3.1 Global Tools

• ValueHelper.cs

  ValueHeloper is a value translation tooling class, included ValueHelper(Little Endian), BigEndianValueHelper(Big Endian), BigEndianMsbValueHelper(Big Endian with Most Significant Bit).
  ValueHelper(s) are all singleton.

  • ByteLength

    Byte length of a basic type.

  • GetBytes

    Change value type to byte array.

  • ObjectArrayToByteArray

    Change value array to byte array.

  • GetValue

    Change byte array to value type.

  • ByteArrayToObjectArray

  • ByteArrayToDestinationArray

    Change byte array to value array.

  • SetValue

    Set a value to byte array.

  • Instractions of "destination system".

    Almost all functions in ValueHelper contains a param called "ref pos", this is a "pointer" point to the current position of byte array.
    For example, there is a byte array with length 8, now 5th and 6th byte need to be changed to short value.
    Currently pos is 4.

    0x08	0x17	0xa3	0xc4	0x00	0x05	0xa1	0x03
    				pos=4

    Call "ValueHelper.Instance.GetShort" translation function.

    (data == byte[], pos == 4)
    
    short a = ValueHelper.Instance.GetShort(data, ref pos);

    After the translation, pos will be changed to 6 for the next translation.

    0x08	0x17	0xa3	0xc4	0x00	0x05	0xa1	0x03
    						pos=6

  • For getting ValueHelper instance

    ValueHelper has a static function called "GetInstance", it has a param called Endian. That means you can get proper ValueHelper by pass a Endian variable to ValueHelper. This is very useful when you want to make endian changable.

• CRC16.cs

  CRC16 offers CRC16 check/generation and LRC check/generation.

• AsyncHelper.cs

  AsyncHelper contains frequent async operations.

  • RunSync: Run async method syncronize.
  • WithCancellation: Run async method with cancellation token.

  Also Nito.AsyncEx has been included in Modbus.Net.

• AddressHelper.cs

  AddressHelper include some fast sub address translation functions.

  • Introduction of "sub address system"

    Modbus.Net has two coordinations for describing sub address: Absolute Coordinate and Relative Coordinate.
    

    Following passeages will summarize their relationship.

    Data read write protocol(3x, 4x) in Modbus uses word for data unit operation. Word contains 2 bytes, which equals ushort in C#.

    Absolute Coordinate always regards 1 address to 8 bits. Relative Coordinate regards 1 address depends on data unit operation length.
    For instace, Modbus data operation unit always contains 2 bytes, so Relative Coordinate is 16 bits for that.

    Absolute	Relative
    30001 6b	3X 1 6b
    30001 15b	3X 2 7b
    40116 13b	4X 232 5b

    Besides, Switching read write (0x, 1x) use bit for data unit operation.

    So Relative Coordinate is 1 bit for an address.

    Absolute	Relative
    00001 0b	0X 1 0b
    00015 0b	0X 2 7b
    10116 0b	1X 14 3b

    In brief, Relative Coordinate represents byte count for an address in a protocol. But only one byte is mapped to an address in Absolute Address.
    AddressHelper contains the functions that change numbers between relative coordinate and absolute coordinate.