STM32F042 定时器17CH1 PWM输出问题

ct3paul · 发表于 2017-3-22 10:21:05

各位：
我在做使用STM32F042 定时器17通道1 输出5MHZ方波，占空比为50%时，输出的波形为5.336MHZ，占空比约为33%
但是输出较小频率是稳定，如2MHZ，示波器测量就正确，麻烦各位解答下
是否是超出输出上限了？
系统时钟为48M，HCLK、PCLK均未分频，为48M
附TIM17设置代码：[mw_shl_code=c,true]void TIM17_CH1_PWM(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
uint16_t TimerPeriod;
uint16_t Channel1Pulse;

//RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM16 | RCC_APB2Periph_TIM17,ENABLE);
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB,ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM17,ENABLE);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource9, GPIO_AF_2);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOB, &GPIO_InitStructure);

TimerPeriod = (SystemCoreClock / 5000000 ) - 1;
//Compute CCR1 value to generate a duty cycle at 50% for channel 1 and 1N
Channel1Pulse = (uint16_t) (((uint32_t) 50 * (TimerPeriod - 1)) / 100);

//Time Base configuration
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM17, &TIM_TimeBaseStructure);

//Channel 1, 2,3 and 4 Configuration in PWM mode
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
TIM_OCInitStructure.TIM_Pulse = Channel1Pulse;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;

TIM_OC1Init(TIM17, &TIM_OCInitStructure);
TIM_Cmd(TIM17, ENABLE);
TIM_CtrlPWMOutputs(TIM17, ENABLE);
}[/mw_shl_code]
原子哥，求解答。