EQEP CW/CCW Example

Table of Contents

• Introduction
  • Example Description
  • Configuration Details
• External Connections
  • AM261x-SOM
  • AM261x-LP
• Watch Variables
• Supported Combinations
• Steps to Run the Example
• Sample Output
• See Also

Introduction

This example demonstrates the use of eQEP (Enhanced Quadrature Encoder Pulse) module to measure position, direction, frequency and speed from CW/CCW input pulses. The example emulates encoder signals using GPIO outputs and timer-based interrupts.

EQEP CW/CCW Input pulses, Index Pulse visible at count 0

Example Description

The example configures:

• Two GPIO outputs to generate CW and CCW pulses that emulate encoder signals
• A third GPIO output to generate index pulses
• eQEP module in QMA Mode 2 (Active Pulse High)
• Timer-based interrupts to generate the pulses
• Unit timeout period of 10ms for speed measurement

The example demonstrates:

• Position counting in both CW and CCW directions
• Direction detection
• Frequency measurement
• Speed calculation in RPM
• QMA error detection

Configuration Details

• Encoder resolution: 1000 counts/revolution
• Pulse pattern: Direction changes everytime eqep ISR is triggered
• Pulse frequency: 2.5kHz (150 RPM)
• Index pulse generated using simulated count at pos=0
• Unit timeout period: 10ms

External Connections

The following GPIO pins can be monitored with an oscilloscope to view the generated encoder signals:

AM261x-SOM

• GPIO49: eQEP Phase A signal
• GPIO50: eQEP Phase B signal
• GPIO48: eQEP Index Signal

AM261x-LP

• GPIO49/J4.38: eQEP Phase A signal
• GPIO50/J4.37: eQEP Phase B signal
• GPIO48/J4.36: eQEP Index Signal

Watch Variables

The following variables can be monitored by pausing the program to observe the eQEP measurements:

• gEncoderState: Global structure for all calculations

Supported Combinations

Parameter	Value
CPU + OS	r5fss0-0 nortos
Toolchain	ti-arm-clang
Board	am261x-som, am261x-lp
Example folder	examples/drivers/eqep/eqep_cw_ccw

Steps to Run the Example

1. Import and build the project for your target configuration
2. Connect an oscilloscope to monitor the GPIO outputs if desired
3. Load and run the program
4. Monitor the watch variables to observe:
   • Position counting
   • Direction changes
   • Speed measurement
   • QMA error detection

Sample Output

The example will display position, direction, frequency and speed measurements via UART:

EQEP Position Speed Test Started ...
EQEP Validation Passed
Results:
  Frequency: 2500 Hz
  Speed: 150.00 RPM
  Direction: Counter-clockwise
All tests passed successfully!

See Also

• EQEP
• GPIO