步骤1：打开串口

SerialPort port = new SerialPort("COM7")
port.BaudRate = 9600;
port.BaudRate = 9600;
port.DataBits = 8;
port.Parity = Parity.Odd;
port.StopBits = StopBits.One;
port.Open();    

                

步骤二：创建ModbusSerialMaster，设置超时参数

var master = ModbusSerialMaster.CreateRtu(port);
master.Transport.ReadTimeout = 2000;
//其中transport还有重试次数和重试间隔时间，默认是3和250
//master.Transport.Retries + "  " + master.Transport.WaitToRetryMilliseconds;

步骤三：设置协议参数，开始读写

 byte slaveID = 3;
ushort address = 1;
bool[] coils = new bool[8];

coils = master.ReadCoils(slaveID, address, 1);

以上面方式读线圈，超时就会抛出异常。