Greetings,
I am currently toying around with the KEIL MCBSTM32F200 Evaluation Board (the STM32F207VG uC) and have run into some problems with the PWM output.
I want a simple PWM-signal on TIM1, Channel1 (PA8 for STM32F205&207) using the standard peripheral library for STM32Fxx.
The code below is a mix from the different examples from the standard peripheral library examples for PWM, and I'm sure something critical is missing.
After initializing, all TIM1 registers looks "ok" (as far as I can tell, the timer is a bit too advanced for me...) and the TIM1_CNT register is counting up and resetting.
When connecting the oscilloscope to PA8, all I get is a steady 3.3V signal, no PWM.
What am I missing here? It's quite frustrating since all other peripherals I'm using are working fine. Thanks in advance. (code also at Pastebin: http://pastebin.com/yUmZbXUL)
#include "stm32f2xx.h" #include "stm32f2xx_gpio.h" #include "stm32f2xx_rcc.h" #include "stm32f2xx_tim.h" #include "system_stm32f2xx.h" /****************************************************************************/ void main(void) { TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; TIM_OCInitTypeDef TIM_OCInitStructure; GPIO_InitTypeDef GPIO_InitStructure; uint16_t period; uint16_t pulse; /* Initialize clock - defined in system_stm32f2xx.h */ SystemInit(); /* Compute the value for the ARR register to have a period of 20 KHz */ period = (SystemCoreClock / 20000 ) - 1; /* Compute the CCR1 value to generate a PWN signal with 50% duty cycle */ pulse = (uint16_t) (((uint32_t) 5 * (period - 1)) / 10); /* GPIOA clock enable */ RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); /* Initialize PA8, Alternative Function, 100Mhz, Output, Push-pull */ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; 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(GPIOA, &GPIO_InitStructure); GPIO_PinAFConfig(GPIOA, GPIO_PinSource8, GPIO_AF_TIM1); /* TIM1 clock enable */ RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1 , ENABLE); /* Timer Base configuration */ TIM_TimeBaseStructInit(&TIM_TimeBaseStructure); TIM_TimeBaseStructure.TIM_Prescaler = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; TIM_TimeBaseStructure.TIM_Period = period; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_RepetitionCounter = 0; TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure); /* Channel 1 output configuration */ TIM_OCStructInit(&TIM_OCInitStructure); TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; TIM_OCInitStructure.TIM_Pulse = pulse; TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set; TIM_OC1Init(TIM1, &TIM_OCInitStructure); /* TIM1 counter enable */ TIM_Cmd(TIM1, ENABLE); /* TIM1 Main Output Enable */ TIM_CtrlPWMOutputs(TIM1, ENABLE); /* forever... */ while (1) { __asm("nop"); } }