code modification for DRV8312GUI_Main.c

Hi,

/* Convert "Period" (Q15) modulation function to Q0 */\

   Tmp = (int32)v.PeriodMax*(int32)v.MfuncPeriod;  /* Q15 = Q0xQ15 */\

   Period = (int16)(Tmp>>15);                      /* Q15 -> Q0 (Period) */\

"Tmp" is the period value represented as the % of (Q15) the max period whcih is an integer (Q0)

"Period" is Tmp (% of max period in fractional form, Q15) represented as an integer (Q0) which is required for loading into the period register

Please refer to additional information on IQmath.  http://processors.wiki.ti.com/index.php/IQmath_Library_for_C28x

/* Convert "DutyFunc" or "GPR0_BLDC_PWM" (Q15) duty modulation function to Q0 */\

   Tmp = (int32)Period*(int32)GPR0_BLDC_PWM;     /* Q15 = Q0xQ15 */\

EPwm1Regs.CMPA.half.CMPA = (int16)(Tmp>>15); /* PWM signal on output B of EPWM1 (Q15 -> Q0) */\

"Tmp " is the PWM duty cycle as a % of (fraction, Q15) the Period (integer, Q0).  By right-shifting the 32-bit value of TMP by 15 bits, the fractional bits are dropped and are loaded into the 16-bit compare register.  There are additional bits in the compare register that are for HRPWM (high-resolution), the "half" symbol is referencing the lower non-HR bits of the compare registers.  You can find more on this in the PWM chapter of the device user's guide.

Thanks,

Jeff