HiFive1 Timer interrupt sample

HiFive1-Timer-interrupt.c

/* Standard includes */
#include <stdio.h>

/* HiFive1/FE310 includes */
#include "sifive/devices/spi.h"
#include "platform.h"
#include "encoding.h"
#include "plic/plic_driver.h"

volatile int invert_LEDs = 0;

void handle_m_time_interrupt()
{
    /* Disable the machine and timer interrupts until setup is completed */
    clear_csr(mie, MIP_MTIP);

    /* Set the machine timer to go off in X seconds */
    volatile uint64_t * mtime    = (uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIME);
    volatile uint64_t * mtimecmp = (uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIMECMP);
    uint64_t now = *mtime;
    /* Send data every second */
    uint64_t then = now + 100;
    *mtimecmp = then;

    /* Notify the main loop that it can now invert the LED output */
    invert_LEDs = 1;

    /* Re-enable timer */
    set_csr(mie, MIP_MTIP);
}

void handle_m_ext_interrupt()
{
}

void init_GPIO()
{
    GPIO_REG(GPIO_OUTPUT_EN)  |=  (1 << GREEN_LED_OFFSET);
    GPIO_REG(GPIO_OUTPUT_VAL) |=  (1 << GREEN_LED_OFFSET);
}

void init_timer()
{
    clear_csr(mie, MIP_MTIP);

    volatile uint64_t * mtime    = (uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIME);
    volatile uint64_t * mtimecmp = (uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIMECMP);
    uint64_t now = *mtime;
    uint64_t then = now + 100;
    *mtimecmp = then;

    /* Enable timer and all interrupts */
    set_csr(mie, MIP_MTIP);
    set_csr(mstatus, MSTATUS_MIE);
}

int main()
{
    puts("Timer setup complete, periodically inverting the green LED ...");

    init_GPIO();
    init_timer();

    while (1) {
        if (invert_LEDs) {
            GPIO_REG(GPIO_OUTPUT_VAL) ^= (0x1 << GREEN_LED_OFFSET);
            invert_LEDs = 0;
        }
    };

    return 0;
}