' DAC Demo Program
' create a waveform in an array and send it to a DAC for sound playback.

wave_length = 31415

dim integer wave(wave_length)
math set 2047, wave()   ' initialize array to mid-voltage

' fill array with a silly waveform
' use a sin wave as the base, shift the frequency around and fade out at the end
for i = 0 to wave_length
 fade = 1
 if i > wave_length * 0.9 then fade = 10 * (wave_length - i) / wave_length
 wave(i) = 2047 + 2000 * fade * sin(i/(4 + sin(i/3141)))
next i

' play the waveform. use interrupt to play only once
done = 0
dac start 10000,wave(),,DAC_INT
done = 0  ' Why this line? Seems to be an immediate interrupt? Mysterious.

do : loop until done   ' wait for sound to end

end

'***************************
sub DAC_INT
 done = 1
end sub