//////////////////////////////////
//
// prog_practice_pwm project
//
// 10/11/22   tj
//
// use ticker and pwm to create a siren
////////////////////////////////
#include "mbed.h"
#include <stdio.h>

#define T_STEP 100000us

////////////////////////
// Global objects/variables for ISRs
PwmOut myPWM(D13);
float siren_per;
uint8_t flag = 0;   // incrementing period (decreasing freq)

void splash(void);
void tkr_isr(void);

int main(void){
    setbuf(stdout, NULL);  // fix output buffer

    // splash
    splash();

    // setup ticker
    Ticker myTK;
    myTK.attach(&tkr_isr, T_STEP);  // note #define must include the us


    // setup PWM parameters
    // close to max volume, mid frequency reange
    myPWM.write(0.9);
    siren_per = 500;  // us

    // hang out
    while(1){
        printf("tick\n");
        wait_us(1000000);   // 1 sec
    }
}

void splash(void){
    printf("\n\nPWM practice program - SIREN\n\n");

    return;
}// end splash

void tkr_isr(void){
    // ticker isr to change period of siren
    // Using flag for direction and using 1KHz - 10KHz
    // in approximatly 18 steps
    if(flag == 0)
        siren_per +=50;
    else 
        siren_per -= 50;

    if(siren_per == 1000)   // 1 KHz
        flag = 1;
    
    if(siren_per == 100)    // 10KHz
        flag = 0;

    // set the PWM period value
    myPWM.period_us(siren_per);

    return;
}// end tkr_isr