ch32v307_millis.c

/*
    If systemclock is 144MHz, this generates an interrupt every millisecond

*/
void init_millis() { 
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6, ENABLE);

    TIM6->PSC = 2;   // 144MHz / (65536 - 48000) / (2+1) = 1 milliseconds per tick

    TIM6->DMAINTENR = TIM_UIE;
    
    TIM6->ATRLR = 48000;

    TIM6->CTLR1 = TIM_ARPE | TIM_URS | TIM_CEN;

    NVIC_InitTypeDef  NVIC_InitStructure = {0};
    NVIC_InitStructure.NVIC_IRQChannel = TIM6_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    TIM6->INTFR = 0;
    NVIC_Init(&NVIC_InitStructure);
}

volatile uint64_t millis;

void TIM6_IRQHandler(void) __attribute__((interrupt("WCH-Interrupt-fast")));

void TIM6_IRQHandler(void) {
    millis++;
    TIM6->INTFR = 0;
}