F407 中printf 的实现

装载  自  http://bbs.21ic.com/icview-860453-1-1.html

配置串口，利用printf函数输出字符，结果输出的还是ASCII码，这是为什么？难道是我的配置问题？
串口配置是没有问题的，那个printf的配置是在网上找的资料，就不清楚了。。

1. #include "stm32f4xx.h"
2. #include <stdio.h>
5. void OpenCom(void)
6. {
7.   USART_InitTypeDef USART_InitStructure;
8.   NVIC_InitTypeDef NVIC_InitStructure; 
9.   GPIO_InitTypeDef GPIO_InitStructure;
11.   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);        
12.   RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
14.   GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1);        
15.   GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);
17.   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_10;
18.   GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
19.   GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
20.   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
21.   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
22.   GPIO_Init(GPIOA, &GPIO_InitStructure);
24.   USART_InitStructure.USART_BaudRate = BaudRate;
25.   USART_InitStructure.USART_WordLength = USART_WordLength_8b;
26.   USART_InitStructure.USART_StopBits = USART_StopBits_1;
27.   USART_InitStructure.USART_Parity = USART_Parity_No;
28.   USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
29.   USART_InitStructure.USART_Mode = USART_Mode_Rx|USART_Mode_Tx;
31.   USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);
32.   USART_Init(USART1, &USART_InitStructure);        /* USART configuration */
33.   USART_Cmd(USART1, ENABLE); /* Enable USART */
34.   USART_ClearFlag(USART1, USART_FLAG_TC);
36.   NVIC_InitStructure.NVIC_IRQChannel=USART1_IRQn;
37.   NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0;
38.   NVIC_InitStructure.NVIC_IRQChannelSubPriority=0;
39.   NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
40.   NVIC_Init(&NVIC_InitStructure);  
41. }
43. int main(void)
44. {  
46.    unsigned char i='a';     
47.    OpenCom();
48.    printf("%c\r\n",i);
49.             
50. }
52. int fputc(int ch,FILE *f)
53. {
54.   USART_SendData(USART1,(unsigned char)ch);
55.   while(!(USART1->SR&USART_FLAG_TXE));
56.   return (ch);
57. }

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