Question
STM32F4-discovery DDS
Posted on April 07, 2015 at 15:43
Hi.
I try to make DDS. The code is below. The idea is to get new value of capture-compare register after Update event. This is done in the update interrupt. I have the following problems: 1) I do not see zero in the train of pulses, while it is present in the array; 2) I see some pulses which should not be (I attached the images - in the lower one is shown the marked pule of the upper image, only one pulse has such artifacts others pulses are ok ). How those problems can be solved? Maybe I should use one pulse mode? Thanks! /* My file as replacement for main.c of TIM_PWMOutput project This is DDS test Original main.c is excluded from compiling */ #include ''stm32f4xx.h'' TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; TIM_OCInitTypeDef TIM_OCInitStructure; /* Private variables ---------------------------------------------------------*/ uint16_t CCR1_Val = 350; uint16_t PrescalerValue = 0; int sinus[60]={349, 385, 422, 457, 491, 523, 554, 583, 608, 631, 651, 668, 681, 690, 696, 698, 696, 690, 681, 668, 651, 631, 608, 583, 554, 524, 491, 457, 422, 385, 349, 313, 276, 241, 207, 175, 144, 115, 90, 67, 47, 30, 17, 8, 2, 0, 2, 8, 17, 30, 47, 67, 90, 115, 144, 174, 207, 241, 276, 313}; void TIM_Config(void); void TIM4_IRQHandler(void); int main (void) { / /* TIM Configuration */ TIM_Config(); /* ----------------------------------------------------------------------- TIM4 Configuration: generate 4 PWM signals with 4 different duty cycles. In this example TIM4 input clock (TIM4CLK) is set to 4 * APB1 clock (PCLK1), since TIMPRE bit from RCC_DCKCFGR register is set. TIM4CLK = 4 * PCLK1 PCLK1 = HCLK / 4 => TIM4CLK = HCLK = SystemCoreClock To get TIM4 counter clock at 21 MHz, the prescaler is computed as follows: Prescaler = (TIM4CLK / TIM4 counter clock) - 1 Prescaler = (SystemCoreClock /21 MHz) - 1 To get TIM4 output clock at 30 KHz, the period (ARR)) is computed as follows: ARR = (TIM4 counter clock / TIM4 output clock) - 1 = 699 ----------------------------------------------------------------------- */ RCC_TIMCLKPresConfig(RCC_TIMPrescActivated); /* Compute the prescaler value */ PrescalerValue = (uint16_t) (SystemCoreClock / 21000000) - 1; /* Time base configuration */ TIM_TimeBaseStructure.TIM_Period = 699; TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); /* PWM1 Mode configuration: Channel1 */ TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; TIM_OCInitStructure.TIM_Pulse = CCR1_Val; TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; TIM_OC1Init(TIM4, &TIM_OCInitStructure); // TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable); // TIM_ARRPreloadConfig(TIM4, ENABLE); TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE); NVIC_InitTypeDef NVIC_InitStructure; NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); /* TIM4 enable counter */ TIM_Cmd(TIM4, ENABLE); while (1) {} } void TIM4_IRQHandler(void) { static int i = 0; i++; if (i == 60) i = 0; TIM4->CCR1 = sinus[i]; TIM_ClearFlag(TIM4, TIM_FLAG_Update); } void TIM_Config(void) { GPIO_InitTypeDef GPIO_InitStructure; /* TIM4 clock enable */ RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE); /* GPIOD clock enable */ RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE); /* GPIOD Configuration: TIM4 CH1 (PD12)*/ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ; GPIO_Init(GPIOD, &GPIO_InitStructure); /* Connect TIM4 pins to AF2 */ GPIO_PinAFConfig(GPIOD, GPIO_PinSource12, GPIO_AF_TIM4); }