volatile int rpm = 0;
int lastInputEventTime = -10 * CH_FREQUENCY;

void icuWidthCallback(ICUDriver *driver) {
    int now = chTimeNow();
    int diff = now - lastInputEventTime;
    rpm = 60000 * TICKS_IN_MS * 2 / 4 / diff;
    lastInputEventTime = now;
}

ICUConfig wave_icucfg = { ICU_INPUT_ACTIVE_LOW, 100000, icuWidthCallback, NULL };

int main(void) {
    halInit();
    chSysInit();

    // this thread would blink one of the LEDs, that would look cool
    chThdCreateStatic(blinkingThreadStack, sizeof(blinkingThreadStack), NORMALPRIO, blinkingThread, NULL);

    // serial-over-usb initialization
    usb_serial_start();

    // configure input signal pin
    palSetPadMode(CRANK_INPUT_PORT, CRANK_INPUT_PIN, PAL_MODE_ALTERNATE(GPIO_AF_TIM2));

    // start input capture - we will handle input events and calculate RPM based on the timestamps
    icuStart(&CRANK_DRIVER, &wave_icucfg);
    icuEnable(&CRANK_DRIVER);

    while (TRUE) {
        // RPM value is updated by the input event handler
        chprintf(&SDU1, "rpm: %d\r\n", rpm);
        chThdSleep(100);
    }

    return 0;
}