Wave generation of particular frequency.

[LACTIC]

By using timer I want to generate a wave of 27Mhz frequency. Present time I can generate only 13.48khz frequency wave. My timer settings are below please tell me how can I generate it.

static void MX_TIM2_Init(void)

{

 TIM_ClockConfigTypeDef sClockSourceConfig;

 TIM_MasterConfigTypeDef sMasterConfig;

 TIM_OC_InitTypeDef sConfigOC;

 htim2.Instance = TIM2;

 htim2.Init.Prescaler =27;

 htim2.Init.CounterMode = TIM_COUNTERMODE_UP;

 htim2.Init.Period = 1000;

 htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV4;

 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__);

 }

 if (HAL_TIM_OC_Init(&htim2) != 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__);

 }

 sConfigOC.OCMode = TIM_OCMODE_TOGGLE;

 sConfigOC.Pulse = 250;

 sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;

 sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;

 if (HAL_TIM_OC_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_4) != HAL_OK)

 {

  _Error_Handler(__FILE__, __LINE__);

 }

 HAL_TIM_MspPostInit(&htim2);

}

[LACTIC]

Please suggest how can in  generate a wave of 27Mhz frequency. Timer settings are mentioned in above massage.

[RomainR.]

Hello,

Can you please detail which STM32 device, and APB Clock frequency you have set ?

Change htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;

Not TIM_CLOCKDIVISION_DIV4;

27MHz / 4 = 6.75 which is the half of 13.5MHz you measure.

BR

rrom

[LACTIC]

Hello,

Ok. I will cange it.

I am using STM32f207ZGT6.

[LACTIC]

Sorry it is "change" not cange.

[S.Ma]

if you core runs at 108 MHz and say this goes direct to feed timer clock, your timer can count only up to 4 as period.

Then set the toggle point to 2 and you get 50% duty cycle at 27MHz.

0123012301230123

__--__--__--__--__

Or more fun, if you use a SPI as master with DMA cyclical to a dummy buffer, its maximum clock SCK will run at SYSCLK/2 = 54 MHz (if fast SPI, STM32 family dependent)

[LACTIC]

System clock settings :-

void SystemClock_Config(void)

{

 RCC_OscInitTypeDef RCC_OscInitStruct;

 RCC_ClkInitTypeDef RCC_ClkInitStruct;

  /**Initializes the CPU, AHB and APB busses clocks 

  */

 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;

 RCC_OscInitStruct.HSEState = RCC_HSE_ON;

 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;

 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;

 RCC_OscInitStruct.PLL.PLLM = 4;

 RCC_OscInitStruct.PLL.PLLN = 216;

 RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV4;

 RCC_OscInitStruct.PLL.PLLQ = 4;

 if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)

 {

  _Error_Handler(__FILE__, __LINE__);

 }

  /**Initializes the CPU, AHB and APB busses clocks 

  */

 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_DIV8;

 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)

 {

  _Error_Handler(__FILE__, __LINE__);

 }

  /**Configure the Systick interrupt time 

  */

 HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

  /**Configure the Systick 

  */

 HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

 /* SysTick_IRQn interrupt configuration */

 HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);

}

[LACTIC]

cubmex clock config window.

[S.Ma]

Also look at MCU output pin, which can output internal clock with simple prescale factor. Simple cheap, keeps more complex peripherals available.

==> Reference Manual