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Hi everyone, i need your help please about usb RFID =) — Parallax Forums

Hi everyone, i need your help please about usb RFID =)

FerienhenriFerienhenri Posts: 6
edited 2012-04-15 09:00 in General Discussion
Hi everyone, =)

I am going to present myself. My name is Henri and I live in France near Paris in the suburbs. I am twenty years old and I am preparing an engineer exam.
I am studying mathematics, physics, mechanics and electronics at my school. After I graduate I will be able to obtain a place in a engineer school.

Among my different exams, I also have an oral exam where I must choose a technical subject and I will have to present it before a jury.

I have chosen to study RFID because it's very interesting to study data transmission thanks to magnetic field.

I use USB RFID Parallax 28340 device to try to measure Amplitude Modulation but I have some issues.

My aim is to visualize data transmission on an oscilloscope and mainly Amplitude modulation
I thought that I would visualize data transmission on 12, 13 ( may be 6) EM4095's pin it's not the case...

Have you ever tried to visualize data transmission or Amplitude Modulation ?
Could you explain to me how did you do ?

It's very important for me because if I want to obtain a good engineer school, I must succeed.

When I place myself on 12, 13 or 6 EM4095's pin, I thought that i would see a signal.
The best would have been Amplitude modulation.

Thanks you so much for your answer ! =D

Henri

Datasheet EM4095: http://www.emmicroelectronic.com/webfiles/product/rfid/ds/EM4095_DS.pdf

Comments

  • LeonLeon Posts: 7,620
    edited 2012-04-14 10:01
    You should see a modulated signal on pin 3 of the EM4095.
  • FerienhenriFerienhenri Posts: 6
    edited 2012-04-14 10:27
    Thanks you so much !

    Is it difficult to see this modulated signal or rather easy ?
    Have you ever seen this modulated signal ?

    What is the role of the pin number 12 and 13 of the EM4095 ?
    I thought that the clock frequency is the same as modulated signal, i have right ?

    thanks you very much ! =)
  • LeonLeon Posts: 7,620
    edited 2012-04-14 10:56
    I've never used it.

    You need to control it with an MCU. Are you doing that?
  • FerienhenriFerienhenri Posts: 6
    edited 2012-04-14 12:48
    thanks leon,

    There is a USB connection and i have a program to read RFID on my computer.

    It's this device: rfid card reader 28340.http://www.parallax.com/Portals/0/Downloads/docs/prod/audiovis/28140-28340-RFID%20Reader-v2.1.pdf

    I'm not sure but i think there is an MCU on rfid reader modules.
  • Mike GreenMike Green Posts: 23,101
    edited 2012-04-14 20:54
    There is a microcontroller on the RFID reader modules. It's an SX (Scenix) which is sold by Parallax, but no longer manufactured. Parallax has a large stock on-hand, enough for years, because it's used in many of their products. If you're interested, there's documentation available here.
  • max72max72 Posts: 1,155
    edited 2012-04-15 07:03
    a little bit off topic, but there is a propeller object for doing RFID using only the prop.
    In the original thread (propeller forum) it was presented the object and shown the waveforms.
  • Mike GreenMike Green Posts: 23,101
    edited 2012-04-15 07:50
    The link to the "World's Simplest RFID Reader" is here. This can also be found in the Propeller Object Exchange as noted in the first post in the thread.
  • FerienhenriFerienhenri Posts: 6
    edited 2012-04-15 08:17
    ok thanks very much but i don't find the pin on the EM4095 to visualize Amplitude modulation ( modulated signal ).

    May be my measure is not correct ( time base, voltage,...)

    do you know this pin ?

    thanks you =)
  • Mike GreenMike Green Posts: 23,101
    edited 2012-04-15 08:26
    Did you try pin #3 as mentioned in post #2?
  • codevipercodeviper Posts: 208
    edited 2012-04-15 08:26
    if you want to see the signal itself that can be achieved. place an inductor between the reader and the card and connect your O-scope to it.
    the Inductor will pick up some signal and generate a low but detectable waveform you can see on your scope.
    just start at the lowest volts per division and go up till it fits well into the vertical range the adjust the time per division till you see the wave.
    I would put this in a metal box so i only see the RFID wave
  • FerienhenriFerienhenri Posts: 6
    edited 2012-04-15 08:56
    =) thanks you everyone

    I have tried to visualize this modulated signal during 3 session. I didn't succeed. I'm not gifted... XD

    To begin, i have tried to visualize a modulated signal on the 12 and 13 pin of the EM4095. No results...

    I have this signals :
    1.png


    I have visualized Clock signal :
    2.png


    and on the number 3 of the EM4095, i have visualized:
    6.png


    What do you think about this signals ?

    Thanks you so much to help me =)
    1.png
    800 x 503 - 37K
    2.png
    800 x 503 - 22K
    6.png
    800 x 503 - 22K
    1.png 37.1K
    2.png 21.7K
    6.png 22.4K
  • FerienhenriFerienhenri Posts: 6
    edited 2012-04-15 09:00
    ok thanks codeviper ! i will try as soon as possible ! =D
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