c - UART ISR Tx Rx 架构

Question

我是不是把事情复杂化了？

我正在设计我的代码以通过 UART 从 8051 微型计算机与外围设备通信。外设响应主机的命令，一次只能响应一个命令。这是一个简单的发送和接收协议(protocol)。 (tx1, rx1, tx2, rx2, tx3, rx3) 每个 TX 消息以 CR 结束，每个响应以 > 结束。在收到对上一条消息的回复之前，我无法发送新消息。如果我启用该选项，响应也可以在开始时回显打印原始 TX 消息(但这会导致更多流量)

示例消息是:

• TX:你好
• RX:世界!>

或者使用 echo 选项...

• TX:你好
• RX:你好\rWorld!>

选项 A 诸如 getHello 之类的函数将包含发送和接收。并行 ISR 例程将收集传入字节并在收到“>”字符时抛出一个标志。

char* getHello(char * buf){
    sendMsg("Hello\r");
    delay(10ms); //wait a little bit

    //wait for receive to come in or timeout to occur
    while(!receiveFlag || !timeoutFlag);  //thrown by ISR
    receiveMsg(buf);
    //parse the message and do some other stuff
    return buf;
}

优点:

• 一切都包含在一个函数中。
• 更容易调试

缺点:

• 此函数是阻塞的，如果外设从不响应则可能会挂起，因此必须实现超时。
• 消息不能乱序接收，必须是连续的(即tx1, rx1, tx2, rx2, tx3, rx3)

选项 B 采用并行方法。将创建两个单独的函数。一个用于发送消息，一个在收到 ISR 的响应后会转向。

void sendHello(){
    sendMsg("Hello\r");
    //do some other stuff if needed
}

char* receiveMsg(char * buf){
    //figure out from echo print what the tx message was
    //use a switch statement to decide which response parser to call
    switch(txMessage){ //pseudo code
    case "Hello":
        receiveMsg(buf);
        //parse the message and do some other stuff
        break;
    }
    return buf;
}

优点:

• 可以处理乱序返回的并行消息，因为它依赖于 tx 消息的回显打印来确定如何解析它。 (即 tx1、tx2、tx3、rx1、rx2、rx3)

缺点:

• 很难调试
• 产生多个线程
• 大量额外代码
• 不值得，因为消息肯定会按顺序返回

---

现在，我正在做选项 B，但随着我继续这个项目，我开始觉得这变得过于复杂了。我很好奇你们的想法。

谢谢!

Answer 1

不过，我倾向于做这类事情，我倾向于有一个单独的串行端口“类”(结构 + 函数)和一个位于串行端口之上的协议(protocol)类。我一直在我的嵌入式系统中使用这些。这为您提供了两全其美的方法，一个阻塞的同步调用和一个异步调用，这样您就可以进行伪多任务处理。

typedef struct serial_port_s serial_port;
typedef void (*serial_on_recived_proc)(serial_port* p);
typedef struct serial_port_s{
    bool timeoutFlag;
    bool receiveFlag;
    void* context;
    serial_on_recived_proc response_handler;
};

void send_serial(serial_port* p, char* message)
{
    //SendMsg?
}
void receive_serial(serial_port* p, char* response)
{
    //receiveMsg?
}

bool has_data(serial_port* p)
{
    return p->receiveFlag;
}

bool has_timed_out(serial_port* p)
{
    return p->timeoutFlag;
}
bool is_serial_finished(serial_port* p)
{
    return has_data(p) || has_timed_out(p); 
}

bool serial_check(serial_port* p)
{
    if(is_serial_finished(p) && p->response_handler != NULL)
    {
       p->response_handler(p)
       p-> response_handler = NULL;
       return true;
    }
    return false;
}

void send(serial_port* p, char* message, char* response)
{
    p->response_handler=NULL;
    send_serial(p, message);
    while(!is_serial_finished(p));
    receive_serial(p, response);
}

void sendAsync(serial_port* p, char* message, serial_on_recived_proc handler, void* context)
{
    p->response_handler = handler;
    p->context = context;
    send_serial(p, message);
}

void pow_response(serial_port* p)
{
    // could pass a pointer to a struct, or anything depending on what you want to do
    char* r = (char*)p->context;  
    receive_serial(p, r);
    // do stuff with the pow response
}

typedef struct
{
   char text[100];       
   int x;
   bool has_result;
} bang_t;

void bang_parse(bang_t* bang)
{
   bang->x = atoi(bang->text);
}

void bang_response(serial_port* p)
{
    bang_t* bang = (bang_t*)p->context;  
    receive_serial(p, bang->text);
    bang_parse(bang);
    bang->has_result=true;
}

void myFunc();
{
    char response[100];
    char pow[100];
    bang_t bang1;
    bang_t bang2;
    serial_port p; //
    int state = 1;
    // whatever you need to do to set the serial port

    // sends and blocks till a response/timeout
    send(&p, "Hello", response);
    // do what you like with the response

    // alternately, lets do an async send...
    sendAsync(&p, "Pow", pow_response, pow);       

    while(true)
    {
        // non block check, will process the response when it arrives               
        if(serial_check(p))
            {
              // it has responded to something, we can send something else...

              // using a very simple state machine, work out what to send next.
              // in practice I'd use enum for states, and functions for managing state
              // transitions, but for this example I'm just using an int which
              // I just increment to move to the next state
              switch(state)
              {
              case 1: 
                 // bang1 is the context, and will receive the data
                 sendAsync(&p, "Bang1", bang_response, &bang1);
                 state++; 
                 break;
              case 2:
                 // now bang2 is the context and will get the data...
                 sendAsync(&p, "Bang2", bang_response, &bang2);
                 state++; 
                 break;
              default:
                 //nothing more to send....
                 break;
              }
            }
        // do other stuff you want to do in parallel
    }
};