PWM (ECCP) - piezo-sounder directly connected to half-bridge on PIC

[flotulopex]

That's the code, well... it's just THE part of the cooking-timer code to make that "half-bridge" PWM work:

'-------------------------------------------------------------------------------
' PIC 16F690 Fuses (MPASM)
@ __config _FCMEN_OFF &_IESO_OFF &_CPD_OFF &_WDT_OFF &_HS_OSC &_BOR_OFF &_CP_OFF &_PWRTE_OFF &_MCLRE_OFF

'-------------------------------------------------------------------------------
' Registers   76543210
OPTION_REG = %10000110 ' Pull-Ups OFF, Prescaler TMR0 1:128
ANSEL      = %00000000 ' Select analog inputs Channels 0 to 7
ANSELH     = %00000001 ' Select analog inputs Channels 8 to 11
WPUA       = %00000000 ' Select weak pull-ups
WPUB       = %00000000 ' Select weak pull-ups
ADCON0     = %10000000 ' AD Module
ADCON1     = %00000000 ' AD control register
CM1CON0    = %00000000 ' Comparator1 Module
CM2CON0    = %00000000 ' Comparator2 Module
INTCON     = %10100000 ' INTerrupts CONtrol; GIE=1, T0IE=1
TRISA      = %00000000 ' Select Input/Output (0 to 5)
PORTA      = %00000000 ' Set High/Low (0 to 5)
TRISB      = %00110000 ' Select Input/Output (4 to 7)
PORTB      = %00000000 ' Set High/Low (4 to 7)
TRISC      = %01000000 ' Select Input/Output (0 to 7)
PORTC      = %00000000 ' Set High/Low (0 to 7)

' HPWM registers
T2CON      = %00000101 ' Timer2 = ON (bit2), prescaler (bits1:0) 00=1, 01=4, 1x=16
CCP1CON    = %10001100 ' Select PWM Mode (%00001100 = PWM module ON)
CCPR1L     = 62        ' Dutycycle set to 50% (= percentage of PR2)
PR2        = 124       ' Freq 4kHz

[Ioannis]

Just as a precaution I would recommend to have the outputs at the same logic level when you do not want the sounder work. Thats because piezo do not like DC voltage.

Ioannis

[fratello]

Thanks Mr.Flotulopex and Mr.Ioannis !
It's verry usefull.

[flotulopex]

...I would recommend to have the outputs at the same logic level...

When the souder is not used, I set CCP1CON register to 0.

Is this okay?

[flotulopex]

....hum, sorry for my silly question

Just measured the ports and they need to be reset.

Thanks for noticing Ioannis

[Ioannis]

As you observed Roger, you must be in luck to have both ports at the same level. They will be in a random state.

Ioannis