Posted on March 05, 2016 at 00:26Hello Clive1. Thank you for your help. I tried both of hex files. The first has generated sin wave with amplitude aboute 1.65V and 50hz, but again it wasn't a pure 50hz, it had other frequency components. Comparing with the output seen from my code, your code was generating extra components i think on lower frequency component because the whole wave (50Hz + other) varied slower. For seconde hex I saw upper side of sin (positif cycle) but also the wave was not stable and increasing time axis on osxillocope showed that other components were also present (wavy signal).
I was trying different configurations for my timer to see what changes. The modulated sin wave is 0.5*sin(2*pi ... ). I tried increasing prescaler from 0 to 21-1 (makes 8 mhz timer 1) and period to 400-1 (10khz switching). I saw the expected 50 hz signal but other frequency components were also coming in at frequencies lower than 50Hz. So i conclude that the additional frequency components were different than the one seen with the timer configuration I previously had in my code with no prescaler and period=8400-1 (the code posted in my 1st post). Why is this so?
Another very unusual thing that is happening is that for all timer configurations i mentioned before when i change modulating sin wave from 0.5*sin(2*pi ... ) to 1*sin(2*pi ... ) i am able to get a very clean 50hz with no extra components. How come is this possible? Is there something logical behind this? Thanks for your help.
