Hi Fernando,
sorry if I'm writing again, I do some research but I couldn't find any answer.
Everything now works fine expect the DS1307, I have the iTead lcd shield with the rtc on board, I've tested the connection (on pin 20,21)with your examples and I can find the RTC with 0x68 address and I can read time and date.
When I upload Ferduino, with PCF8575 disabled, I can't connect to the rtc (I already tried switch betwenn 20,21 and 18,19 pin with thw option at the beginning).
What can I try to do? thank you very much again!