NRF52820-QDAA-R datasheet(150/437 Pages) NORDIC

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Peripherals

be suppressed by the filter. It is assumed that the frequency during the debounce period never exceeds

500 kHz (as required by the Nyquist theorem when using a 1 MHz sample frequency).

The LED will always be ON when the debounce filters are enabled, as the inputs in this case will be

sampled continuously.

When the debounce filters are enabled, displacements reported by the QDEC peripheral are delayed by

one SAMPLEPER period.

6.11.4 Accumulators

The quadrature decoder contains two accumulator registers, ACC and ACCDBL. These registers accumulate

valid motion sample values and the number of detected invalid samples (double transitions), respectively.

The ACC register will accumulate all valid values (1/-1) written to the SAMPLE register. This can be useful

for preventing hard real-time requirements from being enforced on the application. When using the ACC

ACC register holds the relative movement of the external mechanical device from the previous clearing

of the ACC register. Sample values indicating a double transition (2) will not be accumulated in the ACC

An ACCOF event will be generated if the ACC receives a SAMPLE value that would cause the register

to overflow or underflow. Any SAMPLE value that would cause an ACC overflow or underflow will be

discarded, but any samples not causing the ACC to overflow or underflow will still be accepted.

The accumulator ACCDBL accumulates the number of detected double transitions since the previous

clearing of the ACCDBL register.

The ACC and ACCDBL registers can be cleared by the READCLRACC and subsequently read using the

ACCREAD and ACCDBLREAD registers.

The ACC register can be separately cleared by the RDCLRACC and subsequently read using the ACCREAD

registers.

The ACCDBL register can be separately cleared by the RDCLRDBL and subsequently read using the

ACCDBLREAD registers.

The REPORTPER register allows automated capture of multiple samples before sending an event. When

a non-null displacement is captured and accumulated, a REPORTRDY event is sent. When one or more

double-displacements are captured and accumulated, a DBLRDY event is sent. The REPORTPER field in this

REPORTRDY or DBLRDY event is sent.

Using the RDCLRACC task (manually sent upon receiving the event, or using the DBLRDY_RDCLRACC

shortcut), ACCREAD can then be read.

When a double transition has been captured and accumulated, a DBLRDY event is sent. Using the

RDCLRDBL task (manually sent upon receiving the event, or using the DBLRDY_RDCLRDBL shortcut),

ACCDBLREAD can then be read.

6.11.5 Output/input pins

The QDEC uses a three-pin interface to the off-chip quadrature encoder.

These pins will be acquired when the QDEC is enabled in the ENABLE register. The pins acquired by the

QDEC cannot be written by the CPU, but they can still be read by the CPU.

The pin numbers to be used for the QDEC are selected using the PSEL.n registers.

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NRF52820-QDAA-R Datasheet(PDF) 150 Page - Nordic Semiconductor