#STM32F103 DMA方式GPIO输出
使用TIM4 定时器 UP 触发DMA1 通道7，DMA读取内存数据输出到GPIOC。TIM_TimeBaseStructure.TIM_Period = 72; 可以改变输出速度。

/* Private functions ---------------------------------------------------------*/
//通用定时器4初始化
void TIM4_Int_Init(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

/* TIMx clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

TIM_TimeBaseStructure.TIM_Period = 72;
TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
TIM_TimeBaseStructure.TIM_ClockDivision = 0x00;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

TIM_DMACmd(TIM4, TIM_DMA_Update, ENABLE);
TIM_SelectOutputTrigger(TIM4,TIM_TRGOSource_Update);
// TIM_SelectCCDMA(TIM4,ENABLE);
TIM_Cmd(TIM4, ENABLE);

}
//***************************************************
void DMA_INI(void)
{
DMA_InitTypeDef DMA_InitStructure;
/* Enable DMA clock */
RCC_AHBPeriphClockCmd( RCC_AHBPeriph_DMA1, ENABLE );

DMA_DeInit(DMA1_Channel7); 
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&(GPIOC->ODR));  
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)DisBuf;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;  
DMA_InitStructure.DMA_BufferSize = 512;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;  //非内存到内存，否则会不受TIM4 UP 触发
DMA_Init(DMA1_Channel7, &DMA_InitStructure);
DMA1_Channel7->CCR |= DMA_CCR7_EN;	  

}