Hello everybody,
I am an eingenering student and I just enter Inside Arduino world!
It is interisting and challenging. I dont have a lot of experience with the direct manipulation of microcontrollers but I programmeted in VHDL fpgq qnd I have knowleged of microeingenering.
I am doing a project regarding telecomunication, optical transmission. I am putting a signal Inside arduino I reqd it I trqnsmitted with a diodo led I receved it with a photodiodo. the signal trasmitted is a PWM. and I want demodulate it or let say I want to extract the sinusoide proportional to the duty cycle in order to obtain the message transmitted.
I really would like to use less possible hardward. I was thinking to obtain a PAM from the PWM in order to find with a RC circuit after the sinusoide but I have no idea how. I need a general help for this beautiful unfoundable ()for the moment) sinusoide!!!
I am using arduino micro, I prescaled the clock 16MHz to 8MHz. my sinusoide that I am transmitting is 50Hz with an amplitude from 0 to 5V.
yes exactly I have read it 1000 time.
I change it a little bit for arduino micro like in the micro there is not timer 2 and I change it in timer 4.
but int he file I have question that are:
I don't have interrupts in arduino micro, I am suppose to subsitute this difference?
Thanks a lot for quick replay 
I am writing bcs I have read all that it is written in the forum italian English and french
The value of a pwm signal is equal to its duty cycle. The digital values of the duty cycle converted to a byte (Ton/T) then have the following correspondance to the phase angle: 0 deg=127, 90 deg=255, 270deg=0 that is asin(dutybyte/127-1). The trouble here is that both division and asin() are very processor intensive operations which cannot be performed in realtime (on an avr arduino at least). If T is fixed and known you can construct a lookup table to give you the phase vaules directly from Ton. The phase will have somme jitter but this can be handled by averaging the phase advance.
No my T it is not fixed... I was thinking that using DDS for a 50Hz frequency it is not the best way. maybe I have to understand how to compare the timer interrupt of the example with the one of arduino micro.. 
Are you sure you can't use an Arduino with an ATmega328p processor like an UNO or Nano or Mini?
I can't, the arduino is not mine and they give me Arduino Micro to do it... I may had found one way to solve this problem, tomorrow I will work on it and I will write here if it is a good solution!
I did ssome modification of http://interface.khm.de/index.php/lab/interfaces-advanced/arduino-dds-sinewave-generator/
for arduino micro.
I am not sure it will work.. Can you see it?
I am using timer 4 instead of timer 2.
demodulo.ino (4.07 KB)
I don't know if you are interested but I change http://interface.khm.de/index.php/lab/interfaces-advanced/arduino-dds-sinewave-generator/ using timer 4 for arduino MICRO qnd it is working
I used the biggest prescaeler. just I need to wait the components for the RC to see if I will have my wonderfull sinusoide!