notch_60.c

pic16c6x和pic16c7xxx都可以通用

/*****************************************************************************
* 60 Hertz Notch Filter
*
* Written for "Digital Signal Processing with the PIC16C74" Application Note.
*
* This example program use the filter() function to implement a 60Hz notch
* filter. T0 is used to generate a 1kHz sample clock. The program samples the 
* input signal x(n) on A-D channel 1, calls the filter routine  signal, and 
* outputs y(n) to PWM channel 1.
*
* If FILTER set to 0, performs straight talkthru from A-D to PWM output. 
* T0 period can be changed to cary the sample rate. 
*
* D. Mostowfi 4/95
******************************************************************************/
#include <16c74.h>         /* c74 header file */

#include "analogio.c"      /* analog I/O module */
#include "iir_filt.c"      /* iir filter module */

#define FILTER          1

/* Function Prototypes */
void main_isr();
void timer0_isr();


/*****************************************************************************
* main isr - 16C74 vectors to 0004h (MPC __INT() function) on any interrupt *
* assembly language routine saves W and Status registers then tests flags in
* INTCON to determine source of interrupt. Routine then calls appropriate isr.
* Restores W and status registers when done.
*****************************************************************************/
void __INT(void)
{

    if(INTCON.T0IF){            /* timer 0 interrupt ? */
      INTCON.T0IF=0;            /* clear interrupt flag */
      timer0_isr();             /* and call timer 0 isr */
    }

/* Restore W, WImage, and STATUS registers */

#asm                            
        BCF     STATUS,RP0      ;Bank 0
        MOVF    temp_PCLATH, W
        MOVWF   PCLATH          ;PCLATH restored
        MOVF    temp_WImage, W
        MOVWF   __WImage        ;__WImage restored
        MOVF    temp_FSR, W
        MOVWF   FSR             ;FSR restored
        SWAPF   temp_STATUS,W
        MOVWF   STATUS          ;RP0 restored
        SWAPF   temp_WREG,F
        SWAPF   temp_WREG,W     ;W restored
#endasm

}

/*****************************************************************************
* timer 0 interrupt service routine
***************************************************************************/
void timer0_isr(void)
{
    TMR0=100;                   /* reload value for 1ms period */
    PORTB.0=!PORTB.0;           /* toggle PORTB.0 */
    sample_flag=active;         /* set sample flag */
}


void main()
{

/* initialize OPTION register */
    OPTION=0b00000011;          /* assign prescaler to T0 */

/* initialize INTCON register (keep GIE inactive!) */
    INTCON=0b00000000;          /* disable all interrupts */

/* initialize PIE1 and PIE2 registers (periphreal interrupts) */
    PIE1=0b00000000;            /* disable all peripheral interrupts */
    PIE2=0b00000000;

/* initialize T1CON and T2CON registers */
    T1CON=0b00000000;           /* T1 not used  */
    T2CON=0b00000000;           /* T2 not used  */

/* initialize CCPxCON registers */
    CCP1CON=0b00001100;         /* set CCP1CON for PWM mode */
    CCP2CON=0b00000000;         /* CCP2CON=0 (PWM 2 not used) */

/* initialize SSPCON register */
    SSPCON=0b00000000;          /* serial port - not used */

/* initialize ADCONx registers */
    ADCON0=0b00000000;          /* a-d converter */
    ADCON1=0b00000010;          

/* initialize TRISx register (port pins as inputs or outputs) */
    TRISA=0b00001111;
    TRISB=0b00000000;
    TRISC=0b11111011;
    TRISD=0b11111111;
    TRISE=0b11111111;

/* clear watchdog timer (not used) */
    CLRWDT();

/* initialize program bit variables */
   FLAGS=0b00000000;

/* intialize output port pins */
   PORTB=0;

/* enable interrupts...  */

    INTCON.T0IE=1;              /* peripheral interrupt enable */
    INTCON.GIE=1;               /* global interrupt enable */

    init_PWM(0x40);             /* init PWM port */
    init_filter();              /* init filter */
    while(1){
      while(!sample_flag){}     /* wait for sample clock flag to be set */
        sample_flag=0;          /* clear sample clock flag */
        x_n=get_sample(1);      /* read ADC channel 1 into x(n) */
        if(FILTER==1){          /* if filter enabled */
          filter();             /* call filter routine */
        }
        else{                   /* or else write x(n) to y(n) (talkthru) */
          y_n=x_n;
        }
        write_PWM((char)y_n,0); /* write y_n to PWM port 1 */
    }
}