Type–length–value in Codesys

2022-01-02T18:50:08.259000Z

This is pretty much the format that most, if not all, industrial control protocols (e.g. EtherNet/IP, S7, SLMP) follow. Some header that specifies command type and length of the message and is followed by the message data itself. The best way to handle this would be to create a byte array, then use sysmem.cpy and copy the bytes into such array to be sent other some medium (e.g. Ethernet).

For example:
1. Create a byte array called `_abOutput : ARRAY [1..4096] OF BYTE;`
2. Create a STRUCT called `_stMyData` with some variables such as:
    1.  `uiType : UINT;`
    2. `uiLen : UINT;`
    3. `sData : STRING;`
3. Fill out your STRUCT (e.g. uiType := 1, sData := 'hello world', uiLen := len(sData))
4. Then use SysMemCpy to copy into your buffer via something like this `SysMemCpy(pDest:=ADR(_abOutput), pSrc:=ADR(_stMyData), udiCount:=(_stMyData.uiLen+2));`.  The `+2` accounts for the data type size of uiType.

Anyway, then have TCP write client send this out. As the receive part, just do the same thing. Create a struct and copy from the receive buffer back into a STRUCT for "easy" parsing.

Type–length–value in Codesys

2021-12-24T11:38:01.207000Z

Hi,

Personally I never came across such a library. But that said, reading https://en.m.wikipedia.org/wiki/Type%E2%80%93length%E2%80%93value at first glance it seems not too difficult to implement an encoder/decoder.

good luck and merry Christmas 🎄⛄

Type–length–value in Codesys

2021-12-23T06:48:21.095000Z

Hi,
Someone have use Type–length–value coding in Codesys ? I need function to decode data from string. Someone heard about similar solution?

Recent posts to Type–length–value in Codesys

Type–length–value in Codesys

Type–length–value in Codesys

Type–length–value in Codesys