关于STM32串口通信的问题

发布于 2016-04-26 17:20:40 浏览：4105 订阅该版

为什么这个程序每次都读写一个字符，最后却能够完成多字符通讯。如果我想自己编写通讯协议，在which内怎么能够同时判定多字符（which内每次读写一个字符）

```c
#include <rtthread.h>

struct rx_msg 
{ 
  rt_device_t dev; 
  rt_size_t size; 
}; 
/* 用于接收消息的消息队列*/ 
static rt_mq_t rx_mq; 
/* 接收线程的接收缓冲区*/ 
static char uart_rx_buffer[512]; 
static char uart_sx_buffer[512]; 
/* 数据到达回调函数*/ 
rt_err_t uart_input(rt_device_t dev, rt_size_t size) 
{ 
  struct rx_msg msg; 
  msg.dev = dev; 
  msg.size = size; 
 
  /* 发送消息到消息队列中*/ 
  rt_mq_send(rx_mq, &msg, sizeof(struct rx_msg)); 
 
  return RT_EOK; 
} 
 
void device_thread_entry(void* parameter) 
{ 
  struct rx_msg msg; 
  int count = 0; 
  rt_device_t device, write_device; 
  rt_err_t result = RT_EOK; 
 
  /* 查找系统中的串口1设备 */ 
  device = rt_device_find("uart1"); 
  if (device!= RT_NULL) 
  { 
    /* 设置回调函数及打开设备*/ 
    rt_device_set_rx_indicate(device, uart_input); 
    rt_device_open(device, RT_DEVICE_OFLAG_RDWR); 
  } 
  /* 设置写设备为uart1设备 */ 
  write_device = device; 
 
  /* 查找系统中的串口2设备 */ 
  device= rt_device_find("uart2"); 
  if (device != RT_NULL) 
  { 
    /* 设置回调函数及打开设备*/ 
    rt_device_set_rx_indicate(device, uart_input); 
    rt_device_open(device, RT_DEVICE_OFLAG_RDWR); 
  } 
 
  while (1) 
  { 
    /* 从消息队列中读取消息*/ 
    result = rt_mq_recv(rx_mq, &msg,  
      sizeof(struct rx_msg), 50); 
//    if (result == -RT_ETIMEOUT) 
//    { 
//      /* 接收超时*/ 
//      rt_kprintf("timeout count:%d
", ++count); 
//    } 
// 
    /* 成功收到消息*/ 
    if (result == RT_EOK) 
    { 
      rt_uint32_t rx_length; 
      rx_length = (sizeof(uart_rx_buffer) - 1) > 
msg.size ? msg.size : sizeof(uart_rx_buffer) - 1; 
 
      /* 读取消息*/ 
      rx_length = rt_device_read(msg.dev, 0, 
&uart_rx_buffer[0], rx_length); 
      uart_rx_buffer[rx_length] = '�'; 
 
      /* 写到写设备中*/ 
      if (write_device != RT_NULL) 
        rt_device_write(write_device, 0, 
&uart_rx_buffer[0], rx_length); 
    } 
  } 
} 
 
static struct rt_messagequeue s_your_mq;//消息队列控制块对象
static char s_msg_pool[1024];//消息池

int rt_application_init()
{

/* 创建devt线程*/
  rt_thread_t thread = rt_thread_create("devt",
    device_thread_entry, RT_NULL,
    1024, 25, 7); 
	
	  rt_mq_init(&s_your_mq,"test",&s_msg_pool[0],sizeof(struct rx_msg),sizeof(s_msg_pool),RT_IPC_FLAG_FIFO);//初始化消息队列控制块
  rx_mq =&s_your_mq;//将rx_mq再指向s_your_mq
  /* 创建成功则启动线程*/
  if (thread != RT_NULL)
    rt_thread_startup(thread);
}
```