- Ask a related questionWhat is a related question?A related question is a question created from another question. When the related question is created, it will be automatically linked to the original question.
The problem is that I use CPU timer 1 to trigger ADC conversion. If the timer is configured faster than 35us (for example 30us), once in a while the end of conversion interrupt is triggered two times. The interrupt takes less than 2us to run. If I use 35us then I don't have double pulses. I will assert a GPIO-pin at a first line in interrupt and set it at the end. To measure times I use oscilloscope. What could be the limitation? The ADC interrupt has the highest priority.
Initialization:
EALLOW;
CpuSysRegs.PCLKCR13.bit.ADC_A = 1;
(*Device_cal)();
EDIS;
// Setup VREF as internal
SetVREF(ADC_ADCA, ADC_INTERNAL, ADC_VREF3P3);
EALLOW;
// Set ADCCLK divider to /4
AdcaRegs.ADCCTL2.bit.PRESCALE = 6;
// Set pulse positions to late
AdcaRegs.ADCCTL1.bit.INTPULSEPOS = 1;
// Power up the ADC and then delay for 1 ms
AdcaRegs.ADCCTL1.bit.ADCPWDNZ = 1;
EDIS;
DELAY_US(1000);
// Configure SOC
EALLOW;
AdcaRegs.ADCSOC0CTL.bit.CHSEL = 1; // SOC0 will convert pin A1
// 0:A0 1:A1 2:A2 3:A3
// 4:A4 5:A5 6:A6 7:A7
// 8:A8 9:A9 A:A10 B:A11
// C:A12 D:A13 E:A14 F:A15
AdcaRegs.ADCSOC0CTL.bit.ACQPS = 9; // Sample window is 10 SYSCLK cycles
AdcaRegs.ADCSOC0CTL.bit.TRIGSEL = 2; // Trigger on CPU1 Timer 1, TINT1n
AdcaRegs.ADCINTSEL1N2.bit.INT1SEL = 0; // End of SOC0 will set INT1 flag
AdcaRegs.ADCINTSEL1N2.bit.INT1E = 1; // Enable INT1 flag
AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1; // Make sure INT1 flag is cleared
// Enable ADCINT1 in PIE
PieCtrlRegs.PIEIER1.bit.INTx1 = 1; // Enable INT 1.1 in the PIE
IER |= M_INT1; // Enable CPU Interrupt 1
EDIS;
// Configure CPU1 Timer 1
// Enable clock for CPU1 timer 1
EALLOW;
CpuSysRegs.PCLKCR0.bit.CPUTIMER1 = 1;
EDIS;
// CPU Frequency in MHz, period in uSeconds
ConfigCpuTimer(&CpuTimer1, 100000000 / 1000000U, 30);
// Start timer
CpuTimer1Regs.TCR.all = 0x4000;Interrupt:
__interrupt void ADC_isr(void)
{
GpioDataRegs.GPACLEAR.bit.GPIO8 = 1;
// Set interrupt priority:
volatile Uint16 TempPIEIER = PieCtrlRegs.PIEIER1.all;
IER |= M_INT1;
IER &= MINT1; // Set "global" priority
PieCtrlRegs.PIEIER1.all &= MG11; // Set "group" priority
PieCtrlRegs.PIEACK.all = 0xFFFF; // Enable PIE interrupts
asm(" NOP"); // Wait for PIEACK to exit the pipeline
EINT;
some code.... (takes less than 2us)
// Clear the interrupt flag
AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1;
GpioDataRegs.GPASET.bit.GPIO8 = 1;
// Restore registers saved:
DINT;
PieCtrlRegs.PIEIER1.all = TempPIEIER;
}JHi
I did two measurements and I have attached the oscilloscope images of them. The pin will be set in a timer 1 interrupt and cleared when the ADC end of conversion interrupt is ready. In a first picture the timer is 35us and in a second one 20us. I really can't understand why in the second image the interrupt seems to take so much longer.
JHi
