Oscilloscope help

[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

[Darrel Taylor]

FREQOUT makes sine waves and must be filtered, which is not what you need.
Try this ...

PiezoPIN  VAR PORTC.2
TMR0IF    VAR INTCON.2
Width     VAR BYTE
OPTION_REG = %11010011 ; TMR0 1:16

Alarm:
    FOR Width = 161 TO 120 STEP -1
        WHILE !TMR0IF
            TOGGLE PiezoPIN
            PAUSEUS Width
            TOGGLE PiezoPIN
            PAUSEUS Width
        WEND
        TMR0IF = 0
    NEXT Width
GOTO Alarm

[Megahertz]

Thanks Darrel and everyone. It's done

[Megahertz]

Just out of curiosity, can this be achieved without using a microcontroller?