Hi, I'm trying to understand what I'm doing wrong that the following function seems to delay by anywhere between 667ns and 5.67us even though it's being called as Delay_us(4)
I'm using Nucleo STM32F446RE
void KJO_TIM6_Init(uint16_t arel)
{
LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM6);
LL_TIM_InitTypeDef tim6init = {0};
//clock on APB1 is 40MHz so we need to reduce it by 40
//tim6init.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;
tim6init.Prescaler = 40;
tim6init.Autoreload = arel;
//tim6init.CounterMode = LL_TIM_COUNTERMODE_DOWN;
LL_TIM_Init(TIM6, &tim6init);
LL_TIM_SetOnePulseMode(TIM6, LL_TIM_ONEPULSEMODE_SINGLE);
LL_TIM_ClearFlag_UPDATE(TIM6);
}
void KJO_Delay_us(uint16_t delay)
{
LL_TIM_SetAutoReload(TIM6, delay);
LL_TIM_SetPrescaler(TIM6, 40); //it's cleared on each reload
LL_TIM_EnableCounter(TIM6); //one-pulse mode disables the counter
while(!LL_TIM_IsActiveFlag_UPDATE(TIM6));
LL_TIM_ClearFlag_UPDATE(TIM6);
}
The SysClk clock was configured to 160MHz using code generated with CubeMX, so as I understand TIM6 should take APB1 frequency which is 40MHz, prescale it by 40 to effectively give 1 MHz or 1us delay.
void SystemClock_Config(void)
{
LL_FLASH_SetLatency(LL_FLASH_LATENCY_5);
if(LL_FLASH_GetLatency() != LL_FLASH_LATENCY_5)
{
Error_Handler();
}
LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
LL_PWR_DisableOverDriveMode();
LL_RCC_HSI_SetCalibTrimming(16);
LL_RCC_HSI_Enable();
/* Wait till HSI is ready */
while(LL_RCC_HSI_IsReady() != 1)
{
}
LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_HSI, LL_RCC_PLLM_DIV_8, 160, LL_RCC_PLLP_DIV_2);
LL_RCC_PLL_Enable();
/* Wait till PLL is ready */
while(LL_RCC_PLL_IsReady() != 1)
{
}
LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_8);
LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_2);
LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_PLL);
/* Wait till System clock is ready */
while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_PLL)
{
}
LL_SetSystemCoreClock(160000000);
/* Update the time base */
if (HAL_InitTick (TICK_INT_PRIORITY) != HAL_OK)
{
Error_Handler();
};
LL_RCC_SetTIMPrescaler(LL_RCC_TIM_PRESCALER_TWICE);
}
My function is used to toggle a GPIO PIN to enable an LCD, but according to logic analyser it never time right.
Pin is configured this way
GPIO_InitStruct.Pin = LCD_RS_PIN|LCD_RW_PIN|LCD_EN_PIN;
GPIO_InitStruct.Mode = LL_GPIO_MODE_OUTPUT;
GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_MEDIUM;
GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
//GPIO_InitStruct.Pull = LL_GPIO_PULL_DOWN;
LL_GPIO_Init(GPIOB, &GPIO_InitStruct);
Does this approach even makes sense? I've seen other suggestions for creating microsecond delay functions, but I'm just trying to understand here how timers work. I used to use Atmel AVR chips which were much simpler than this one and I'm just lost.
Thanks in advance.
