NModbus4的使用

步驟1：打開串口

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

                

步驟二：創建ModbusSerialMaster，設置超時參數

var master = ModbusSerialMaster.CreateRtu(port);
master.Transport.ReadTimeout = 2000;
//其中transport還有重試次數和重試間隔時間，默認是3和250
//master.Transport.Retries + "  " + master.Transport.WaitToRetryMilliseconds;

步驟三：設置協議參數，開始讀寫

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

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

以上面方式讀線圈，超時就會拋出異常。

可選步驟四：以async await方式讀寫

比如點擊按鈕之后，調用AcquireStatus 方法

        private async void AcquireStatus(ModbusSerialMaster master)
        {
            byte slaveID = 3;

            ushort address = 1;
            bool[] coils=null;
            master.Transport.ReadTimeout = 2000;
            try {coils=await master.ReadCoilsAsync(slaveID, address, 1); }
            catch (Exception ex)
            {
                MessageBox.Show("your value " + "無返回值");
            }
            
            if (coils != null)
            {
                this.checkBox1.Checked = coils[0];
                MessageBox.Show("your value " + coils[0]);
            }

        }