Question

我一直在用C ++实现基于CAN的专有通信协议。该协议使用具有以下结构的消息：

1       Control packet  (3 bytes header, 5 payload bytes)
0 - 124 Data packets    (2 bytes header, 6 payload bytes)
1       CRC packet      (2 bytes header, 4 payload bytes, 2 CRC bytes)

我没有太多的通信协议实施经验，所以我我想在这里讨论我的解决方案。我已经开始传输了。

从顶视图我决定划分传输的实现分为三类。他们每个人都将实现Singleton设计模式。类接口如下：

// Main interface for communication over CAN bus.
class Manager
{
  public:

      // initializes the CAN periphery (baud rate and reception filters)
      bool init(can_baudrate_e, uint16_t*);
      // creates the message, divides the message into packets and puts the 
      // packets into transmission queue, message description (type, 
      // destination node ID) and message data are stored in a structure
      bool sendMsg(app_msg_data_t*);


  private:

      // appends unique message code to informations in app_msg_data_t 
      // structure
      void buildMsg(app_msg_data_t*, msg_t*);
      // calculates needed number of packets
      uint8_t calcNoPkts(msg_t*);
      // divides the message into packets
      void appMsg2Pkts(msg_t*, uint8_t, pkt_t*);
      // creates message Control packet
      void buildAppControlPkt(msg_t*, pkt_t*, uint8_t, uint8_t);
      // creates message Data packet
      void buildAppDataPkt(msg_t*, pkt_t*, uint8_t);
      // creates message CRC packet
      void buildAppCRCPkt(msg_t*, pkt_t*, uint8_t, uint8_t);
      // transform whole message into byte array
      uint16_t getAppMsgBytes(pkt_t*, uint8_t, uint8_t*);
      // returns the data content of the message
      uint8_t* getAppMsgData(msg_t*);
      // calculates the CRC for a message (message passed as array of bytes) 
      uint16_t calcCRC(uint8_t*, uint16_t);
} 


// Transmission buffer
class TxQueue
{

   public:
      // puts the packet into the transmission queue
      bool putPacket(Manager::pkt_t*);
      // retrieves the packet from the transmission queue
      bool getPacket(Manager::pkt_t*);

   private:
}

// Transmits the packets onto the CAN bus
class Transmitter
{

    public:
      // transmits one packet per call onto the CAN bus 
      bool transmit(void);

    private:
      // transforms the packet into CAN frame
      static void packet2CANFrame(Manager::pkt_t*, can_msg_t*);

}

如果比我更有经验的人可以评估我的解决方案，我将非常感激。我害怕走错路。提前感谢您的任何建议。

Answer 1

我建议先阅读Guide to Implementing Communication Protocols in C++ (for Embedded Systems)免费电子书。本书中提到的主要概念是，嵌入式系统在未来通过不同的附加I / O接口（例如wifi或蓝牙）尝试使用相同的协议消息并不罕见。因此，将应用程序消息有效负载与传输帧分离，尤其是CAN总线封装分离将是有益的。

嵌入式C ++中的通信协议实现

1 个答案: