I would like, for educational purposes, to read PLC symbols table by using libnodave (or any equivalent open-source like snap7).
Actually, when I read data from merkers, I must know in advance what kind of variable will be present in the DB, also due to the fact that libnodave reads raw bytes in sequences.
I'm searching a way to know in advance what kind of data was chosen by the plc programmer when storing data so, when I use raw bytes read, I can easily monitor variables and adapt my reading and visualization routine.
Thanks in advance.
A program in a S7-3xx/4xx PLC has no symbolic addressing downloaded. So Libnodave or Snap7 can't point to a symbol.
TIA and the S7-12xx/15xx PLC are different. They have symbols downloaded. But so far as i know Libnodave or Snap7 can not use these symbols yet.
A solution maybe is the export the Symboltable is Step7/TIA to an Excel or .scv file and read there the symbol with it's format and address information.
(Libnodave does not support S7-12xx/15xx, use Snap7 instead.)