stm32f3 discovery how to fix loop periode !!

Posted on October 26, 2016 at 02:14

So use a free running 32-bit TIM at a granularity you want to either a) time stamp the measurement epochs, or b) manage the loop iterations.

You could also use the DWT_CYCCNT to get into the sub-microsecond realm for loop iterations. Covered this here multiple times, review other posts

//******************************************************************************
// sourcer32@gmail.com
volatile unsigned int *DWT_CYCCNT = (volatile unsigned int *)0xE0001004; //address of the register
volatile unsigned int *DWT_CONTROL = (volatile unsigned int *)0xE0001000; //address of the register
volatile unsigned int *SCB_DEMCR = (volatile unsigned int *)0xE000EDFC; //address of the register
//******************************************************************************
void EnableTiming(void)
{
static int enabled = 0;
if (!enabled)
{
RCC_ClocksTypeDef RCC_Clocks;
RCC_GetClocksFreq(&RCC_Clocks);
*SCB_DEMCR |= 0x01000000;
*DWT_CYCCNT = 0; // reset the counter
*DWT_CONTROL |= 1 ; // enable the counter
enabled = 1;
}
}
//******************************************************************************
void TimingDelay(unsigned int tick)
{
unsigned int start, current;
start = *DWT_CYCCNT;
do
{
current = *DWT_CYCCNT;
} while((current - start) < tick);
}
//******************************************************************************
TimingDelay(SystemCoreClock); // One Second of ticks
TimingDelay(SystemCoreClock / 1000000); // One Microsecond of ticks

Posted on October 26, 2016 at 18:45

thank you so much for your answer , i think it will help me a lot ;)

this is my code and what i  want to do i written inside the code ( the main function )

 

int main(void)

{  

  /* SysTick end of count event each 10ms */

  RCC_GetClocksFreq(&RCC_Clocks);

  SysTick_Config(RCC_Clocks.HCLK_Frequency / 100);

 

  /* Configure the USB */

     Demo_USB();

  /* Configure the gyroscope */  

     Demo_GyroConfig();

  /* Configure the accelerometer */

     Demo_CompassConfig();

  /* Infinite loop */

  while (1)

  {

           *********At the start of each loop, I get the current time*******************

                 exemple --->        ---- current_time() = start_time ----

                   

                   

    //read ACC and GYR data

    Demo_CompassReadAcc(acc_raw);

    Demo_GyroReadAngRate(gyr_raw);

    //Convert Gyro raw to degrees per second

    rate_gyr_x = (float) *gyr_raw * G_GAIN;

    rate_gyr_y = (float) *(gyr_raw+1) * G_GAIN;

    rate_gyr_z = (float) *(gyr_raw+2) * G_GAIN;

    //Calculate the angles from the gyro

    gyroXangle+=rate_gyr_x*DT;

    gyroYangle+=rate_gyr_y*DT;

    gyroZangle+=rate_gyr_z*DT;

    //Convert Accelerometer values to degrees

    AccXangle = (float) (atan2(*(acc_raw+1),*(acc_raw+2))+M_PI)*RAD_TO_DEG;

    AccYangle = (float) (atan2(*(acc_raw+2),*acc_raw)+M_PI)*RAD_TO_DEG;

        AccZangle = (float) (atan2(*(acc_raw),*acc_raw+1)+M_PI)*RAD_TO_DEG;

    //Change the rotation value of the accelerometer to -/+ 180

    if (AccXangle >180)

    {

        AccXangle -= (float)360.0;

    }

    if (AccYangle >180)

        {

        AccYangle -= (float)360.0;

        }

    if (AccZangle >180)

        AccZangle -= (float)360.0;

        // Complementary filter used to combine the accelerometer and gyro values.

    CFangleX=AA*(CFangleX+rate_gyr_x*DT) +(1 - AA) * AccXangle;

    CFangleY=AA*(CFangleY+rate_gyr_y*DT) +(1 - AA) * AccYangle;

        CFangleZ=AA*(CFangleZ+rate_gyr_z*DT) +(1 - AA) * AccZangle;

    

        filter_xterm[0] = (AccXangle - CFangleX) * timeConstant * timeConstant;

    filter_yterm[0] = (AccYangle - CFangleY) * timeConstant * timeConstant;

        filter_zterm[0] = (AccZangle - CFangleZ) * timeConstant * timeConstant;

      filter_xterm[2] = (DT * filter_xterm[0]) + filter_xterm[2];

      filter_yterm[2] = (DT * filter_yterm[0]) + filter_yterm[2];

        filter_zterm[2] = (DT * filter_zterm[0]) + filter_zterm[2];

      filter_xterm[1] = filter_xterm[2] + (AccXangle - CFangleX) * 2 * timeConstant + rate_gyr_x;

      filter_yterm[1] = filter_yterm[2] + (AccYangle - CFangleY) * 2 * timeConstant + rate_gyr_y;

        filter_zterm[1] = filter_zterm[2] + (AccZangle - CFangleZ) * 2 * timeConstant + rate_gyr_z;

      CFangleX2 = (DT * filter_xterm[1]) + CFangleX2;

      CFangleY2 = (DT * filter_yterm[1]) + CFangleY2;

        CFangleZ2 = (DT * filter_zterm[1]) + CFangleZ2;

        

 --------------- ******* current_time()- start_time= DT

                         while

                              (DT < 20 )

      ***exemple                  delay(10) ;

       

        //Each loop should be at least 20ms.

      

    }

}