An accumulator in the ADC can be used to average noise on the analog input. In general, oversampling improves the signal-to-noise ratio (SNR). Oversampling, however, does not improve the integral non-linearity (INL), or differential non-linearity (DNL).
Oversampling and Scan mode should not be combined, since oversampling and scan will average over input channels.
The accumulator is controlled in the OVERSAMPLE register. The SAMPLE task must be set 2OVERSAMPLE number of times before the result is written to RAM. This can be achieved by the following:
- Configuring a fixed sampling rate using the local timer or a general purpose timer and the PPI system to trigger a SAMPLE task
- Triggering SAMPLE 2OVERSAMPLE times from software
- Enabling BURST mode
CH[n].CONFIG.BURST can be enabled to avoid setting SAMPLE task 2OVERSAMPLE times. With BURST = 1 the ADC will sample the input 2OVERSAMPLE times as fast as it can (actual timing: <(tACQ+tCONV)×2OVERSAMPLE). Thus, for the user it will just appear like the conversion took a bit longer time, but other than that, it is similar to One-shot mode.
A DONE event signals that one sample has been taken.
In this mode, the RESULTDONE event signals that enough conversions have taken place for an oversampled result to get transferred into RAM. Both events may occur before the actual value has been transferred into RAM by EasyDMA.