Control volume out of chip with pwm

stilgar

In my project I have a LED that fades on. I would like to have sound to fade on with the LED. I am using wave player.
I use PWM to fade on the LED, could this be used to control volume? The amp used for the sound has no volume control to it, so I would need another way to do it.

http://www.jbhifi.com.au/images/gumball-3000-portable-speakers-sku-69414-large.gif

I first thought was to use a transistor connected to a extra pin and send the same PWM signal to it as the LED.
Is there a way to do this without adding hardware??

Thanks

Phil Pilgrim (PhiPi)

You can control the volume form this statement in the player routine. Change:

      frqa := byte[addr++] << 24                                ' update dac

to read:

      frqa := ((byte[addr++] - $80) * volume) << 16 + $8000_0000

where volume is a volume level that ranges between 0 (muted) and 255 (full) and can be ramped up and down from your main program. The catch is that it adds some overhead to the playback, which will limit the rate. Hopefully, the rate you're currently using can stand the extra overhead.

-Phil

stilgar

Phil Pilgrim (PhiPi) wrote: »

You can control the volume form this statement in the player routine. Change:

      frqa := byte[addr++] << 24                                ' update dac

to read:

      frqa := ((byte[addr++] - $80) * volume) << 16 + $8000_0000

where volume is a volume level that ranges between 0 (muted) and 255 (full) and can be ramped up and down from your main program. The catch is that it adds some overhead to the playback, which will limit the rate. Hopefully, the rate you're currently using can stand the extra overhead.

-Phil

Ok, this may seem a dumb question. After I change the line in the player, in my main program I add the VAR as volume? then set it as " volume = 127 " near the fade on LED section?? or did I do this wrong again (still learning about variables)

stilgar

I got the sound to go up, now the qestion is how to make it stop at 64 (same as maxbrite?

my code:
wavcog := cognew(playsound(10, @Cylon, 0), @stack) + 1 ' start sound player

repeat luminosity from 0 to maxbright
volume := (volume + 1) 'ranp volume up need to stop at 64 (maxbright)

repeat x from 7 to _numleds-9
leds[x] := luminosity + 1
waitcnt(clkfreq / (rtime1 / 1000)+ cnt) ' center LEDs slowly go from 0 to maxbright = 64

Phil Pilgrim (PhiPi)

how to make it stop at 64

volume := ++volume <# 64

-Phil

stilgar

Phil Pilgrim (PhiPi) wrote: »

volume := ++volume <# 64

-Phil

Thanks a bunch, I under stand " ++ " means ramp up, but I don't remember seeing " <# " before. does that mean, " less than number "?

Phil Pilgrim (PhiPi)

stilgar wrote:

I don't remember seeing " <# " before. does that mean, " less than number "?

It's the MAX operator. You can think of it as meaning "but not more than."

-Phil

stilgar

thanks, I will have to look into that a bit more