[PIC] Siren Sound Using Pwm signal

[ajit_nayak87]

I am using PIC16F886 . I am trying to generate fire alarm sound using PWM signal.

Currently i can able to create duty cycle with 2Khz at 50% duty

Now inorder to create siren sound using Timer1 16 bit timer I am trying to create 10ms on time and 10ms OFF time.

PWM signal should be always ON on 10ms Ton time remaining Toff time it should be OFF . can someone suggest how can do it here.

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Code C - [expand]
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#include <htc.h>
#include <stdio.h>
#include<pic.h>
#include<stdint.h>
#define _XTAL_FREQ 20000000
unsigned int i=0; 
#define TMR2PRESCALE 16
long freq;
unsigned int x;
#define LED RC7
#define LED1 RC6
#define LED2 RC2
unsigned short int cnt, num,Dgt=0;
unsigned int i;
unsigned int j;
 
void out_p(int l , int k);
int PWM_Max_Duty()
{
 return(_XTAL_FREQ/(freq*TMR2PRESCALE);
}
PWM1_Init(long fre)
{
 PR2 = (_XTAL_FREQ/(freq*4*TMR2PRESCALE)) - 1;
 freq = fre;
}
 
PWM1_Duty(unsigned int duty)
{
 if(duty<1024)
 { 
 duty = ((float)duty/1023)*PWM_Max_Duty();
 CCP1X = duty & 2;
 CCP1Y = duty & 1;
 CCPR1L = duty>>2;
 }
}
 
PWM1_Start()
{
 CCP1M3 = 1;
 CCP1M2 = 1;
 #if TMR2PRESCALE == 1
 T2CKPS0 = 0;
 T2CKPS1 = 0;
 #elif TMR2PRESCALE == 4
 T2CKPS0 = 1;
 T2CKPS1 = 0;
 #elif TMR2PRESCALE == 16
 T2CKPS0 = 1;
 T2CKPS1 = 1;
 #endif
 TMR2ON = 1;
 TRISC2 = 0;
}
 
PWM1_Stop()
{
 CCP1M3 = 0;
 CCP1M2 = 0;
}
 
 
void SetPWMDutyCycle(unsigned int DutyCycle) // Give a value in between 0 and 1024 for DutyCycle
{
 CCPR1L = DutyCycle>>2; // Put MSB 8 bits in CCPR1L
 CCP1CON &= 0xCF; // Make bit4 and 5 zero
 CCP1CON |= (0x30&(DutyCycle<<4)); // Assign Last 2 LSBs to CCP1CON
}
 
 
void InitPWM(void)
{
 TRISC2 = 0; // Make CCP1 pin as output
 CCP1CON = 0x0C; // Configure CCP1 module in PWM mode
PR2 = 0xFF; // Configure the Timer2 period
 T2CON = 0x01; // Set Prescaler to be 4, hence PWM frequency is set to 4.88KHz.
SetPWMDutyCycle(0); // Intialize the PWM to 0 duty cycle
T2CON |= 0x04; // Enable the Timer2, hence enable the PWM.
}
 
 
void Delay(int k)
{
for(j=0;j<k;j++);
}
void tone(int Frequency,int duration)
{
 SetPWMDutyCycle(Frequency);
 Delay(duration);
 
}
 
 
void Timer1_Interrupt()
 {
 
 INTCON = 0b00000000;
 PIE1=0b00000001;
 PIR1=0x01;
 TMR1H=0x0B;
 TMR1L=0xDC; 
 T1CON=0x31;
 // T1CON=0x01;
 }
 
 
 
 void Init_Controller()
 {
 cnt=100; 
 TRISC=0b00000000; 
 PORTC=0b00000000;
 TRISB=0b10000000;
 PORTB = 0b00000000;
 TRISA=0b00000000; 
 PORTA=0X00; 
 ADCON0 = 0b00000000;
 ANSEL = 0b00000000;
 Timer1_Interrupt();
 LED=0;
 LED1=0;
 LED2=0;
 
 }
 
 
void interrupt isr(void)
 {
 if(TMR1IF==1)
 {
 TMR1H=0xEA; // Load the time value(0x0BDC) for 100ms delay
 TMR1L=0x60; //Timer1 Interrupt for 65000
 TMR1IF=0; // Clear timer interrupt flag
 Dgt++;
 
 LED=!LED;
 LED1=!LED1;
 
 
 } 
 
 }
 
void main(void)
 {
Init_Controller();
 Timer1_Interrupt();
 GIE=1;
 PEIE=1;
 TMR1IE=1;
PWM1_Init(5000);
PWM1_Start();
 
while(1)
 {
 
 PWM1_Duty(500);
 
 }
 
}

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[KlausST]

Hi,

There will be a lot of sirene sound code around...I assume some come with a good description, so you can modify the code for your needs.

I think 2kHz is a bit high.

But what do you mean with 10ms ON and 10ms OFF?...this is 50Hz. I don't think this can be useful for siren sound.

You need to modify the PWM frequency maybe 1kHz continously rising to 2kHz and then back to 1kHz.
There are many different siren sounds..you should decide which one you want...and give some timing of the sweep.

Klaus