Arduino Zero clock config


How is the clock configurated in the Arduino Zero. Like this?

I want to start using the Atmel Start in Atmel Studio, So I have to know how the Zero is properly configurated :slight_smile:


I got it working using this connection:


You have to make sure that you enable the xtal and the 32kHz output

Maybe you can even disable the 8Mhz oscillator. If you want to use the crystal in sleep modes you have to tick the according boxes.

I have the same problem,
but unfortunately the links posted by @tsaG are down ...

How is the correct "Atmel Start" clock configuration for the Arduinio Zero ?

Hi Dirk,

I don't have a good picture, but the following is the clock setup from the samd21_sam_ba bootloader (I think this part is the same for Arduino Zero's and Adafruit Feather's):


  • \brief system_init() configures the needed clocks and according Flash Read Wait States.
  • At reset:
    • OSC8M clock source is enabled with a divider by 8 (1MHz).
    • Generic Clock Generator 0 (GCLKMAIN) is using OSC8M as source.
  • We need to:
    1. Enable XOSC32K clock (External on-board 32.768Hz oscillator), will be used as DFLL48M reference.
    1. Put XOSC32K as source of Generic Clock Generator 1
    1. Put Generic Clock Generator 1 as source for Generic Clock Multiplexer 0 (DFLL48M reference)
    1. Enable DFLL48M clock
    1. Switch Generic Clock Generator 0 to DFLL48M. CPU will run at 48MHz.
    1. Modify PRESCaler value of OSCM to have 8MHz
    1. Put OSC8M as source for Generic Clock Generator 3

correct "Atmel Start" clock configuration for the Arduinio Zero ?

What does "correct" mean here? The Zero has a 32.768kHz crystal, and the Arduino Core and libraries all assume 48MHz core clock. But if you're not using the Arduino code, you should be able to set up the clock any way you want.