/**
* @brief Main program
* @param None
* @retval None
*/
int main(void)
{
/* STM32F4xx HAL library initialization:
- Configure the Flash prefetch, instruction and Data caches
- Configure the Systick to generate an interrupt each 1 msec
- Set NVIC Group Priority to 4
- Global MSP (MCU Support Package) initialization
*/
HAL_Init();
/* Configure the system clock to 168 MHz */
SystemClock_Config();
/* Configure LED3 */
BSP_LED_Init(LED3);
/*##-1- Configure the TIM peripheral #######################################*/
/* -----------------------------------------------------------------------
TIM1 Configuration: generate 1 PWM signal using the DMA burst mode:
TIM1 input clock (TIM1CLK) is set to 2 * APB2 clock (PCLK2),
since APB2 prescaler is different from 1.
TIM1CLK = 2 * PCLK2
PCLK2 = HCLK / 2
=> TIM1CLK = 2 * (HCLK / 2) = HCLK = SystemCoreClock
To get TIM1 counter clock at 24 MHz, the prescaler is computed as follows:
Prescaler = (TIM1CLK / TIM1 counter clock) - 1
Prescaler = (SystemCoreClock /24 MHz) - 1
The TIM1 period is 5.8 KHz: TIM1 Frequency = TIM1 counter clock/(ARR + 1)
= 24 MHz / 4096 = 5.85 KHz
TIM1 Channel1 duty cycle = (TIM1_CCR1/ TIM1_ARR)* 100 = 33.33%
Note:
SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f4xx.c file.
Each time the core clock (HCLK) changes, user had to update SystemCoreClock
variable value. Otherwise, any configuration based on this variable will be incorrect.
This variable is updated in three ways:
1) by calling CMSIS function SystemCoreClockUpdate()
2) by calling HAL API function HAL_RCC_GetSysClockFreq()
3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency
----------------------------------------------------------------------- */
TimHandle.Instance = TIMx;
TimHandle.Init.Period = 0xFFFF;
TimHandle.Init.RepetitionCounter = 0;
TimHandle.Init.Prescaler = (uint16_t) ((SystemCoreClock / 24000000) - 1);
TimHandle.Init.ClockDivision = 0;
TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;
if(HAL_TIM_PWM_Init(&TimHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/*##-2- Configure the PWM channel 3 ########################################*/
sConfig.OCMode = TIM_OCMODE_PWM1;
sConfig.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfig.Pulse = 0xFFF;
if(HAL_TIM_PWM_ConfigChannel(&TimHandle, &sConfig, TIM_CHANNEL_1) != HAL_OK)
{
/* Configuration Error */
Error_Handler();
}
/*##-3- Start PWM signal generation in DMA mode ############################*/
if( HAL_TIM_PWM_Start(&TimHandle, TIM_CHANNEL_1) != HAL_OK)
{
/* Starting PWM generation Error */
Error_Handler();
}
/*##-4- Start DMA Burst transfer ###########################################*/
HAL_TIM_DMABurst_WriteStart(&TimHandle, TIM_DMABASE_ARR, TIM_DMA_UPDATE,
(uint32_t*)aSRC_Buffer, TIM_DMABURSTLENGTH_3TRANSFERS);
/* Infinite loop */
while (1)
{
}
}
/**
* @brief Main program.
* @param None
* @retval None
*/
int main(void)
{
/* Enable the CPU Cache */
CPU_CACHE_Enable();
/* STM32F7xx HAL library initialization:
- Configure the Flash ART accelerator on ITCM interface
- Systick timer is configured by default as source of time base, but user
can eventually implement his proper time base source (a general purpose
timer for example or other time source), keeping in mind that Time base
duration should be kept 1ms since PPP_TIMEOUT_VALUEs are defined and
handled in milliseconds basis.
- Set NVIC Group Priority to 4
- Low Level Initialization
*/
HAL_Init();
/* Configure the system clock to 216 MHz */
SystemClock_Config();
/* Configure LED3 */
BSP_LED_Init(LED3);
/*##-1- Configure the TIM peripheral #######################################*/
/* -----------------------------------------------------------------------
TIM2 Configuration: generate 1 PWM signal using the DMA burst mode:
TIM2 input clock (TIM2CLK) is set to APB1 clock (PCLK1)x2, since APB1
prescaler is 4.
TIM1CLK = PCLK1/2
PCLK1 = HCLK/4
=> TIM1CLK = HCLK/2 = SystemCoreClock/2
To get TIM2 counter clock at 20 MHz, the prescaler is computed as follows:
Prescaler = (TIM2CLK / TIM2 counter clock) - 1
Prescaler = ((SystemCoreClock/2) /20 MHz) - 1
The TIM2 Frequency = TIM2 counter clock/(ARR + 1)
= 20 MHz / 4096 = 4.88 KHz
TIM2 Channel1 duty cycle = (TIM2_CCR1/ TIM2_ARR)* 100 = 33.33%
Note:
SystemCoreClock variable holds HCLK frequency and is defined in stm32f7xxxx.c file.
Each time the core clock (HCLK) changes, user had to update SystemCoreClock
variable value. Otherwise, any configuration based on this variable will be incorrect.
This variable is updated in three ways:
1) by calling CMSIS function SystemCoreClockUpdate()
2) by calling HAL API function HAL_RCC_GetSysClockFreq()
3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency
----------------------------------------------------------------------- */
TimHandle.Instance = TIM2;
TimHandle.Init.Period = 0xFFFF;
TimHandle.Init.Prescaler = ((SystemCoreClock/2) / (20 * 1000000)) - 1;
TimHandle.Init.ClockDivision = 0;
TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;
if(HAL_TIM_PWM_Init(&TimHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/*##-2- Configure the PWM channel 1 ########################################*/
sConfig.OCMode = TIM_OCMODE_PWM1;
sConfig.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfig.Pulse = 0xFFF;
if(HAL_TIM_PWM_ConfigChannel(&TimHandle, &sConfig, TIM_CHANNEL_1) != HAL_OK)
{
/* Configuration Error */
Error_Handler();
}
/*##-3- Start PWM signal generation in DMA mode ############################*/
if( HAL_TIM_PWM_Start(&TimHandle, TIM_CHANNEL_1) != HAL_OK)
{
/* Starting PWM generation Error */
Error_Handler();
}
/*##-4- Start DMA Burst transfer ###########################################*/
HAL_TIM_DMABurst_WriteStart(&TimHandle, TIM_DMABASE_ARR, TIM_DMA_UPDATE,
(uint32_t*)aSRC_Buffer, TIM_DMABURSTLENGTH_3TRANSFERS);
/* Infinite loop */
while (1)
{
}
}
