ModbusRTU协议

在网上找了很久都没找的Stm32 有关Modbus协议的代码，所以根据modbus的协议文档自己写了一个，可以使用。逻辑并不复杂很简单

主文件：stm32.ino

#define BAUD 9600

char pin[27] = {PA0,PA1,PA2,PA3,PA4,PA5,PA6,PA7,PA8,PA11,PA12,PA15,PB0,PB1,PB2,PB3,PB4,PB5,PB6,PB7,PB8,PB9,PB10,PB11,PB12,PB13,PB15};

void setup() {
    for(int i=0;i < 26;i++){
      pinMode(pin[i], OUTPUT);
  }
  
  Serial.begin(BAUD);  // BAUD has no effect on USB serial: placeholder for physical UAR
    // wait for serial monitor to be connected.
  while (!Serial)
  {
    digitalWrite(33,!digitalRead(33));// Turn the LED from off to on, or on to off
    delay(100);         // fast blink
  }
  Serial.println("Serial Read Until Example:");
  Serial.print("Type a few characters & press ENTER\r\n(make certain serial monitor sends CR+LF)");
}

void loop() {
    mloop();
    updatePin();
}

// 读取保持寄存器并设置对应引脚
void updatePin(){
   char *holdingRegister = getHoldingRegister({0x00});
   char high1 = holdingRegister[0];
   for(int i=0;i < 8;i++){
      int dp = high1 >> i & 0x01;
      digitalWrite(pin[i],dp != 0 ? LOW : HIGH);
   }

   char low1 = holdingRegister[1];
   for(int i=8;i < 27;i++){
      int dp = high1 >> i & 0x01;
      digitalWrite(pin[i],dp != 0 ? LOW : HIGH);
   }
}

modbus实现逻辑：modbus.ino

#define MODBUSADDRESS 0x02

enum FUN {
   // 读取保持寄存器
   READE_HOLD = 0x03,
   // 写多个保持寄存器
   WRITE_MULTIPLE_HOLD = 0x10
};

char serialdata[32];
int  idx = -1;
int  lastreadtime = 0;
// 保持寄存器
char holdingRegister[16][64];
char result[32];

// 读串口数据
void mloop(){
     if (Serial.available() > 0){
           serialdata[++idx] = Serial.read();
           lastreadtime = millis();
    }else if(lastreadtime != 0 && millis() - lastreadtime > (1.04 * 3.5)){
          int requestLen = analysisdata();
          if (requestLen != NULL){
              Serial.write(result,requestLen);
          }
          idx = -1;
          lastreadtime = 0;
    }
}

// 获取保持寄存器
char *getHoldingRegister(char address){
  return holdingRegister[address];
}

int analysisdata(){
   int address = serialdata[0];
   if(MODBUSADDRESS != address){
       return NULL;
   }

   if(!checkCrc()){
       return NULL;
   }

   char fun = serialdata[1];
   char data[1024];
   char dlen = 0;
   switch(fun){
       case READE_HOLD:
          dlen = readHoldingRegister(data);
          break;
       case WRITE_MULTIPLE_HOLD:
          dlen = writeHoldingRegister(data);
          break;
       default:
          return NULL;
   }

   int len = 3 + dlen + 2;

   result[0] = MODBUSADDRESS;
   result[1] = fun;
   result[2] = dlen;

   for(int i= 0;i < dlen;i++){
      result[i+3] = data[i];
   }
   
   uint16_t crc = generateCrc(result,len - 2);
   result[len - 1] = crc >> 8;
   result[len - 2] = crc & 0x00ff;

   return len;
}

// 检查CRC
bool checkCrc(){
  int dlen = idx - 1;
  char data[dlen]; 
  memcpy(data,serialdata,dlen);
  
  uint16_t crc = generateCrc(data,dlen);
  return serialdata[idx - 1] == (crc & 0x00ff) && serialdata[idx] == (crc >> 8);
}

// 冗余计算CRC
uint16_t generateCrc(char *data,int dlen){
    uint16_t crcData = 0xffff;
    for(int i = 0;i < dlen;i++){       
       crcData = oneByteCrc(data[i],crcData);
    }
    return crcData;
}

// 计算CRC 
uint16_t oneByteCrc(char data,uint16_t crcData){
  uint16_t crcDataTmp1 = ((crcData & 0x00ff) ^ data) + (0xff00 & crcData);
  int len = 8;
  while((len--) != 0){
      if ((crcDataTmp1 & 0x0001) == 0){
         crcDataTmp1 = crcDataTmp1 >> 1;
      }else{
        crcDataTmp1 = ((crcDataTmp1 >> 1) ^ 0xA001);
      }
  }
  return crcDataTmp1;
}



void getAddressAndRegisterNum(char *data,char *val){
    // 寄存器起始位置
  char high = serialdata[2];
  char low = serialdata[3];
  int address = high+low;
  val[0] = address;
  
  // 读寄存器个数
  char highNum = serialdata[4];
  char lowNum = serialdata[5];
  int len = high+lowNum;
  val[1] = len;
}

// 返回读取保持寄存器的字节数
int readHoldingRegister(char *data){  
  char val[2]; 
  getAddressAndRegisterNum(serialdata,val);
  int address = val[0];
  int len = val[1];

  char *holdData = holdingRegister[address]; 
  int hold = len * 2; 
  for(int i= 0, j = 0;i < hold;i++){
      data[i] = holdData[i];
  }
  reverse(data,hold);
  return hold;
}

// 返回读取保持寄存器的字节数
int writeHoldingRegister(char *data){
  char val[2]; 
  getAddressAndRegisterNum(serialdata,val);
  
  int address = val[0];
  int len = val[1];
  int byteLen = serialdata[6];

  char bytes[byteLen];
  char *holdData = holdingRegister[address];
  for (int i= 0,j= 7 + byteLen -1;i < byteLen;i++,j--){
    holdData[i] = serialdata[j];
  }

  data[0] = {0x00};
  data[1] = {0x01};
  
  data[2] = serialdata[4];
  data[3] = serialdata[5];
  return 4;
}

// 反转数组
void reverse(char *data,int len){
    char i,n = len,temp;
    for(i= 0;i < len / 2;i++){
        temp= data[i];
        data[i]= data[n-1-i];
        data[n-1-i]= temp;
    }  
}