GPIO timing issue in Timer ISR

[RN_it]

Posted on May 18, 2018 at 12:11

Hello ,

I am toggling a gpio inside the timer ISR . the timer ISR triggers for every 1 sec.

Actually i am not able to see perfect 1 sec of gpio toggling . it also differs at different AHB frequency . i have included 2 cases with snapshot. please help me understand why i can not get perfect 1 sec gpio toggling and why it is different at 2 different ahb frequencies .

In the ISR i am just doing GPIOC->ODR ^= 0x2000U;

case 1 : AHB = 16Mhz HSI, Prescaler of timer = 999, period = 15999  ( in the image there is a difference of 10ms)

case 2 : AHB= 50Mhz, Timer clock = 50Mhz, Prescaler of timer = 999, period = 49999 ( in the image there is a difference of 25ms)

In both case it is showing different output . 

[Nigel Meijer]

Posted on May 18, 2018 at 12:51

A few things have effect on the crystal, Like temperature and supply voltage.

For example in the STM32L083CZ datasheet on page 87:

MSI oscillator frequency drift   0 °C ≤ TA ≤ 85 °C -  ±3

A temperature between 0 and 85 degrees could cause a frequency drift of plus minus 3%

Same happens with the supply voltage.

Dont know why with different settings you get a different timing..

[Tesla DeLorean]

Posted on May 18, 2018 at 14:25

Hard to replicate from screen shots. Define which STM32, and show code.

Using HSE clock source?

Can you try with a calibrated scope?

Can you output internal clocks (HSI, HSE, PLL, etc) via MCO pin PA8, and scope those?

[RN_it]

Posted on May 18, 2018 at 15:23

 ,

 ,

Hello Clive , ,

Thanks for the reply . ,

i am using stm32f446re nucleo board . , not using HSE. ,

i am using saleae logic usb logic analyzer . i dont have a calibrated scope.

HSI is 16Mhz verified using MCO. on MCO pin i can measure precisely ,

here is code i used. ,

int main(void)

 ,

{

 ,

 ,

HAL_Init(),

SystemClock_Config(SYS_CLOCK_FREQ_50_MHZ),

 ,

 ,

TIMER_Init(),

 ,

 ,

GPIO_Init(),

 ,

 ,

HAL_TIM_Base_Start_IT(&,htim6),

 ,

 ,

while(1),

 ,

 ,

return 0,

 ,

}

void GPIO_Init(void)

 ,

{

 ,

/* GPIO Ports Clock Enable */

 ,

__HAL_RCC_GPIOC_CLK_ENABLE(),

 ,

__HAL_RCC_GPIOH_CLK_ENABLE(),

 ,

__HAL_RCC_GPIOA_CLK_ENABLE(),

 ,

__HAL_RCC_GPIOB_CLK_ENABLE(),

 ,

 ,

GPIO_InitTypeDef gpio_button,

 ,

gpio_button.Mode = GPIO_MODE_OUTPUT_PP,

 ,

gpio_button.Pin = GPIO_PIN_13,

 ,

gpio_button.Pull = GPIO_NOPULL,

 ,

gpio_button.Speed = GPIO_SPEED_FREQ_LOW,

 ,

HAL_GPIO_Init(GPIOC,&,gpio_button),

 ,

}

void TIMER_Init(void)

 ,

{

TIM_MasterConfigTypeDef sMasterConfig,

 ,

htim6.Instance = TIM6,

 ,

htim6.Init.Prescaler = 999,

 ,

htim6.Init.CounterMode = TIM_COUNTERMODE_UP,

 ,

htim6.Init.Period = (50000-1),

 ,

htim6.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1,

 ,

if (HAL_TIM_Base_Init(&,htim6) != HAL_OK)

 ,

{

 ,

_Error_Handler(__FILE__, __LINE__),

 ,

}

 ,

sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET,

 ,

sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE,

 ,

if (HAL_TIMEx_MasterConfigSynchronization(&,htim6, &,sMasterConfig) != HAL_OK)

 ,

{

 ,

_Error_Handler(__FILE__, __LINE__),

 ,

}

 ,

 ,

}

void SystemClock_Config(uint8_t clock_freq)

 ,

{

 ,

♯ if 1

 ,

RCC_OscInitTypeDef RCC_OscInitStruct,

 ,

RCC_ClkInitTypeDef RCC_ClkInitStruct,

 ,

 ,

/**Configure the main internal regulator output voltage

 ,

*/

 ,

__HAL_RCC_PWR_CLK_ENABLE(),

//__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3),

 ,

 ,

RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI,

 ,

RCC_OscInitStruct.HSIState = RCC_HSI_ON,

 ,

RCC_OscInitStruct.HSICalibrationValue = 16,

 ,

RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON,

 ,

RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI,

switch(clock_freq)

 ,

{

 ,

case SYS_CLOCK_FREQ_50_MHZ:

 ,

RCC_OscInitStruct.PLL.PLLM = 8,

 ,

RCC_OscInitStruct.PLL.PLLN = 50,

 ,

RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2,

 ,

RCC_OscInitStruct.PLL.PLLQ = 2,

 ,

RCC_OscInitStruct.PLL.PLLR = 2,

 ,

 ,

RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK

 ,

|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2,

 ,

RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK,

 ,

RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1,

 ,

RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2,

 ,

RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1,

 ,

break,

 ,

 ,

case SYS_CLOCK_FREQ_84_MHZ:

 ,

RCC_OscInitStruct.PLL.PLLM = 8,

 ,

RCC_OscInitStruct.PLL.PLLN = 84,

 ,

RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2,

 ,

RCC_OscInitStruct.PLL.PLLQ = 2,

 ,

RCC_OscInitStruct.PLL.PLLR = 2,

 ,

 ,

RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK

 ,

|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2,

 ,

RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK,

 ,

RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1,

 ,

RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2,

 ,

RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1,

 ,

break,

 ,

 ,

case SYS_CLOCK_FREQ_120_MHZ:

 ,

RCC_OscInitStruct.PLL.PLLM = 8,

 ,

RCC_OscInitStruct.PLL.PLLN = 120,

 ,

RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2,

 ,

RCC_OscInitStruct.PLL.PLLQ = 2,

 ,

RCC_OscInitStruct.PLL.PLLR = 2,

 ,

 ,

RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK

 ,

|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2,

 ,

RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK,

 ,

RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1,

 ,

RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4,

 ,

RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2,

 ,

break,

 ,

 ,

default:

 ,

return ,

 ,

 ,

}

 ,

 ,

if (HAL_RCC_OscConfig(&,RCC_OscInitStruct) != HAL_OK)

 ,

{

 ,

_Error_Handler(__FILE__, __LINE__),

 ,

}

 ,

 ,

 ,

 ,

if (HAL_RCC_ClockConfig(&,RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)

 ,

{

 ,

_Error_Handler(__FILE__, __LINE__),

 ,

}

 ,

 ,

 ,

/**Configure the Systick interrupt time

 ,

*/

 ,

uint32_t hclk_freq = HAL_RCC_GetHCLKFreq(),

 ,

HAL_SYSTICK_Config(hclk_freq/1000),

/**Configure the Systick

 ,

*/

 ,

HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK),

/* SysTick_IRQn interrupt configuration */

 ,

HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0),

}

/**

 ,

* @brief This function handles TIM6 global interrupt and DAC1, DAC2 underrun error interrupts.

 ,

*/

 ,

void TIM6_DAC_IRQHandler(void)

 ,

{

 ,

/* USER CODE BEGIN TIM6_DAC_IRQn 0 */

 ,

 ,

//HAL_GPIO_TogglePin(GPIOA,GPIO_PIN_5),

 ,

//GPIOC->,ODR ^= 0x2000U,

 ,

GPIOC->,ODR ^= 0x2000U,

 ,

/* USER CODE END TIM6_DAC_IRQn 0 */

 ,

HAL_TIM_IRQHandler(&,htim6),

 ,

/* USER CODE BEGIN TIM6_DAC_IRQn 1 */

/* USER CODE END TIM6_DAC_IRQn 1 */

 ,

}

[Tesla DeLorean]

Posted on May 18, 2018 at 15:29

The Nucleo should be able to source an 8 MHz HSE via the ST-LINK

The TIM should be able to drive a pin in toggle mode directly

[John Craven]

Posted on May 19, 2018 at 17:37

From the manual;

6.2.2 HSI clock

...

Calibration

RC oscillator frequencies can vary from one chip to another due to manufacturing process variations, this is why each device is factory calibrated by ST for 1% accuracy at TA= 25 °C.

Yor are getting results close to the factory specification.

Have you calibrated the HSI better than 1%?

Using HSE from ST-link on nucleo boards has always be much better than HSI in my experience (12-15 boards).