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Dependencies: mbed
Fork of SineFromPWM by
main.cpp
- Committer:
- wim
- Date:
- 2014-02-18
- Revision:
- 0:d274003b52e7
File content as of revision 0:d274003b52e7:
#include "mbed.h" //Number of dutycycle steps for output wave #define SINE_STEPS 32 //Frequency of output sine in Hz #define SINE_OUT_FREQ 1000 //Constants to compute the sine waveform #define PI 3.141592f #define SINE_STEPS_RAD (2.0f * PI / (float)SINE_STEPS) //Table to generate the sine waveform using dutycycles float sine_duty[SINE_STEPS]; //Frequency of Pulse Width Modulated signal in Hz #define PWM_FREQ 200000 //PWM pin PwmOut PwmPin (p22); //Heartbeat LED DigitalOut myled(LED1); //Ticker to update the PWM dutycycle Ticker pwm_ticker; //Ticker calls this fucntion to update the PWM dutycycle void pwm_duty_updater() { static int idx=0; PwmPin.write(sine_duty[idx]); // Set the dutycycle % to next value in array idx++; // Increment the idx if (idx == SINE_STEPS) idx=0; // Reset the idx when teh end has been reached } int main() { int i; // Init the duty cycle array for (i=0; i<SINE_STEPS; i++) { sine_duty[i] = ( sin(i * SINE_STEPS_RAD) + 1.0f ) / 2.0f; // convert sine (-1.0 .. +1.0) into dutycycle (0.0 .. 1.0) } // Set PWM frequency to 200 KHz (period = 5 us) PwmPin.period( 1.0f / (float) PWM_FREQ); // Init the Ticker to call the dutycyle updater at the required interval // The update should be at (SINE_STEPS * SINE_OUT_FREQ) pwm_ticker.attach(&pwm_duty_updater, 1.0f / (float)(SINE_STEPS * SINE_OUT_FREQ)); while(1){ //infinite loop myled = !myled; wait(0.5); } }