Wayne McLachlan / Mbed 2 deprecated sine3-v2

Uses trigonometry to produce high quality 3 phase sinewave output waveworms on the PWM. Tested from 30 to 100Hz at 10kHz modulation. Changes frequency glitch free. Amplitude is scalable. Could be used as a basic invertor back-end. Not optimised for processor overhead, could be modified to use lookup tables if less accuracy required. Oscilloscope trace here: http://mbed.org/users/waynemcl/notebook/sine3-v2/

Dependencies:   mbed

main.cpp@0:d040778370fc, 2010-11-28 (annotated)

Committer:
waynemcl
Date:
Sun Nov 28 22:39:32 2010 +0000
Revision:
0:d040778370fc
v2

Who changed what in which revision?

UserRevisionLine numberNew contents of line
waynemcl 0:d040778370fc 1 #include "mbed.h"
waynemcl 0:d040778370fc 2 #include "stdio.h"
waynemcl 0:d040778370fc 3
waynemcl 0:d040778370fc 4 #define PI 3.1416
waynemcl 0:d040778370fc 5
waynemcl 0:d040778370fc 6 // License: You may copy or modify and re-use this code, but you MUST credit me:
waynemcl 0:d040778370fc 7 // Wayne McLachlan, www.embeddedengineering.co.nz
waynemcl 0:d040778370fc 8 // You may add your name to the author list if you have done significant modifications or improvements
waynemcl 0:d040778370fc 9
waynemcl 0:d040778370fc 10 PwmOut chA(p21);
waynemcl 0:d040778370fc 11 PwmOut chB(p22);
waynemcl 0:d040778370fc 12 PwmOut chC(p23);
waynemcl 0:d040778370fc 13
waynemcl 0:d040778370fc 14 Serial pc(USBTX, USBRX);
waynemcl 0:d040778370fc 15 Ticker sine3ticker;
waynemcl 0:d040778370fc 16
waynemcl 0:d040778370fc 17 #define SINE3_PWM_FREQ 10000
waynemcl 0:d040778370fc 18
waynemcl 0:d040778370fc 19 unsigned char sine3freq;
waynemcl 0:d040778370fc 20 float sine3mag;
waynemcl 0:d040778370fc 21 float sine3theta;
waynemcl 0:d040778370fc 22
waynemcl 0:d040778370fc 23 void sine3tick() {
waynemcl 0:d040778370fc 24 // offset PWM for bipolar: 0.5 => 0V
waynemcl 0:d040778370fc 25 chA = 0.5 + (sine3mag * sinf(sine3theta) /2);
waynemcl 0:d040778370fc 26 chB = 0.5 + (sine3mag * sinf(sine3theta + 2*PI /3)/2); // + 120 degrees
waynemcl 0:d040778370fc 27 chC = 0.5 + (sine3mag * sinf(sine3theta + 2*PI*2/3)/2); // + 240 degrees => - 120 degrees
waynemcl 0:d040778370fc 28
waynemcl 0:d040778370fc 29 sine3theta += 2*PI / (SINE3_PWM_FREQ / sine3freq); // one cycle / steps per cycle
waynemcl 0:d040778370fc 30 if (sine3theta >= 2*PI) {
waynemcl 0:d040778370fc 31 sine3theta = 0;
waynemcl 0:d040778370fc 32 }
waynemcl 0:d040778370fc 33 }
waynemcl 0:d040778370fc 34
waynemcl 0:d040778370fc 35
waynemcl 0:d040778370fc 36 void sine3_init() {
waynemcl 0:d040778370fc 37 chA.period_us( 1000000 / SINE3_PWM_FREQ ); // period in uS. Common to all PWM
waynemcl 0:d040778370fc 38 chA = 0.5;
waynemcl 0:d040778370fc 39 chB = 0.5;
waynemcl 0:d040778370fc 40 chC = 0.5;
waynemcl 0:d040778370fc 41
waynemcl 0:d040778370fc 42 sine3mag = 0.9; // prevent overmodulation
waynemcl 0:d040778370fc 43 sine3freq = 55; // compromise between 50Hz and 60Hz
waynemcl 0:d040778370fc 44 sine3theta = 0;
waynemcl 0:d040778370fc 45 sine3ticker.attach_us(&sine3tick, (1000000 / SINE3_PWM_FREQ) ); // period in uS
waynemcl 0:d040778370fc 46 //pc.printf("\n\r init ");
waynemcl 0:d040778370fc 47 }
waynemcl 0:d040778370fc 48
waynemcl 0:d040778370fc 49
waynemcl 0:d040778370fc 50 int main() {
waynemcl 0:d040778370fc 51 sine3_init();
waynemcl 0:d040778370fc 52 while (1) {
waynemcl 0:d040778370fc 53 sine3freq++;
waynemcl 0:d040778370fc 54 if (sine3freq > 100) {
waynemcl 0:d040778370fc 55 sine3freq = 30;
waynemcl 0:d040778370fc 56 pc.printf("\n\r");
waynemcl 0:d040778370fc 57 }
waynemcl 0:d040778370fc 58 wait(0.2);
waynemcl 0:d040778370fc 59 pc.printf("%d ",sine3freq);
waynemcl 0:d040778370fc 60 }
waynemcl 0:d040778370fc 61 }