Oscilloscope help

[kellyseye]

Looks like 'swept' signal.

The square wave frequency is being increased (swept) from x(Hz) to y(Hz) by a modulating waveform. It 'looks' like it's sweeping from around 2kHz to 3kHz by a low (250Hz???) signal.

Configure an output to a 2kHz square wave and arrange for it to increase by 4Hz every 4uS until it reaches 3kHz then repeat.

[Megahertz]

Hello kellyseye, I tried the following, but no sucess:

while 1
		Pulsout PortC.0,25
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,24
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,23 
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,22
@	NOP
@	NOP
@	NOP
@	NOP		
		Pulsout PortC.0,20 
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,19
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,18 
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,17
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,16 
@	NOP
@	NOP
@	NOP
@	NOP
		Pulsout PortC.0,15
@	NOP
@	NOP
@	NOP
@	NOP

Wend

[Megahertz]

Here I have recorded the sound produced by the buzzer. Please rename the attachment to "Memo.m4a" from ".pdf" as I could not upload it in its original format.

[Darrel Taylor]

Try this ...
You'll need to put the piezo circuit on a CCP pin.

Freq  VAR WORD

Main:
    FOR Freq = 3000 TO 4000 STEP 10    
        HPWM 1, 127, Freq
        PAUSE 1 
    NEXT Freq
GOTO Main

It should sound something like this ... http://support.melabs.com/DT/Piezo.wma

[Megahertz]

Thanks Darrel, I will try it tomorrow with 16f877A which I have. But I would like to ask if this task can be made possible using a smaller PIC without an HPWM, I would like to use 16F676 if possible as it is very easily available and where I am and if this takes off then it will be economical as well.

In the mean time I am attaching the datasheet of the Chinese uC which is controlling the base of the NPN transistor connected to the piezo & coil. The signal comes out from PIN 2, which to me seems just an I/O pin.

Thanks

[Darrel Taylor]

Yes, of course it can.
It's only 3-4 khz. You can generate that in software easily.

But see if it drives your piezo first.
I was assumming your piezo has a resonant frequency of ~3.5khz.

[Megahertz]

THANKS Darrel, it worked like a charm with HPWM. Any pointers as to how to do without it.

I tried FREQOUT

    FOR Freq = 3000 TO 4000 STEP 10    
        FREQOUT PortC.2,1, Freq
    NEXT Freq

but the results were not the same, not even near enough, the pulsing sound is not that prominent