RIT usage of LPC1768

In addition to the system tick timer and the general timer, LPC1768 also introduces a timer called the repetitive timer RIT. This timer can only be used for timing operations and has an interrupt. I personally feel that this seems to be a timer designed for delay functions.

So what process is followed when using this timer?

First, turn on the clock

Second, we need to determine the timer's frequency division value from pclk, which depends on another register

Third, turn off the timer first

Fourth set register comparison value

Fifth, clear or mask some specific comparison mask bits

Finally, turn on the interrupt and start the timer

#define RIT_INT_POSITION 0

#define RIT_ENCLR_POSITION 1

#define RIT_ENBR_POSITION 2

#define RIT_EN_POSITION 3

void RitInit(u32 count)

{

    LPC_SC->PCONP |=(1<<16); //Turn on the clock sys, divide by four to 25M

    LPC_RIT->RICTRL &= ~(1<<3);

    LPC_RIT->RICOMPVAL = count;

// LPC_RIT->RIMASK = count;

    LPC_RIT->RIMASK = 0x80000000;

    LPC_RIT->RICOUNTER = 0;

    NVIC_EnableIRQ(RIT_IRQn); /* enable irq in nvic */

    LPC_RIT->RICTRL = (1<

}

Finally, we need to respond to the interrupt in rit's interrupt function, as follows

void RIT_IRQHandler()

{

    u8 state = LPC_RIT->RICTRL;

    if(state&0x01) //An interrupt occurs

    {

        RitStop();

        LPC_RIT->RICOUNTER = 0;

        LPC_RIT->RICTRL |= 0x01; // Clear interrupt

        RIT_INT_CALLBACK;

        RitStart();

    }

}