That could be the problem now. I have only updated the master code. The slave code is still the older one! I have to update the slave side too I think, other way it comes only different things. The slave side receives some HEX values that could be possible. On the master side it receives special crc data that I think it is not correct at all. And because the master code is the newest with the changes I have made, and the slave receives the data from the master, it is really possible that is the problem!
I will try to adapt the slave code too and give some report here.
What do you mean with the c-string part? Do you have an example or can show it?