Generating a delay of 5 microseconds using STM32F407VG Discovery board?

Forum|Forum|7 years ago
February 20, 2019
10 replies
3076 views

Dear All,

I need to a get a delay of 5 microseconds using STM32F407VG Discovery board.

Is using a timer a good option for this or there is other ways available to solve the problem without using any external library?

STM32F4 series

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MNapi

Senior II

I looked at this before there seems to be only one function HAL_Delay(); which gives you only milliseconds.

The only way I see is to use

for (int i=1; i<1000; i++)

{}

but you need to find a way to measure how many you need. They way I did is. I connected oscilocope

and I do turn a pin high and low before and after the loop to measure fequency.

HAL_GPIO_WritePin and you use SET and RESET to turn it on and off

GSING.19Author

Associate II

Is using timer here a good idea?

MNapi

Senior II

I do not know how you want to implement the times as interrupt ? you could use PWM to get 5 microseconds

then you could use to jump on falling or rising to: and do whatever you need inside.

HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)

{}

S.Ma

Principal

I guess you just want 5+ usec delay?

Is this delay triggering HW activity or not?

If it's pure SW, if you are just Waiting for 5+ usec delays you can use a SW delay with NOPs.

The number of loops depends on SYSCLK frequency.

GSING.19Author

Associate II

I have sensor in order to activate that sensor I need to held line low for 5 microseconds.

Peter Mather

Associate III

#define SetupTime 25
void uSec(int us) {
 us=us*(PeripheralBusSpeed/1000000)-SetupTime;
 __HAL_TIM_SET_COUNTER(&htim2, 0);
 while (__HAL_TIM_GET_COUNTER(&htim2)<us);
}

In most of my applications I set up a 32-bit timer (TIM2) freerunning at bus speed. Then I can use it for any short delays

/* TIM2 init function */
static void MX_TIM2_Init(void)
{
 
 TIM_ClockConfigTypeDef sClockSourceConfig;
 TIM_MasterConfigTypeDef sMasterConfig;
 
 htim2.Instance = TIM2;
 htim2.Init.Prescaler = 0;
 htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim2.Init.Period = 0xFFFFFFFF;
 htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
 htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
 if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 
 sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
 if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 
}

unsigned long readusclock(void){
	return __HAL_TIM_GET_COUNTER(&htim2)/(PeripheralBusSpeed/1000000);
}
void initusclock(void){
	__HAL_TIM_SET_COUNTER(&htim2, 0);
}