UnderWater Antenna 125KHz Driver using a 16F628 @20MHz Example Code


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  1. #1
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    Default UnderWater Antenna 125KHz Driver using a 16F628 @20MHz Example Code

    Hello,

    I am looking for a PBP 3.1 example of how to implement hardware PWM @125KHz using a 16F628.
    Attached below is a link to the Microchip App note showing the schematic that I intended to build.
    I have an old development board from Bruc Reynolds which is all set up with a 20MHz Xtal.

    From the data sheet...(Linked Below)

    For a device operating at20 MHz, one can obtain a 125 kHz signal by setting theTimer2 prescaler to 1.
    A period of 8 μs is then obtainedby setting the PR2 register to 39.
    To get a 50% dutycycle output, set CCPR1L to 14 and CCP1CON<5:4>to <0:0>.
    These settings will ensure a constant carrier.
    To modulate the data, one can turn the drive signal onand off by setting and clearing the CCP1RIL bit.

    FYI, this is for an underwater antenna that I am experimenting with.

    Thanks,

    Jay Zebryk, W1JRZ

    https://ww1.microchip.com/downloads/...tes/00232B.pdf

  2. #2
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    Default Re: UnderWater Antenna 125KHz Driver using a 16F628 @20MHz Example Code

    This might make things easier:-)

    Name:  Microchip Base Station Schematic.png
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  3. #3
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    Default Re: UnderWater Antenna 125KHz Driver using a 16F628 @20MHz Example Code

    Hi Jay.

    I am not sure what RB3, RB4 and RB7 are used for. I guess the RB3 is the PWM signal output, but the rest?

    As I understand it, you just want a 50% square signal at 125KHz?

    Ioannis

  4. #4
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    Default Re: UnderWater Antenna 125KHz Driver using a 16F628 @20MHz Example Code

    Ioannis,

    I have the beast generating 125KHz from the hardware module quite nicely.
    To modulate a data stream, I am simply changing
    TRISB.3 from an Output to an Input.

    Peace,

    Jay Zebryk


  5. #5
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    Default Re: UnderWater Antenna 125KHz Driver using a 16F628 @20MHz Example Code

    So, you are generating the 125KHz 50% duty cycle signal?

    Ioannis

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