Does anybody know some docs or exemples about how to use the libsam functions (for dummies) ? Tks
You want to use arduino due -> go to tool->board->board manager. search for DUE.
Then install latest due package.
tthen on board again, select arduino DUE native or programing port (ddepending on witch usb port you connect your DUE)
Thanks nitrof, but the question is about examples infos and docs about the available functions on that libsam and the correct way to invoke them...
It is the core to use the board. After install it, you use it like other arduino, for the specific DUE capabilité, most of them are on 3th party lib, you could take a look on the ressouces->reference tab here in for the library that DUE support like audio and scheduler.
Also un the forum, look to the DUE forum, there's post with users liraries.
Most of them have examples.
For the rest, there's still the sam3x data sheet...
What do you intend to do exactly??
I've deleted your other cross-post @AntonioTesta.
Cross-posting is against the rules of the forum. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend 15 minutes (or more) writing a detailed answer on this topic, without knowing that someone else already did the same in the other topic.
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Thanks in advance for your cooperation.
Does anybody know some docs or exemples about how to use the libsam functions (for dummies) ?
libsam was Atmel's library for their ARM chips, back before they wrote ASF.
As far as I know (and I've asked and looked), there is no documentation for libsam, other than the source code. The Source code does have Doxygen-style comments, I've attached a zip of the Doxygen-generate html, for what it's worth. (Don't get me started.)
the Source code is at ArduinoCore-sam/system/libsam/source at master · arduino/ArduinoCore-sam · GitHub
If you want to do things below the Arduino level, I'd recommend going Bare Metal based on the datasheet rather than trying to deal with libsam 
LibSam-html.zip (344 KB)
And bear in mind its a complicated chip, very much more complex than the ATmega microcontrollers with probably around a thousand control registers (well it feels like it!).
(and one of the problems is that libsam doesn't really help with the complexity any. Instead of setting obscure peripheral registers to obscure values, you have to call obscure functions with obscure arguments... All too many vendor libraries are like this.)
Train yourself with a first peripheral to understand the logical organization of registers. Good news: You will discover that there are lots of similarities in the way all peripherals are setup and used and along the way you will learn a lot on this uc (and all the Sam4/Sam7 uc family...).