pin 7 of the MAX232 to the RX pin on the serial port of your PC. For the rest of the connections (including the caps) on the MAX232, see the datasheet.
The MAX232 wants CMOS-level serial input which is non-inverted +5v logic. It outputs the apropriate signaling for RS232 (which is inverted and ranges from approx. ± 7V to 12V depending on the device).
The reason you couldn’t get any data by simply connecting pin 9 on the ID-20 to the RX pin on your PC is because 5V is not within spec for RS232 signals.
Also -
Don’t drive a LED directly with pin 10 on the ID-20. It’s not designed to source current and many people have damaged their modules this way. Instead use pin 10 to drive a NPN transistor which powers your LED as shown in the ID-20 datasheet.
In re-reading the datasheet for the ID-20, I’ve succeeded in confusing myself. I might have pins 8 and 9 on the ID-20 backwards. They seem to be referring to pin 8 as the 5V level RS232 signal (even though they don’t come out and say this directly). This would make pin 9 the TTL-logic signal (which they call the inverted output). It’s confusing because most people would refer to the TTL output (for connecting to directly to a microcontroller) as the non-inverted output.
So if that’s the case, use pin 9 on the ID20 to connect to ping 10 on the MAX232.
Alternately, you can retry connecting directly to your serial port using pin 8 on the ID-20 (with a 1K resistor in series). It might work as many serial ports will still work with the out-of-spec 5V signal.
Here’s a better datasheet for the ID-20 than the one on Sparkfuns product page. Near the end they talk about connecting to a serial port or microcontroller.
http://www.id-innovations.com/EM%20moud … %20v22.pdf
Sorry about that last post but it seams that every time I tried to reply i had to wait to get approved… any way…
I was able to get this working thanks to etracers help.
It is pin 9 from the ID-20 to the input of the 232. A few mistakes on my part were not grounding the DB9 (p5) and the id-20 output going into the rx and not tx line of the 232.
The data sheet you linked to was much better resource than what I had. If anyone is listening from sarkfun could ya’ll add this to the product links?
this was also very helpful http://www.sparkfun.com/commerce/tutori … als_id=104