Using external isolated ADC

Hello, i am using Instaspin MCU TMS320F28027F and want to use small MCU to sample voltages and currents on a hot side, i have an idea how to make it, but i want someone more experienced to check it.  PWM will generate interrupt instead of SOC, in interrupt i notify ADC to start conversion by setting GPIO pin high, waiting 2uS (to complete conversion) and then start receiving 16 bytes by SPI, but i dont know how to implement it better, because DMA doesnt work with SPI and SPI FIFO is only 4 half-words deep. I have an idea to receive each byte in interrupt until we receive all 16, and then run FOC.

Here is what i changed. Changes in main()

HAL_enableAdcInts(halHandle);
to
HAL_enablePwmInt(halHandle);

In HAL_setupPwms()

PWM_disableInt(obj->pwmHandle[PWM_Number_1]);
PWM_setSocAPulseSrc(obj->pwmHandle[PWM_Number_1],PWM_SocPulseSrc_CounterEqualZero);
PWM_enableSocAPulse(obj->pwmHandle[PWM_Number_1]);
to
PWM_disableSocAPulse(obj->pwmHandle[PWM_Number_1]);
PWM_enableInt(obj->pwmHandle[PWM_Number_1]);
PWM_setIntMode(obj->pwmHandle[PWM_Number_1], PWM_IntMode_CounterEqualZero);

Changed HAL_SetTrigger() 

static inline void HAL_setTrigger(HAL_Handle handle,const SVGENCURRENT_IgnoreShunt_e ignoreShunt,const int16_t minwidth, const int16_t cmpOffset)
{
  HAL_Obj *obj = (HAL_Obj *)handle;

  PWM_Obj *pwm1 = (PWM_Obj *)obj->pwmHandle[PWM_Number_1];
  PWM_Obj *pwm2 = (PWM_Obj *)obj->pwmHandle[PWM_Number_2];
  PWM_Obj *pwm3 = (PWM_Obj *)obj->pwmHandle[PWM_Number_3];
  PWM_Obj *pwm;

  uint16_t nextPulse1 = (pwm1->CMPA + pwm1->CMPAM) / 2;
  uint16_t nextPulse2 = (pwm2->CMPA + pwm2->CMPAM) / 2;
  uint16_t nextPulse3 = (pwm3->CMPA + pwm3->CMPAM) / 2;
  uint16_t pwmCMPA1 = pwm1->CMPA;
  uint16_t pwmCMPA2 = pwm2->CMPA;
  uint16_t pwmCMPA3 = pwm3->CMPA;

  int16_t offset;

  if(ignoreShunt == use_all)
    {
      if((nextPulse1 <= nextPulse2) && (nextPulse1 <= nextPulse3))
        {
          pwm = pwm1;
        }
      else if((nextPulse2 <= nextPulse1) && (nextPulse2 <= nextPulse3))
        {
          pwm = pwm2;
        }
      else
        {
          pwm = pwm3;
        }
    }
  else if(ignoreShunt == ignore_a)
    {
      offset = pwmCMPA1 + cmpOffset;
    }
  else if(ignoreShunt == ignore_b)
    {
      offset = pwmCMPA2 + cmpOffset;
    }
  else if(ignoreShunt == ignore_c)
    {
      offset = pwmCMPA3 + cmpOffset;
    }
  else if(ignoreShunt == ignore_ab)
    {
      if(pwmCMPA1 > pwmCMPA2)
        {
          offset = pwmCMPA1 + cmpOffset;
        }
      else
        {
          offset = pwmCMPA2 + cmpOffset;
        }
    }
  else if(ignoreShunt == ignore_ac)
    {
      if(pwmCMPA1 > pwmCMPA3)
        {
          offset = pwmCMPA1 + cmpOffset;
        }
      else
        {
          offset = pwmCMPA3 + cmpOffset;
        }
    }
  else // when ignoreShunt == ignore_bc
    {
      if(pwmCMPA2 > pwmCMPA3)
        {
          offset = pwmCMPA2 + cmpOffset;
        }
      else
        {
          offset = pwmCMPA3 + cmpOffset;
        }
    }


  if(ignoreShunt == use_all)
    {
      if(pwm->CMPAM >= (pwm->CMPA + pwm->DBFED))
        {
          pwm1->CMPB = (pwm->CMPAM - (pwm->CMPA + pwm->DBFED)) / 2 + 1;
          //PWM_setSocAPulseSrc(obj->pwmHandle[PWM_Number_1],PWM_SocPulseSrc_CounterEqualCmpBDecr);
          PWM_setIntMode(obj->pwmHandle[PWM_Number_1], PWM_IntMode_CounterEqualCmpBDecr);
        }
      else
        {
          pwm1->CMPB = ((pwm->CMPA + pwm->DBFED) - pwm->CMPAM ) / 2 + 1;
          //PWM_setSocAPulseSrc(obj->pwmHandle[PWM_Number_1],PWM_SocPulseSrc_CounterEqualCmpBIncr);
          PWM_setIntMode(obj->pwmHandle[PWM_Number_1], PWM_IntMode_CounterEqualCmpBIncr);
        }
    }
  else
    {
      pwm1->CMPB = offset;
      //PWM_setSocAPulseSrc(obj->pwmHandle[PWM_Number_1],PWM_SocPulseSrc_CounterEqualCmpBIncr);
      PWM_setIntMode(obj->pwmHandle[PWM_Number_1], PWM_IntMode_CounterEqualCmpBIncr);
    }

  return;
}

Added PWM interrupt vector

static inline void HAL_initIntVectorTable(HAL_Handle handle)
 {
  HAL_Obj *obj = (HAL_Obj *)handle;
  PIE_Obj *pie = (PIE_Obj *)obj->pieHandle;


  ENABLE_PROTECTED_REGISTER_WRITE_MODE;

  //pie->ADCINT1 = &mainISR; // Dont know yet what will trigger mainISR
  pie->EPWM1_INT = &startConvISR;

  DISABLE_PROTECTED_REGISTER_WRITE_MODE;

  return;
 }

Also created ISR for PWM int

interrupt void startConvISR(void)
{
  HAL_acqPwmInt(halHandle, PWM_Number_1);
  // Notify external ADC
  return;
}