STM32 TIM8 PWM

TIM_CtrlPWMOutputs(TIM8, ENABLE);

//gpioc-9  is tim8ch4
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8|RCC_APB2Periph_GPIOC, ENABLE);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);

TIM_DeInit(TIM8);

//2.7K
TIM_BaseInitStructure.TIM_Period =370;
TIM_BaseInitStructure.TIM_Prescaler = 71;
TIM_BaseInitStructure.TIM_ClockDivision = 0;
TIM_BaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM8, &TIM_BaseInitStructure);

/* Output Compare Active Mode configuration: Channel4 */

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 185;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC4Init(TIM8, &TIM_OCInitStructure);
TIM_OC4PreloadConfig(TIM8, TIM_OCPreload_Enable);

TIM_ARRPreloadConfig(TIM8, ENABLE);
TIM_CtrlPWMOutputs(TIM8, ENABLE);
TIM_Cmd(TIM8,ENABLE);