Continuous mode

Continuous sampling can be achieved by using the internal timer in the ADC, or triggering the SAMPLE task from one of the general purpose timers through the PPI system.

Care shall be taken to ensure that the sample rate fulfils the following criteria, depending on how many channels are active:

t_SAMPLE> t_ACQ + t_CONV

If t_ACQ=0 and t_CONV=0, SAADC will use pipelining to increase sampling speed. In this case, the time for the first sample to arrive is

t_{SAMPLE =}t_PWRUP + t_ACQ + t_CONV

and for subsequent samples

f_SAMPLE = 1/(t_CONV)

The SAMPLERATE register can be used as a local timer instead of triggering individual SAMPLE tasks. When SAMPLERATE.MODE is set to Timers, it is sufficient to trigger SAMPLE task only once in order to start the SAADC and triggering the STOP task will stop sampling. The SAMPLERATE.CC field controls the sample rate.

A DONE event signals that one sample has been taken.

In this mode, the RESULTDONE event has the same meaning as DONE when no oversampling takes place. Note that both events may occur before the actual value has been transferred into RAM by EasyDMA.