Arduino as an FSK Modem - SEO, SEM, Web, eCommerce, iOS, Cloud, HTML5, Chrome Apps and Android

18 responses

  1. Amer
    September 22, 2010

    Hello Shajir,
    I am interesting in build a modem for telemetry of my RC airplane. Can you give me more information from softModem library.

    Thank you in avance.

  2. Shajir
    September 23, 2010

    Hi Amer,
    You can download the softModem library and sample codes from

  3. yut
    October 10, 2010

    how can change AFSK(square wave to sine wave), because softModem generate square wave

  4. Shajir
    October 11, 2010

    I think, modulate FSK with a carrier signal by AM or FM technique get a RF signal corresponding to the FSK and we can transmit it using wireless transmission and demodulate at the terminal point using appropriate demodulation technique.

  5. yut
    October 15, 2010

    out put from softmodem (ARDUINO) is square wave.I think it can not FM modulate technique

  6. Shajir
    October 15, 2010

    we only note the frequency change at the terminal point for decoding the data. so don’t worry about the distortion.

  7. yut
    October 19, 2010

    Can you send and receive number (0 2 3 4 5 6 7 8 9) by sofmodem.
    I have try it ,but it can only send-receive TEXT

  8. yut
    October 19, 2010

    Can you send and receive NUMBER(0 1 2 3 4 5 6 7 8 9) by softmodem.I have try it ,but it can only send-receive TEXT.

  9. yut
    October 19, 2010

    can you send and receive NUMBER(0123456789)by softmodem.I have try it, but it can only send – receive TEXT.

  10. Shajir
    October 19, 2010

    Every character is send as its ASCII value. For 0 it send and receive its ASCII 48. So for getting a number we have to subtract 48 from the receive character.

  11. yut
    October 19, 2010

    please send me for complete code.
    And how can I change FSK frequency ,I have change code in SoftModem.h to the following
    #define SOFT_MODEM_BAUD_RATE (126)
    #define SOFT_MODEM_LOW_FREQ (882)
    #define SOFT_MODEM_HIGH_FREQ (1764)
    #define SOFT_MODEM_MAX_RX_BUFF (4)

    but it can’t decode

    Because,low frequency can send through VHF transceiver.

    Thank you

  12. Shajir
    October 19, 2010

    complete code in softmodem lib. you can edit and change the frequency according to your requirements.

  13. david
    March 24, 2011

    I noticed you mentioned a filter on the 2 pins but I only see one?

  14. shajir
    March 24, 2011

    There are two filters ,one in digital pin 3 (for output) and the other in digital pin 6 (for input).

  15. Don
    March 25, 2013

    can you tell me whitch libary’s are you used in your code example?

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