Why is the LED blinking without any physical interrupt? - embedded

Question

The following is the interrupt handler for LED0 to toggle when an interrupt occurs on the UART0 due to LIN transmission from master to slave, my device is the slave. But without connecting my device(slave) to the master that means without any LIN transmission over UART, the LED0 is toggling. I cannot understand, how can this happen automatically? How can an interrupt be generated and Toggle of LED0 can happen?
void FTM0_IRQHandler()
{
if (1==((FTM0_C0SC & FTM_CnSC_CHF_MASK)>>FTM_CnSC_CHF_SHIFT) ) /* If the CHF of the channel is equal to 0 */
{
(void)FTM0_C0SC; /* Read to clear flag */
FTM0_C0SC ^= FTM_CnSC_CHF_MASK; /* Clear flag */
FTM0_C0V = FTM0_C0V + 391 ; /* Refresh interrupt period */
if (LED_counter>=50){
/* Toggle LED for LIN transmission */
/* Reset counter */
LED0_TOGGLE;
LED_counter = 0;
}
LED_counter++;
}
}
In my main funtion I have called my timer initialization as follows:
lin_application_timer_FTM0();
And the above function is defined as follows:
void lin_application_timer_FTM0()
{
SIM_SCGC |= SIM_SCGC_FTM0_MASK; /* Enable Clock for FTM0 */
FTM0_SC |= FTM_SC_PS(7); /* Select Preescaler in this case 128. 20 Mhz /128 =156.25 Khz. */
/* Counter increase by one every 6.4 us */
/* Enable Channle 0*/
FTM0_C0SC |= FTM_CnSC_CHIE_MASK; /* Enable channel 0 interrupt */
FTM0_C0SC |= FTM_CnSC_MSA_MASK; /* Channel as Output compare mode */
/*Select interrupt frequency*/
FTM0_C0V = FTM_CnV_VAL(391) ; /* Interrupt every 2.5ms */
FTM0_SC |= FTM_SC_CLKS(1); /*FTM0 use system clock*/
/* Set the ICPR and ISER registers accordingly */
NVIC_ICPR |= 1 << ((INT_FTM0-16)%32);
NVIC_ISER |= 1 << ((INT_FTM0-16)%32);
}
Can anyone explain why is the LED0 toggling without any interrupt?

Answer 1

It’s possible that the interrupt is actually being triggered. Does your interrupt pin have a pull up or pull-down resistor attached? If it’s disconnected and just “floating”, electrical noise in the environment can cause spurious interrupts.