I got this code for Space Vector Modulation on github. When I upload it to the Mega anything connected to pin 5 just outputs a constant High as seen in the attached image. I’m using a TimerThree library done by PaulStoffregen. I’m using pins 2 (OC3C), 3 (OC3B), and 5 (OC3A).
#include "FastSin.h"
#include <TimerThree.h>
#define debugPin (8)
//use timer3 for PWM
//T3A pin 5 ; T3B pin 2 ; T3C pin 3
#define phaseA (2) // Original Pin 5
#define phaseB (3) // Original Pin 2
#define phaseC (5) // Original Pin 3
unsigned int degree = 0; // to count degree: 0, 6, 12, 18, ... 354, 0, 6, 12,...
unsigned int SV_angle = 0; //angle of space vector: from [0 to 360)
float SV_magnitude = 0.8f; //magnitude of space vector: from [0 to 1]
//timer3 interupt
void timer3Int(void) //278us
{
//debug pin high when begin interupt
digitalWrite(debugPin, HIGH);
if (degree == 360){
degree = 0;
}
else{
degree += 6;
}
SV_angle = degree;
SVPWM_run(SV_angle, SV_magnitude);
//debug pin low when exit interupt
digitalWrite(debugPin, LOW);
}
void setup()
{
pinMode(debugPin, OUTPUT);
Timer3.initialize(278*5); //timer period us
// we divide 360 degree (1 sin wave cycle (~16,667us) into 60 part)
// 16,667 / 60 ~ 278
// real cycle = 278*60 = 16,680 us (~ 60hz)
// pwm freq : 1/ 278us ~ 3.6kHz
//call these func to setup ports to ouput PWM // These are prettly slow compare to Timer3.setPwmDuty
Timer3.pwm(phaseA, 0);
Timer3.pwm(phaseB, 0);
Timer3.pwm(phaseC, 0);
Timer3.attachInterrupt(timer3Int); // Timer 3 overflow will call timer3Int()
Serial.begin(9600);
}
void loop()
{
}
//this func will calculate and output PWM for 3 switches from angle and magnitude of space vector
void SVPWM_run(unsigned int a, float m)
{
// use "static" to make it a little bit faster. But consume more memory
static float Ualpha, Ubeta;
static float X, Y, Z;
static float PWMa, PWMb, PWMc;
uint8_t sector;
//change from polar to rectangular coordinate
Ualpha = m*icos(a);
Ubeta = m*isin(a);
//X Y Z is temporary variables for convenient
X = Ubeta; //Ubeta
Y = Ubeta*0.5f + Ualpha*0.8660254f; // Ubeta/2 + Ualpha*sqrt(3)/2
Z = Y - X; // -Ubeta/2 + Ualpha*sqrt(3)/2
if (a < 60){
sector = 1;
}
else if (a < 120){
sector = 2;
}
else if (a < 180){
sector = 3;
}
else if (a < 240){
sector = 4;
}
else if (a < 300){
sector = 5;
}
else{
sector = 6;
}
// the calculation below is taken from TI code. I it would take a long time to prove it mathematically.
// So just use the result.. lol.. :)
switch (sector){
case 1: // sector 1 or 4
case 4:
PWMa = Y;
PWMb = X - Z;
PWMc = -Y;
break;
case 2: // sector 2 or 5
case 5:
PWMa = Z + Y;
PWMb = X;
PWMc = -X;
break;
default: // sector 3 or 6
PWMa = Z;
PWMb = -Z;
PWMc = -(X+Y);
break;
}
//after the calculation, PWM is a number from -1 to 1
// we scale it to 0 to 1
PWMa = (PWMa+1)*0.5;
PWMb = (PWMb+1)*0.5;
PWMc = (PWMc+1)*0.5;
//maximum PWM for each pin is 1023. We just need the percentage of 1023
Timer3.setPwmDuty(phaseA, 1023 * PWMa);
Timer3.setPwmDuty(phaseB, 1023 * PWMb);
Timer3.setPwmDuty(phaseC, 1023 * PWMc);
//this is for debugging purposes
//Serial.print("\n");
//Serial.print(a); Serial.print("\t"); Serial.print(sector);
//Serial.print("\n");
//Serial.print(Ualpha, 5); Serial.print("\t");Serial.print(Ubeta, 5);Serial.print("\t");Serial.print(sqrt(Ubeta*Ubeta + Ualpha*Ualpha), 5);
//Serial.print(sector);Serial.print("\t");Serial.print(PWMa, 5); Serial.print("\t"); Serial.print(PWMb, 5); Serial.print("\t"); Serial.print(PWMc, 5);
}
When I switch the pins up two pins output correctly and pin 5 just always outputs a high. I can’t figure out what is wrong, can anyone help me?
