CCS/TM4C123GH6PM: Tiva C triggering ADC by GPIO event

Tool/software: Code Composer Studio

Hello. I have next task. I receive 2 signals from compactors which looks like 50% PWM 100Hz and shifted by 90 degrees to each other. I need to make ADC sample each time than signals switched (4 times per period or 400hz). I wrote next code for this task.

static void adcInterruptHandler(){

    unsigned int state = ADCIntStatus(ADC0_BASE, 0, true);
    ADCIntClear(ADC0_BASE, 0);

    int32_t tmp[2];
    ADCSequenceDataGet(ADC0_BASE, 0, (uint32_t *)tmp);
    ADCSequenceDataGet(ADC0_BASE, 0, (uint32_t *)tmp+1);
}

static void initAdc(){
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);

    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_ADC0));

    ADCSequenceConfigure(ADC0_BASE, 0, ADC_TRIGGER_EXTERNAL, 0);
    //set up sequence
    ADCSequenceStepConfigure(ADC0_BASE, 0, 0, ADC_CTL_CH1);
    ADCSequenceStepConfigure(ADC0_BASE, 0, 1, ADC_CTL_CH0 |
                             ADC_CTL_IE | ADC_CTL_END);
    //interrupt settings
    ADCIntRegister(ADC0_BASE, 0, adcInterruptHandler);
    ADCIntEnable(ADC0_BASE, 0);
    ADCSequenceEnable(ADC0_BASE, 0);
    ADCIntClear(ADC0_BASE, 0);
}

static void initGpioInterrupt(){
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
    GPIOPinTypeGPIOInput(GPIO_PORTF_BASE, GPIO_PIN_0);
    GPIOPinTypeGPIOInput(GPIO_PORTF_BASE, GPIO_PIN_4);
    GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_0, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPU);
    GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_4, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPU);
    GPIOIntTypeSet(GPIO_PORTF_BASE,GPIO_PIN_0,GPIO_BOTH_EDGES);
    GPIOIntTypeSet(GPIO_PORTF_BASE,GPIO_PIN_4,GPIO_BOTH_EDGES);


    GPIOADCTriggerEnable(GPIO_PORTF_BASE, GPIO_PIN_0);
    GPIOADCTriggerEnable(GPIO_PORTF_BASE, GPIO_PIN_4);
}

This code run good while i emulate event using button, but at real enviroment it goes to FaultISR. Look like signals has gitter and triggering happend several times in one moment. I need to fix this fault by skipping redundant events but how to do it?