Value conversion

Value conversion between C# and S7 plc

• Read S7 Word:

ushort result = (ushort)plc.Read("DB1.DBW0");

• Write S7 Word:

ushort val = 40000;
plc.Write("DB1.DBW0", val);

• Read S7 Int / Dec, you need to use the method ConvertToShort():

short result = ((ushort)plc.Read("DB1.DBW0")).ConvertToShort();

• Write S7 Int / Dec, you need to use the method ConvertToUshort():

short value = -100;
plc.Write("DB1.DBW0", value.ConvertToUshort());

• Read S7 DWord:

uint result = (uint)plc.Read("DB1.DBD40");

• Write S7 DWord:

uint val = 1000;
plc.Write("DB1.DBD40", val);

• Read S7 Dint, you need to use ConvertToInt():

int result2 = ((uint)plc.Read("DB1.DBD60")).ConvertToInt();

• Write S7 Dint:

int value = -60000;
plc.Write("DB1.DBD60", value);

• Read S7 Real, you need to use ConvertToFloat():

double result = ((uint)plc.Read("DB1.DBD40")).ConvertToFloat();

• Write S7 Real, you need to use ConvertToUInt():

double val = 35.687;
plc.Write("DB1.DBD40", val.ConvertToUInt());

• Read S7 String

// reads a string from DataBlock 156 at address 0 with a length of 50 characters
var tempString = plc.Read(DataType.DataBlock, 156, 0, VarType.StringEx, 50, 0);      
myString = tempString.ToString();

• Write S7 String, you should convert into a bytearray first

// helper function to convert String into ByteArray
private byte[] ConvertStringToByteArray(string myString)
        {
            // convert myString into ByteArray
            // for S7-String-Format:
            // 1. Byte = maximum length of the String
            // 2. Byte = actual length of the String         
   
            int maximumLength = 50; // <-- according to the length of your S7-String, here STRING[50]
            int actualLength = myString.Length;
            byte[] string = System.Text.Encoding.Default.GetBytes(myString);
            byte[] bytearray = new byte[actualLength + 2];

            bytearray[0] = Convert.ToByte(maximumLength);
            bytearray[1] = Convert.ToByte(actualLenght);

            // copy string-array into bytearray, begin at 3. byte 
            for (int i = 2; i < bytearray.Length; i++)
            {
                bytearray[i] = string[i - 2];
            }

            return bytearray;
        }

// use the helper function to convert myString into S7-String and write it to the plc
// write the string into DataBlock 204, startAddress 0
byte[] byteArray = ConvertStringToByteArray(myString);
plc.WriteBytes(DataType.DataBlock, 204, 0, byteArray);

• Read Bool/Bit from byte

// reads 1 byte from DataBlock 153 at address 0
myByte = plc.ReadBytes(DataType.DataBlock, 153, 0, 1); // myByte = 5 = 0000 0101
myByte.SelectBit(0)  // true
myByte.SelectBit(1)  // false

• Write bool/bit from byte

// writes FALSE to DataBlock 157, startAddress 0, bitAddress 0
plc.WriteBit(DataType.DataBlock, 157, 0, 0, false);