SPRUJ87 june   2023

 

  1.   1
  2.   Description
  3.   Get Started
  4.   Features
  5.   Applications
  6.   6
  7. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
    5. 1.5 Important Usage Notes
  8. 2Hardware
    1. 2.1  Assembly Instructions
    2. 2.2  Power Requirements
    3. 2.3  Interfaces
    4. 2.4  LaunchPad Specific Features
    5. 2.5  Jumper Information
    6. 2.6  Mechanical
    7. 2.7  System Power
    8. 2.8  BLDC Motor Drive
    9. 2.9  Motor Current Feedback
    10. 2.10 Motor Position Encoder Feedback
  9. 3Hardware Design Files
    1. 3.1 Schematics
    2. 3.2 PCB Layouts
    3. 3.3 Bill of Materials (BOM)
  10. 4Additional Information
    1. 4.1 Trademarks
    2. 4.2 Terminology
  11. 5References

2.10 Motor Position Encoder Feedback

The AM2x MCU PRU provide a flexible 2-wire and 4-wire absolute encoder feedback path for interfacing to high performance industrial and safety critical absolute encoders and protocols.

A set of THVD1450 RS-485 transceivers is used to convert the 3.3V logic level transmit, receive, clock and transmit-enable signals from the AM2x MCU to the expected RS-485 line-levels with proper termination. A 4-channel 1:2 MUX (U35, and U24) are used to select between the 2-Wire RS-485 path option (TX/RX on a single differential pair) vs. the 4-Wire RS-485 path option (TX/RX differential pair and a separate clock differential pair). 2-Wire/4-Wire mode selection is done through the J24 and J25 jumpers.

GUID-42B4E770-9794-469E-9729-03F6D59E7E67-low.png Figure 2-25 PRU Absolute Encoder Feedback – PRU Mapping

With this combination of RS-485 transceivers and configurable 2-wire/4-wire peripheral support, the AM2x MCU can support a wide range of RS-485 based absolute encoders such as Heidenhain EnDat22, SICK HIPERFACE DSL, Tamagawa, Nikon and others. See the AM243x MCU SDK and the AM263x MCU SDK for an array of encoder interface software examples.

Axis-1 Absolute Encoder Feedback

The axis-1 encoder PRU path implementation is multiplexed between the compatible LP-AM243 and LP-AM263 pins which utilize different parts of the LaunchPad pinout. Jumper J28 selects between the LP-AM243 and LP-AM263 paths. Jumper J24 is used to select between 2-wire and 4-wire RS-485 options.

GUID-16B8C5D2-A8C5-4FD1-9E9E-997927F65701-low.png Figure 2-26 Axis-1 - PRU Absolute Encoder Feedback

Axis-2 Absolute Encoder Feedback

The axis-2 path is direct from the BoosterPack headers to the U24 MUX and on to the RS-485 transceivers. This axis-2 path is only compatible with the LP-AM243 LaunchPad pinout. Jumper J25 is used to select between 2-wire and 4-wire RS-485 options.

GUID-B1C44A92-86C6-4554-8EDB-F25938B8F71B-low.png Figure 2-27 Axis-2 - PRU Absolute Encoder Feedback