Diff: main.cpp

Revision:

0:d274003b52e7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Feb 18 20:08:15 2014 +0000
@@ -0,0 +1,60 @@
+#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);  
+  }
+       
+} 
+