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Dependencies:   mbed

main.cpp@0:d76a3b12c090, 2015-08-17 (annotated)

Committer:
VigneshRSR
Date:
Mon Aug 17 00:09:19 2015 +0000
Revision:
0:d76a3b12c090
SawtoothWave

Who changed what in which revision?

UserRevisionLine numberNew contents of line
VigneshRSR 0:d76a3b12c090 1 #include "mbed.h"
VigneshRSR 0:d76a3b12c090 2
VigneshRSR 0:d76a3b12c090 3 //Number of dutycycle steps for output wave
VigneshRSR 0:d76a3b12c090 4 #define SAW_STEPS 33
VigneshRSR 0:d76a3b12c090 5
VigneshRSR 0:d76a3b12c090 6 //Frequency of output sine in Hz
VigneshRSR 0:d76a3b12c090 7 #define SAW_OUT_FREQ 1
VigneshRSR 0:d76a3b12c090 8
VigneshRSR 0:d76a3b12c090 9 //Frequency of Pulse Width Modulated signal in Hz
VigneshRSR 0:d76a3b12c090 10 #define PWM_FREQ 6600
VigneshRSR 0:d76a3b12c090 11
VigneshRSR 0:d76a3b12c090 12 float saw_duty[SAW_STEPS];
VigneshRSR 0:d76a3b12c090 13
VigneshRSR 0:d76a3b12c090 14 //PWM pin
VigneshRSR 0:d76a3b12c090 15 PwmOut mypwm(D10);
VigneshRSR 0:d76a3b12c090 16
VigneshRSR 0:d76a3b12c090 17 //Heartbeat LED
VigneshRSR 0:d76a3b12c090 18 DigitalOut myled(LED1);
VigneshRSR 0:d76a3b12c090 19
VigneshRSR 0:d76a3b12c090 20 //Ticker to update the PWM dutycycle
VigneshRSR 0:d76a3b12c090 21 Ticker pwm_ticker;
VigneshRSR 0:d76a3b12c090 22
VigneshRSR 0:d76a3b12c090 23 //Ticker calls this fucntion to update the PWM dutycycle
VigneshRSR 0:d76a3b12c090 24 void pwm_duty_updater() {
VigneshRSR 0:d76a3b12c090 25 static int idx = 0;
VigneshRSR 0:d76a3b12c090 26 mypwm.write(saw_duty[idx]); // Set the dutycycle % to next value in array
VigneshRSR 0:d76a3b12c090 27 idx++; // Increment the idx
VigneshRSR 0:d76a3b12c090 28 if (idx == SAW_STEPS) idx=0; // Reset the idx when the end has been reached
VigneshRSR 0:d76a3b12c090 29 }
VigneshRSR 0:d76a3b12c090 30
VigneshRSR 0:d76a3b12c090 31 int main() {
VigneshRSR 0:d76a3b12c090 32 float saw[] = {0,
VigneshRSR 0:d76a3b12c090 33 0.03125,
VigneshRSR 0:d76a3b12c090 34 0.0625,
VigneshRSR 0:d76a3b12c090 35 0.09375,
VigneshRSR 0:d76a3b12c090 36 0.125,
VigneshRSR 0:d76a3b12c090 37 0.15625,
VigneshRSR 0:d76a3b12c090 38 0.1875,
VigneshRSR 0:d76a3b12c090 39 0.21875,
VigneshRSR 0:d76a3b12c090 40 0.25,
VigneshRSR 0:d76a3b12c090 41 0.28125,
VigneshRSR 0:d76a3b12c090 42 0.3125,
VigneshRSR 0:d76a3b12c090 43 0.34375,
VigneshRSR 0:d76a3b12c090 44 0.375,
VigneshRSR 0:d76a3b12c090 45 0.40625,
VigneshRSR 0:d76a3b12c090 46 0.4375,
VigneshRSR 0:d76a3b12c090 47 0.46875,
VigneshRSR 0:d76a3b12c090 48 0.5,
VigneshRSR 0:d76a3b12c090 49 0.53125,
VigneshRSR 0:d76a3b12c090 50 0.5625,
VigneshRSR 0:d76a3b12c090 51 0.59375,
VigneshRSR 0:d76a3b12c090 52 0.625,
VigneshRSR 0:d76a3b12c090 53 0.65625,
VigneshRSR 0:d76a3b12c090 54 0.6875,
VigneshRSR 0:d76a3b12c090 55 0.71875,
VigneshRSR 0:d76a3b12c090 56 0.75,
VigneshRSR 0:d76a3b12c090 57 0.78125,
VigneshRSR 0:d76a3b12c090 58 0.8125,
VigneshRSR 0:d76a3b12c090 59 0.84375,
VigneshRSR 0:d76a3b12c090 60 0.875,
VigneshRSR 0:d76a3b12c090 61 0.90625,
VigneshRSR 0:d76a3b12c090 62 0.9375,
VigneshRSR 0:d76a3b12c090 63 0.96875,
VigneshRSR 0:d76a3b12c090 64 1};
VigneshRSR 0:d76a3b12c090 65
VigneshRSR 0:d76a3b12c090 66 for (int i = 0; i < SAW_STEPS; i++) {
VigneshRSR 0:d76a3b12c090 67 saw_duty[i] = saw[i];
VigneshRSR 0:d76a3b12c090 68 }
VigneshRSR 0:d76a3b12c090 69
VigneshRSR 0:d76a3b12c090 70 // Set PWM frequency
VigneshRSR 0:d76a3b12c090 71 mypwm.period( 1.0f / (float) PWM_FREQ);
VigneshRSR 0:d76a3b12c090 72
VigneshRSR 0:d76a3b12c090 73 // Init the Ticker to call the dutycyle updater at the required interval
VigneshRSR 0:d76a3b12c090 74 // The update should be at (SINE_STEPS * SINE_OUT_FREQ)
VigneshRSR 0:d76a3b12c090 75 pwm_ticker.attach(&pwm_duty_updater, 1.0f / (float)(SAW_STEPS * SAW_OUT_FREQ));
VigneshRSR 0:d76a3b12c090 76
VigneshRSR 0:d76a3b12c090 77 while(1){ //infinite loop
VigneshRSR 0:d76a3b12c090 78 myled = !myled;
VigneshRSR 0:d76a3b12c090 79 wait(0.5);
VigneshRSR 0:d76a3b12c090 80 }
VigneshRSR 0:d76a3b12c090 81 }