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# 3.2.18 Quadrature Encoder Interface (QEI)

The Quadrature Encoder Interface (QEI) module provides the interface to incremental encoders for obtaining mechanical position data. This module provides below features:

- Four input pins: two phase signals, an index pulse and a home pulse

- Programmable digital noise filters on inputs

- Count direction status

- Index (INDX) pulse to reset the position counter

- 32-bit position counter

- 32-bit position Initialization/Capture register

- 32-bit Compare Less Than and Greater Than registers

## Using The Library

Quadrature encoder signals Phase A, Phase B and an optional index signal and an optional home signal are connected to the QEI peripheral. The quadrature decoder in the QEI peripheral processes these signals with an internal counter to get the position, velocity and revolution count. The quadrature decoder increments or decrements the 32-bit Up/Down Counter for each change of state. The counter increments when QEA leads QEB and decrements when QEB leads QEA

## Library Interface

QEI peripheral library provides the following interfaces:

Functions

Name | Description
--- | ---
QEIx_Initialize | Initializes given instance of QEIx peripheral in quadrature mode
QEIx_Deinitialize | De-initializes QEIx peripheral
QEIx_IMVGatedValueSet | Sets the QEIx Index Match Value Configuration
QEIx_CounterModeSet | Sets the QEIx Counter mode
QEIx_PositionCaptureSet | Initializes the 32 bit position capture register value
QEIx_PositionCapture16bitGet | Returns the 16-bit position capture value
QEIx_PositionCaptureGet | Reads the 32-bit position capture value
QEIx_PositionCaptureDisable | Deasserts the QEIx position counter input capture
QEIx_PositionCaptureEnable | Sets the QEIx position counter input capture
QEIx_PhaseInputSwappedSet | Facilitates swapping of QEA and QEB
QEIx_PhaseInputSwappedGet | Gets the status of QEIx input phase swap configuration
QEIx_ModuloRangeSet | Sets the 32bit modulo count value
QEIx_PositionCountWrite | Sets the QEIx position count value
QEIx_PositionCount16bitRead | Returns the 16-bit position count value
QEIx_PositionCountRead | Reads the position count value
QEIx_Enable | Enables the QEIx peripheral
QEIx_Disable | Disables the QEIx peripheral

Data types and constants

Name | Type | Description
--- | --- | ---
QEI_MODE | Enum | Defines the QEI operating modes
QEI_IMV_STATE | Enum | Defines the QEI Index Match Value states