STM32F3的ADC使用DMA模式传输转换数据

本文使用ADC转换电位器输出的电压值，并用DMA模式传输转换的结果，每8次采样转换取平均值，做一个简单的数字滤波。

ADC的详细配置与使用

见之前的日记STM32中ADC的使用，只是最后增加一步配置DMA：

DMA for ADC channels features configuration
 To enable the DMA mode for ADC channels group, use the ADC_DMACmd() function.
 To configure the DMA transfer request, use ADC_DMAConfig() function.

DMA的配置

(摘自STM32F3官方用户手册UM1581 User manual)
1. Enable The DMA controller clock using
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE) function for DMA1 or using RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA2, ENABLE) function for DMA2.
2. Enable and configure the peripheral to be connected to the DMA channel (except for internal SRAM / FLASH memories: no initialization is necessary).
3. For a given Channel, program the Source and Destination addresses, the transfer Direction, the Buffer Size, the Peripheral and M