Hi, i'm new in this world of arduino and in this place with other developers in arduino, well i'm a developer software student and i have to do an aplicaction in arduino, this consist in generate a sine wave form, this starts in 7Hz until 14KHz, so the program begins in 7Hz and will be increase until 14KHz in the time.
how do i do?
There are 2 methods to output a frequency variable sin wave with a DUE:
1/ The PWM synchro feature with an automatic update of duty cycle by the PDC DMA with only PWM channel 0. Update the output frequency in loop() with PWM_CPRDUPD. Use an RC filter to output a sin wave from a PWM.
There is an example sketch here (reply #6) with 3 PWM channels.
2/ A DAC output (no need for an RC filter, but some hardware if you want the full range 0V - 3.3V) with a PDC DMA to output a sin wave buffer, triggered by a PWM event line. Update the output frequency with PWM_CPRDUPD in loop().
There is an example sketch with a PWM event line to trigger ADC conversions here (reply #9). There is an example sketch with DAC conversions and PDC DMA here ( reply #10).
For a full range DAC:
I´m still having the same problem 
everytime when i change something in the code this leaves to work correctly i realy need help, i dont understand the code of everything
I mean that what I want to get is that the arduino of a signal in the arduino sinusoidal, which I already achieve with the previous code but what I want is for me to give a signal of 22 KHz for example, and after 10 seconds change to a 23KHz and after another 10 seconds change to a 24KHz ....
If they helped me to understand the code or know what I would like to modify, I would greatly appreciate it, since I do not understand the code that I found, and this code is the one that has served me the most since it can generate up to 200KHz ....
Please, do not PM me.
If you don't understand the example sketches, begin by the beginning:
1/Output something to DAC0 with analogWrite() and measure with a voltmetre. Don't forget to hook at least a 2KOhms resistor in serie with DAC0 to avoid burning your DAC.
2/Read something from Serial with the basic example sketches given in File>Example>Communication>SerialEvent , etc... up to the point where you understand how that works
3/Mix a DAC0 output with a command received from Serial
4/Open Sam3x datasheet and read the DAC section
5/ ....
Thank you... 