I want to control the volume of the output using Sound command.

[HenrikOlsson]

Hi,
First of all, the manual states that the duration part of the sound statement should be 0-255, you're specifying 65535.
Second, and what I think is the main "mistake", is in your interpretation of how ON INTERRUPT works.

ON INTERRUPT isn't a real hardware interrupt. It will only check the interrupt flag between each PBP statement. If you specify a sound duration of 255 the sound command takes 255*12ms=3060ms so the ISR will only execute once ever ~3 seconds even if TMR0 overflows once every 65ms. Had it worked with 65535 as the duration the ISR would only execute every 786th second.

Finally, doing things like IF X>255 THEN when X is declared as a BYTE doesn't do anything because X can never be larger than 255 anyway. You can safely keep adding 5 to it, it will wrap around by itself.

Hope it helps.

/Henrik.

[billys7]

Yes you are right.
How can i make a real interrupt ?

[mackrackit]

You can use
http://darreltaylor.com/DT_INTS-14/intro.html
This is the easy way.

Or you can read in the manual for an explanation on how to write your own.

[HenrikOlsson]

I don't see the need for an interrupt for what you're doing there.

X = 5
Start:
   HPWM 3, X, 20000
   SOUND PortC.3, [255, 5]   ' Make sound for ~60ms
   X = X + 5
Goto Start

Though I'd probably setup the CCP module manually and write to the dutycycle register instead of using the HPWM command since I Believe you'll get some discontinuties in the output when constantly changing the dutycycle using HPWM - may be wrong on that and/or it may not matter in your case, try it.

/Henrik.

[billys7]

Totaly, i have tried all the methods you have suggested me, unfortunately the results wasn't so good.
In every case, there was a small interrupt on the sound.

I decided to produce the white noise by an external small circuit, and then to process it with PWM.

Thank you all.