Datasheet

33.6.6 Accumulation
The result from multiple consecutive conversions can be accumulated. The number of samples to be
accumulated is specified by the Number of Samples to be Collected field in the Average Control register
(AVGCTRL.SAMPLENUM). When accumulating more than 16 samples, the result will be too large to
match the 16-bit RESULT register size. To avoid overflow, the result is right shifted automatically to fit
within the available register size. The number of automatic right shifts is specified in the table below.
Note: To perform the accumulation of two or more samples, the Conversion Result Resolution field in
the Control B register (CTRLB.RESSEL) must be set.
Table 33-2. Accumulation
Number of
Accumulated
Samples
AVGCTRL.
SAMPLENUM
Intermediate
Result Precision
Number of
Automatic
Right Shifts
Final Result
Precision
Automatic
Division
Factor
1 0x0 12 bits 0 12 bits 0
2 0x1 13 bits 0 13 bits 0
4 0x2 14 bits 0 14 bits 0
8 0x3 15 bits 0 15 bits 0
16 0x4 16 bits 0 16 bits 0
32 0x5 17 bits 1 16 bits 2
64 0x6 18 bits 2 16 bits 4
128 0x7 19 bits 3 16 bits 8
256 0x8 20 bits 4 16 bits 16
512 0x9 21 bits 5 16 bits 32
1024 0xA 22 bits 6 16 bits 64
Reserved 0xB - 0xF 12 bits 12 bits 0
33.6.7 Averaging
Averaging is a feature that increases the sample accuracy, at the cost of a reduced sampling rate. This
feature is suitable when operating in noisy conditions.
Averaging is done by accumulating m samples, as described in 33.6.6 Accumulation, and dividing the
result by m. The averaged result is available in the RESULT register. The number of samples to be
accumulated is specified by writing to AVGCTRL.SAMPLENUM.
The division is obtained by a combination of the automatic right shift described above, and an additional
right shift that must be specified by writing to the Adjusting Result/Division Coefficient field in AVGCTRL
(AVGCTRL.ADJRES).
Note: To perform the averaging of two or more samples, the Conversion Result Resolution field in the
Control B register (CTRLB.RESSEL) must be set to '1'.
Averaging AVGCTRL.SAMPLENUM samples will reduce the un-averaged sampling rate by a factor
1
AVGCTRL.SAMPLENUM
.
When the averaged result is available, the INTFLAG.RESRDY bit will be set.
SAM D21 Family
ADC – Analog-to-Digital Converter
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 899