STM32F051C8T6驱使一个灯的慢慢变亮再变暗

            我想用这个芯片来使一个灯慢慢的变亮，之后又慢慢的变暗。
但是我的写的程序，灯亮着，但是一直没有变化，希望大家能帮我找一下原因。
谢谢
下面是我的主程序，还有timer.c程序。
#include "timer.h"
#include "STM32f0xx.h"
#include "sys.h"

void TIM16_PWM_Init(uint16_t arr,uint16_t psc)
{
GPIO_InitTypeDef  GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseInitStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM16,ENABLE);//使能定时器16时钟
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB,ENABLE);

GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType=GPIO_OType_PP;
GPIO_InitStructure.GPIO_Pin=GPIO_Pin_8;
GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_Level_2;
GPIO_Init(GPIOB,&GPIO_InitStructure);


GPIO_PinAFConfig(GPIOB,GPIO_PinSource8,GPIO_AF_2);//映射外设端口

//初始化定时器

TIM_TimeBaseInitStructure.TIM_ClockDivision=0;
TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInitStructure.TIM_Period=arr;
TIM_TimeBaseInitStructure.TIM_Prescaler=psc;
TIM_TimeBaseInit(TIM16,&TIM_TimeBaseInitStructure);

TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable;
TIM_OC1Init(TIM16,&TIM_OCInitStructure);

TIM_OC1PreloadConfig(TIM16,TIM_OCPreload_Enable);

TIM_Cmd(TIM16,ENABLE);
}


#include "stm32f0xx.h"
#include "timer.h"
void  Delay (uint32_t nCount);
int main(void)
{
uint16_t ledpwmval=0;
uint8_t dir=1;
SystemInit();
SysTick_Config(3000);
SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8);
TIM16_PWM_Init(299,0);
while(1)
{
  //Delay(10);
  if(dir)
   ledpwmval++;
  else
   ledpwmval--;
  if(ledpwmval>100)dir=0;
  if(ledpwmval==0)dir=1;
  TIM_SetCompare1(TIM16,ledpwmval);
  }
}
void  Delay (uint32_t nCount)
{
  for(; nCount != 0; nCount--);
}