FSK modulator / Demodulator using PIC microcontroller

Thread Starter


Joined Aug 20, 2009
Hello all!

First sorry for my english.

I am not really sure that what I want to make is a FSK modulator. In this picture you can see a PIC16F84A uController and a resistor ladder. I wrote an asm code for pic ucontroller, and, depending on wich one of the 3 switches is on or off, I see on the virtual osciloscope a sine signal. For example if switch 1 and switch 3 are on (like in the picture above), the sine signal will be composed from 2 parts of high freq and one with low freq, something like this.
Here you can find the .asm and hex code for pic16f84a. I really need some help:

1. Could someone who is good in pic uControllers programming help me to improove my code because I have some problems with timing? In this picture you can see that the lenghts are not equal.
2. After improoving my code , I want to transmit this sine signal trough radio waves to a demodulator circuit. After the signal will be demodulated, a pic16f84 will receive a 3 bits code (for example 101, 001, 110 etc.) and a led will light to the correspond code . But I don't know how to build neither the microtransmmiter or the demodulator circuit (I want to transmit the signal to a small distance, about 100m).

Please someone help me but with good instructions and schematics. I really don't want to be desoriented.

Sorry again for my bad english and I hope you understood me. I am from Romania and I am 17. Thanks:).