FREQOUT command for continuous operation

[richard]

should be easy with a PIC12F1822 @32mhz or reduce the samples to suit,

my idea would be something like this


simple halfwave sin lu table [50 points per cycle]


15,47,77,106,134,160,183,204,221,235,246,252,255,2 54,250,241,229,213,194,172,147,121,92,62,31


set ccp to say 32khz carrier or whatever [make sure 10 bit resolution is viable]

cycle through the table every 400uS
set pulse width(10 bit) to 512+ lu value
next half
cycle through the table every 400uS
set pulse width(10 bit) to 512 - lu value

rinse repeat


for 60 hz cycle every 330 uS


at the o/p filter out carrier

[Aussie Barry]

Thanks Richard.

Your sine lu table appears non-symmetrical. Have you done this for a reason?

Cheers
Barry
VK2XBP

[richard]

its a half wave samples are sin(pi*(I+10)/256 )*256 where I=1 to 25

[Aussie Barry]

Hi All,

I am pleased to advise that I now have a very nice sine wave output from my PIC12F1822.
I dropped the FREQOUT approach and went with the lookup table method instead.

Thanks to all who assisted me with this project.

Cheers
Barry
VK2XBP

[Art]

That totally went over my head So you open and close a PWM signal to produce a sine?
On a scope you see the 50Hz at one scale, and then zoomed, you start to see square edges from the pic? because after all, the output is binary.
Do you then filter the output and get it round?

[Aussie Barry]

Hi Art,

Yes, the PWM output is passed through a second order low pass filter. In my case I used a Sallen-Key LPF.

Cheers
Barry
VK2XBP