Texas Instruments Stellaris User manual

RDK-Stepper-03 Copyright © 2007–2009 Texas Instruments
User’s Manual
Stellaris® Stepper Motor Reference Design
Kit

2November 4, 2009
Copyright
Copyright © 2007–2009 Texas Instruments, Inc. All rights reserved. Stellaris and StellarisWare are registered trademarks of Texas Instruments.
ARM and Thumb are registered trademarks, and Cortex is a trademark of ARM Limited. Other names and brands may be claimed as the property
of others.
Texas Instruments
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Austin, TX 78746
Main: [phone]
Fax: [phone]
http://www.luminarymicro.com

Stellaris® Stepper Motor RDK User’s Manual
November 4, 2009 3
Table of Contents
Chapter 1: Stellaris® Stepper Motor Reference Design Kit Overview.........................................................9
Using the RDK....................................................................................................................................................9
Features..............................................................................................................................................................9
Motor Technology.............................................................................................................................................10
Introduction to Stepper Motors......................................................................................................................10
Chopper Control............................................................................................................................................11
RDK Specifications...........................................................................................................................................12
Electrical .......................................................................................................................................................12
Mechanical....................................................................................................................................................12
Chapter 2: User Interfaces.............................................................................................................................13
On-board User Interface...................................................................................................................................13
Speed Mode..................................................................................................................................................14
Position Mode...............................................................................................................................................14
Graphical User Interface...................................................................................................................................15
File Menu......................................................................................................................................................18
Configuration Window...................................................................................................................................18
Chapter 3: Hardware Description..................................................................................................................21
Block Diagram ..................................................................................................................................................22
Functional Description ......................................................................................................................................22
Microcontroller (Schematic Pages 1-2).........................................................................................................22
Output Power Stage (Schematic Page 3).....................................................................................................23
Control Interfaces (Schematic Page 4).........................................................................................................24
Software............................................................................................................................................................24
Chopper Control............................................................................................................................................24
Parameter Reference....................................................................................................................................26
Serial Protocol ..................................................................................................................................................26
Appendix A: Parameters................................................................................................................................27
Parameter Descriptions ....................................................................................................................................27
Motor Running Configuration........................................................................................................................28
Target Position..........................................................................................................................................28
Maximum Current .....................................................................................................................................28
Target Speed............................................................................................................................................28
Acceleration ..............................................................................................................................................28
Deceleration..............................................................................................................................................29
Motor Drive Configuration.............................................................................................................................29
Winding Resistance ..................................................................................................................................29
PWM Frequency .......................................................................................................................................29
Fixed Rise Time........................................................................................................................................29
Drive Current.............................................................................................................................................30
Holding Current.........................................................................................................................................30
Control Mode ............................................................................................................................................30
Decay Mode..............................................................................................................................................31
Step Mode.................................................................................................................................................31
Off Blanking Time .....................................................................................................................................31

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Appendix B: Schematics................................................................................................................................33
Appendix C: PCB Component Locations.....................................................................................................39
Appendix D: Bill of Materials (BOM) .............................................................................................................41

Stellaris® Stepper Motor RDK User’s Manual
November 4, 2009 5
List of Tables
Table 1-1. RDK Motor Specifications .............................................................................................................11
Table 2-1. Description of GUI Main Window Controls....................................................................................16
Table 2-2. Description of Configuration Controls............................................................................................19
Table 3-1. Current Monitoring Circuits............................................................................................................23
Table A-1. Parameter Configuration Summary...............................................................................................27

6November 4, 2009

Stellaris® Stepper Motor RDK User’s Manual
November 4, 2009 7
List of Figures
Figure 1-1. Stepper Motor................................................................................................................................10
Figure 1-2. Stepper Speed-Torque Curve.......................................................................................................11
Figure 2-1. On-board User Interface................................................................................................................13
Figure 2-2. Stepper Main GUI Window............................................................................................................15
Figure 2-3. Configuration Window ..................................................................................................................19
Figure 3-1. Stepper Motor Control RDK Layout...............................................................................................21
Figure 3-2. Block Diagram...............................................................................................................................22
Figure 3-3. Chopper Waveform Generation ....................................................................................................25
Figure 3-4. Current Control Software Flow......................................................................................................25

8November 4, 2009

November 4, 2009 9
Stellaris® Stepper Motor Reference Design Kit
Overview
Stellaris Reference Design Kits (RDKs) from Texas Instruments accelerate product development
by providing ready-to-run hardware, a typical motor, and comprehensive documentation including
hardware design files. Designers without prior motor control experience can successfully
implement a sophisticated motor control system using the Stepper Motor Control RDK (Stepper
RDK).
Using the RDK
The recommended steps for using the RDK are:
Follow the Quickstart Guide included in the kit.
The Quickstart guide will help you get the motor up and running in minutes. It also contains
important safety information that should be read before using the RDK.
Use the RDK GUI software to evaluate and optimize motor performance.
The RDK GUI gives real-time access to more than a dozen operating parameters. Parameters
and data transfer between the RDK control board and PC over a USB cable.
Customize and integrate the hardware and software to suit an end application.
This User's Manual and the Software Reference Manual are two important references for
completing your project. Software can be programmed in the motor control board using either
the RDK GUI software or using a JTAG debug interface (available from leading development
tools vendors).
Features
The Stepper RDK's primary application is driving NEMA17, NEMA23, and NEMA34 stepper
motors rated at up to 80 V at 3 Amps. The Stepper RDK uses software-based chopper control in
order to operate the motor at both high torque and high-step rates. The Stepper RDK has the
following features:
Advanced chopper control of bipolar stepper motors
Flexible platform accelerates integration process
Fast and slow decay modes
Full-Step, Half-Step, Micro-Step, and Wave modes
High step rates up to 10,000 steps/sec (with suitable motor)
Programmable holding current
Integrated USB Virtual COM port
Bootloader for firmware upgrades over serial port
Support for external debugger through standard 20-pin ARM header
CHAPTER 1

Stellaris® Stepper Motor Reference Design Kit Overview
10 November 4, 2009
Motor Technology
Introduction to Stepper Motors
Stepper motors are synchronous DC motors which rotate in precise increments as their coils are
energized. Stepper motors typically have step angles of 0.9°, 1.8°, 7.5°, or 15°. The motor in the
RDK has a step angle of 1.8° for a total of 200 steps per revolution. Figure 1-1 shows a detailed
photo of the NEMA23 stepper motor included in the RDK.
There are several different families of steppers motors, some with and some without permanent
magnets (PM). The most common type in industrial applications is known as a hybrid stepper
motor because it combines attributes from PM and non-PM motor construction.
Figure 1-1. Stepper Motor
The rotor on a hybrid stepper motor typically has 200 teeth made from a suitable magnetic
material and surrounding one or more powerful embedded magnets. As the stator phase is
energized, the opposing pole in the next rotor tooth is attracted, resulting in a single-step.
Note that the torque curve of stepper motors is far from linear (see Figure 1-2). For each step, the
motor develops peak torque when the rotor teeth are offset by one-quarter tooth pitch from the
opposing pole in the energized phase. Also, overall motor torque drops considerably as motor
speed increases. For this reason stepper motor torque is specified as the holding torque, or torque
with no angular motion.
Stator coils
Stator teeth 50 rotor teeth
on each pole
South pole
North pole
Double-stack motor has
2 sets of magnets
Front bearing
Shaft