Continuous mode

Continuous sampling is 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.

The sample rate must meet the following criteria, depending on how many channels are active:

t_SAMPLE> t_ACQ + t_CONV

SAADC will use pipelining to increase sampling speed when the following are true:

tACQ=0
tCONV=0

In this case, the time for the first sample to arrive is given by the following equation:

t_SAMPLE=t_PWRUP + t_ACQ + t_CONV

Subsequent samples are given by the following equation:

f_SAMPLE=1/(t_CONV)

The register SAMPLERATE 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 peripheral. 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. Both events may occur before the value has been transferred into RAM by EasyDMA.