Quadrature Decoder Tool

QDC tool functional and wiring diagram

The quadrature edge detector is fed by a pair of signals named A and B delivered by a phase-quadrature motion encoder device.

The source selectors allows following pairs of adjacent input-capable GPIO input lines to be selected as A/B input sources: DIN11-DIN12, DIN21-DIN22, TTLIO11-TTLIO12, TTLIO21-TTLIO22, IIN11-IIN12, IIN13-IIN14, IIN21-IIN22, and IIN23-IIN24.

The tool includes the following function blocks:

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A quadrature edge detector

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A backward motion compensator

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A 32-bit position counter

The tool delivers:

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One I/O Toolbox event stream named QDC<i>.

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A direction status bit indicating the direction of the motion.

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A position status word indicating the position offset.

The Quadrature Decoder Tool decodes the A/B signals and delivers 1, 2, or 4 events every A/B cycle, possibly filtered by the backward motion compensator.

Quadrature Edge Detector

The quadrature edge detector analyzes the transitions on the A/B lines. It delivers:

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An event stream, named U, having 1, 2, or 4 events every A/B cycle according the QuadratureDecoderToolActivation settings

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An identification of the phase between A and B (A leads B or vice-versa)

Quadrature edge detector waveforms

The U stream may be filtered by the backward motion compensator before being delivered to the QDC<i> output.

The phase indication may be inverted according to the QuadratureDecoderToolForwardDirection settings before being delivered to the Direction output.

Backward motion compensator

The backward motion compensator (BMC) filters the U stream according to the QuadratureDecoderToolOutputMode setting.

When set to Unfiltered, all the events of the U stream are delivered to the QDC<i> output:

BMC waveforms - Unfiltered

When set to ForwardOnly, only the events corresponding to the forward direction are delivered to the QDC<i> output:

BMC waveforms - Forward Only

When set to FirstPassForwardOnly, only the events corresponding to the first pass in the forward direction are delivered to the QDC<i> output:

BMC waveforms - First Pass Forward Only

Position Counter

The position counter increments by 1 for any U event corresponding to the forward direction and decrements by 1 for the backward direction.

The counter can be reset using the QuadratureDecoderToolPositionReset command.