PSOC5LP Jitter in interrupt handling

[Anonymous]

Hello,

   

I am just starting with CY8CKIT-050 Development Kit.

   

I am using two SAR-ADC (Sampling frequency 100 kHz) and some time-critical calculation in a hight priority interrupt service routine (prio 0). Everything works fine until I implement an additional interrupt service (rising edge @ 10Hz, priority 7) to set a flag for further processing. This further processing is done in den main-loop and sends some data to the display.

   

When the the low level interrupt is enabled, I measure a Jitter (about 1.3us) in the signal processing in the high-priority interrupt service routine.

   

This is done with a toggle Bit as digital output at the end of the routine. The service routine is triggered by eoc of one ADC and needs about 4 us for the signal processing (without code optimization).

   

The reason for this Jitter is the code in the main loop (LCD functions) :

   

CY_ISR(DISP_ISR_LOC)
{
  Disp_Flag = 1; 
}

   

int main(void) .....

   

         if (Disp_Flag == 1)
        {
            // Doing nothing for testing!
           
            phi_disp = (phi_LUT_int * (uint64)360000) >> 16; // für P = 2
                   
            sprintf(displayStr,"%4d %4d ",(int)voltCount_sin,(int)voltCount_cos);
            LCD_Position(0,0);
            LCD_PrintString(displayStr);
            result = sprintf(displayStr,"%6d mGrad",(int)phi_disp);
            LCD_Position(1,0);
            LCD_PrintString(displayStr);
            Disp_Flag = 0;
        }

   

There is also a Jitter in the signal processing, depending on the input signal values and the adjustment of code optimization. But with constant input values (ignoring the ADC-Data) this jitter is not existing.

   

Could you give me some hints for solving this problem? 

   

with regards

   

steve_c