Datasheet
839
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181C–SAM-D21_Datasheet–07/2014
32.6.6 Accumulation
The result from multiple consecutive conversions can be accumulated. The number of samples to be accumulated is
specified by writing to the Number of Samples to be Collected field in the Average Control register
(AVGCTRL.SAMPLENUM) as described in Table 32-2. When accumulating more than 16 samples, the result will be too
large for the 16-bit RESULT register. To avoid overflow, the result is shifted right automatically to fit within the 16
available bits. The number of automatic right shifts are specified in Table 32-2. Note that to be able to perform the
accumulation of two or more samples, the Conversion Result Resolution field in the Control B register (CTRLB.RESSEL)
must be written to one.
Table 32-2. Accumulation
32.6.7 Averaging
Averaging is a feature that increases the sample accuracy, though at the cost of reduced sample rate. This feature is
suitable when operating in noisy conditions. Averaging is done by accumulating m samples, as described in
“Accumulation” on page 839, and divide 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 as described in Table 32-3.
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) as
described in Table 32-3. Note that to be able to perform the averaging of two or more samples, the Conversion Result
Resolution field in the Control B register (CTRLB.RESSEL) must be written to one.
Averaging AVGCTRL.SAMPLENUM samples will reduce the effective sample rate by .
When the required average is reached, the INTFLAG.RESRDY bit is set.
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
1
AVGCTRL.SAMPLENUM
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