The basic stages of transmitter are as follows:
USART(serial data) --> FSK modulator-->Led fast switching circuit
The switching circuit is working fine and i have transmitted and received data successfully without modulation.But now i need to add some digital modulation
The issue is that if i send serial data to LED then there is visible blinking of LED but since i need no flickering therefore i have thought of using the modulation stage to remove the blinking but the problem is that whlie desiging FSK modulator there are 2 methods have tried
A) Using 555 IC as shown below, but the circuit is not providing the desired frequency also the circuit becomes complex so does the demodulator, so i have discarded this method
B) USING Softmodem in Arduino.
I have tried using arduino as modulator by following the steps as shown on http://learn.linksprite.com/ardu ... ta-communication-a/ but using this modem ,there is still flickering of LEDs when fed to switching circuit.
There is another way to use XR-2206 ic for desiging FSK modulator but it is not available in my region.
What should be done to use FSK modulation in the circuit. Or suggest some another digital modulation technique (note that the message and carrier signal both needs to be digital).
Thanks in advance.