Hello again,
At the end I manage to make it work.
After hours and hours trying numerous setting and code changes, I realised that although the program sent the correct information through the UART1, it didn´t work properly because it was stopped at a reset:
GPIOModuleReset(GPIO_INSTANCE_ADDRESS);
I inserted that code because I want to see the led blinking every time it transmitted something. I downloaded another code for the gpio example (led blinking) from github.com and finally it worked OK. It could be because joining 2 programs (gpio+uart0)of that version of starterware (AM335X_StarterWare_02_00_00_07) in the same program crashed...
Anyway thank you for your help. :)
Regards,