Driving a piezo with the sound function

[Melanie]

I tend to find the Piezo Transducers need a little experimenting to hit it just right... and in typical Melanie fashion I don't use the in-built PBP Commands and tend to roll my own...

Here's what works for me...

	BeepToneHi var Byte		' Variable for Beep High-Period
	BeepToneLo var Byte		' Variable for Beep Low-Period
	BeepLength var Word		' Number of Repitition Cycles to execute


	'
	'	Subroutine Produces Standard Beep for 2 Seconds
	'	-----------------------------------------------
BeepTwoSeconds:
	BeepLength=8800					' For Two Seconds
	Goto BeepRAW
	'
	'	Subroutine Produces Standard Beep for 100mS
	'	-------------------------------------------
BeepShort:
	BeepLength=435					' For 100mS
	Goto BeepRAW
	'
	'	Subroutine Produces Standard Beep for 250mS
	'	-------------------------------------------
Beep:
	BeepLength=1100					' For 250mS
BeepRaw:
	BeepToneHi=111
	BeepToneLo=BeepToneHi-49
	For CounterC=0 to BeepLength
		High Beeper
		PauseUS BeepToneHi
		Low Beeper
		PauseUS BeepToneLo
		Next CounterC
	Return

Let me tell you how sharply the roll-off is for a Piezo... for me BeepTone=111 is just right... 113 or higher gives about 12dB less Sound Output, 109 or lower similarly.

I literally sat there with a Scope and a For-Next Loop giving me a two-second burst of every value from 50 to 200 to finally decide what value was loudest!