volatile int pa, sa[400][3];
HardwareTimer t1(TIM1);

void t1_int(void)
{
 if ((TIM1->SR & 0x0010) == 0x0010)
  {  
   TIM1->SR =0;    // reset int flag - mandatory or else it fires continuously
     
   pa++;   //clock the phase angle counter
   if (pa >= 400)    // done 360 degrees?
     {
       pa = 0;       // then restart at 0 degrees
       GPIOC->ODR = 0x8000;    GPIOC->ODR = 0x0000;    //send a sync pulse for DSO
     }  
   TIM1->CCR1 = sa[pa][0];     // phase 1 pwm width
   TIM1->CCR2 = sa[pa][1];     // phase 2
   TIM1->CCR3 = sa[pa][2];     // phase 3
  }
}


void setup()
{
int i;
float th,p;
// sine() lookup table, with the three phases different by 120 degrees
for (i=0; i < 400; i++)
 {
   th = 2.0 * 3.14159 * (float)i / 400.0;
   p = (1.0 + sin(th)) * 2100;
   sa[i][0] = (int)p;
   th = 2.0 * 3.14159 * (float)(i + 133) / 400.0;    // 399 entries in table = 360 degrees
   p = (1.0 + sin(th)) * 2100;                       // so +133 entries = 120 degrees
   sa[i][1] = (int)p;
   th = 2.0 * 3.14159 * (float)(i + 266) / 400.0;
   p = (1.0 + sin(th)) * 2100;
   sa[i][2] = (int)p;
 }

pa = 0;         // init phase angle = zero

// TIMER1 configs
PWM_pin_config();
Timer1_config();
t1.attachInterrupt(t1_int);
HAL_NVIC_SetPriority(TIM1_UP_TIM10_IRQn ,1,3);
TIM1->DIER = 0x0001;    // let it rip, enable TIMER1

// PC13 LED setup and PC15 for 50Hz sync pulse
pinMode(PC13,OUTPUT);
pinMode(PC15,OUTPUT);
}

void loop()
{
// put the AC voltage control code here
// not a lot to see, we've seen it before
}



void Timer1_config(void)
{
 //
 // timer1, ch1,2,3 OC and OCN outputs enabled with deadtime
 // correct signaling for 3 phase inverter
 //
 uint16_t ccmr1=0, ccmr2=0,  ccer=0;
 __HAL_RCC_TIM1_CLK_ENABLE();
 TIM1->BDTR = 0x0c50;    // DT part is low 8 bits
 TIM1->PSC = 0;
 TIM1->ARR = 4200;
 TIM1->CR1 = 0;
 TIM1->RCR = 0;

 // ch1,2 TIM_OCPreload_Enable & PWM mode 1
 // ch1,2,3 OC and OCN config   OC enabled, active high, OCN enabled, active high
 TIM1->CCER = 0x0555;
 TIM1->CCMR1 = 0x6868;
 TIM1->CCMR2 = 0x0068;

 TIM1->CCR1 = 1;     // ch1 pwm width
 TIM1->CCR2 = 1;     // ch2 pwm width
 TIM1->CCR3 = 1;     // ch3 pwm width
 TIM1->CCR4 = 1;    
 
 TIM1->CR2 = 0;
 TIM1->CR1 |= 0x0080;    // enable preload
 TIM1->BDTR |= 0x8000;   // enable PWM outputs, needed for timer1
 TIM1->CR1 |= 0x0001;    // enable timer
}


void PWM_pin_config(void)
 {
 // manual GPIO setup, the HAL functions do not work with TIMER1 ALT1 complimentary output pins
 // timer 1, ch 1,2,3 alt functions out A8,9,10  
 __HAL_RCC_GPIOA_CLK_ENABLE();
 GPIOA->PUPDR =   0x00154000;    // 10,9,8 pins pull up  01
 GPIOA->OSPEEDR = 0x003fC000;    // speed is 11 or fastest
 GPIOA->MODER =   0x002a8000;    // Alt function
 GPIOA->OTYPER = 0;              // output push-pull
 GPIOA->AFR[1] = 0x00000111;     // AF = 0001 = AF1
 // timer1 ch 1,2,3 complimentary outputs B13,14,15
 __HAL_RCC_GPIOB_CLK_ENABLE();
 GPIOB->PUPDR =   0x54000000;
 GPIOB->OSPEEDR = 0xfc000000;
 GPIOB->MODER =   0xa8000000;
 GPIOB->OTYPER = 0;
 GPIOB->AFR[1] =  0x11100000;
 }