Texas Instruments DRV8886AT User manual

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DRV8886AT Evaluation Module User's Guide
User's Guide
SLVUB16–February 2017
DRV8886AT Evaluation Module User's Guide
This document is provided with the DRV8886AT customer evaluation module (EVM) as a supplement to
the DRV8886AT datasheet (DRV8886AT 2-A Stepper Motor Driver With Integrated Current Sense). This
user's guide details the hardware implementation of the EVM.
Contents
1 Board Overview.............................................................................................................. 2
2 Introduction ................................................................................................................... 2
2.1 Connectors .......................................................................................................... 2
2.2 Test Points........................................................................................................... 3
2.3 Jumpers.............................................................................................................. 4
2.4 Motor Outputs ....................................................................................................... 4
2.5 Operation of the EVM .............................................................................................. 4
2.6 Motion Control Frame (Includes Start/Stop Steps and Move Steps) ........................................ 7
2.7 EVM documentation................................................................................................ 9
Appendix A Driver and GUI Installation Instructions ........................................................................ 10
List of Figures
1 Top View of Typical Board Configuration (EVM Provided May Vary) ................................................ 2
2 Connections (DRV8885 EVM Shown Has Similar Connections)...................................................... 3
3 GUI at Startup................................................................................................................ 4
4 Wake and Enable Toggle Buttons......................................................................................... 5
5 Reciprocate Toggle Button ................................................................................................. 6
6 Motor Motion Profile......................................................................................................... 7
7 Acceleration Profile.......................................................................................................... 8
8 Stop Conditions.............................................................................................................. 9
9 User Account Control Window............................................................................................ 10
10 EVM Setup Wizard......................................................................................................... 11
11 License Agreement ........................................................................................................ 11
12 Installation Folders......................................................................................................... 12
13 GUI Composer Runtime Selection....................................................................................... 12
14 Possible Upgrade Question............................................................................................... 13
15 Ready to Install............................................................................................................. 13
16 Completed................................................................................................................... 14
List of Tables
1 Connections to DRV8886AT Using External Microcontroller .......................................................... 3
Trademarks
MSP430 is a trademark of Texas Instruments.
Windows is a registered trademark of Microsoft Corporation.
All other trademarks are the property of their respective owners.

DRV8886AT
Motor
Connections
Power Connector
Microcontroller
Section
Micro
USB Header
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DRV8886AT Evaluation Module User's Guide
1 Board Overview
shows the top view of the printed circuit board (PCB).
Figure 1. Top View of Typical Board Configuration (EVM Provided May Vary)
WARNING
The DRV8886AT (U1) can operate at temperatures approaching
150ºC. This device should not be touched.
2 Introduction
The DRV8886AT customer EVM is a platform revolving around the DRV8886AT, a medium-voltage dual
H-bridge driver and highly-configurable power stage. This device has been optimized to drive a single
bipolar stepper with up to 16 degrees of internally generated microstepping.
The EVM houses an MSP430™ microcontroller and an USB interface chip. The USB chip allows for serial
communications from a PC computer where a Windows®application is used to schedule serial
commands. These commands can be used to control each of the device signals, and drive the stepper
motor by issuing the step commands at the desired rate.
The microcontroller firmware operates using an internal index mode.
This user's guide details the operation of the EVM, as well as the hardware configurability of the
evaluation module.
2.1 Connectors
The DRV8886AT EVM offers access to the VM (motor voltage) power rail through a terminal block (J1). A
set of test clips in parallel with the terminal block allows for the monitoring of the input power rail.
The user must apply the VM voltage according to recommended parameters listed in the data sheet.

Connect
USB
here
Connect Power and
Ground here
Connect Motor
here
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NOTE: The VDD voltage for the microcontroller is derived from the microUSB connector.
Figure 2. Connections (DRV8885 EVM Shown Has Similar Connections)
2.2 Test Points
A 0.100-inch pitch header connector (J4) provides access to every device signal in the event that a
different microcontroller is used. To disconnect the internal MSP430 microcontroller, remove the R3, R4,
R5, and R6 resistors, and resistor pack R7. Table 1 describes the connections available on the J4 header.
Each header pin is labeled on the evaluation module, and connects to a similarly named pin of the
DRV8886AT.
Table 1. Connections to DRV8886AT Using External
Microcontroller
Header Label Description
V3P3R 3.3 V after 0 Ωresistor
nFAULT Fault output
nSLEEP Sleep Mode input
RREF_R Chopping current selection
DIR DIR, Direction input
ENABLE ENABLE, Stepper motor enable
STEP STEP, Step input
USM0 M0, Step mode
USM1 M1, Step mode
TORQUE TRQ, Output current scale
DECAY_R Decay Mode select after 0-Ω
resistor
DVDD Internal supply voltage to set DAC
voltage
GND Ground

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2.3 Jumpers
The DRV8886ATEVM has no jumpers.
2.4 Motor Outputs
Two motor connectors are provided. shows the avaialable J2 and J3 connectors.
2.5 Operation of the EVM
Use the steps that follow to operate the EVM:
Step 1. Install the drivers and GUI. For instructions see Appendix A.
Step 2. Connect the wires of the stepper motor to the AOUT1, AOUT2, BOUT1, and BOUT2
terminals.
Step 3. Connect the VM power supply but do not apply power at this step.
Step 4. Connect the USB cable between the PC and the EVM. When the USB is connected to the
EVM, the status LED will begin to blink.
Step 5. Open the GUI. The GUI can be found in the start menu at Texas Instruments →
DRV8886_EVM →DRV8886_EVM X.Y.Z, where X, Y, and Z are the revision numbers. If a
shortcut was created, double-click on the shortcut to open the GUI. The GUI can take up to
30 s to establish a connection. If connection is not established, select the COM port under
the Options menu. The BaudRate is 9600.
NOTE: The DRV8886 EVM GUI is designed to control both the DRV8886AT EVM and the DRV8886
EVM. The GUI automatically identifies the device and changes the pulldown menus as
needed.
Step 6. Apply the desired voltage (6.5 to 37 V) to the VM and GND connections.
Step 7. Configure the current settings, step mode, decay mode, and torque to the desired values as
shown in Figure 3.
Figure 3. GUI at Startup

FS 1.232 VRREF_R
I Device_Full_Scale TORQUE StepModifier
1.232

§ ·
u u u
¨ ¸
© ¹
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The current is calculated using the VREF slider, the sense resistor value, the torque setting, and the
step mode setting using Equation 1.
where
• StepModifier is 0.71 for full step and 1 for other STEP MODE settings (1)
The number 1.232 is based on the maximum current allowed using the configuration. If VRREF = 0 V,
the maximum current is 1 A. The 12-bit DAC channel 1 is connected to the DRV8886AT analog input
RREF through a 15-kΩseries resistor. The DAC voltage begins at 1.232 V (0%) and ends at 0 V
(100%).
Step 8. After setting up the control signals for the DRV8886AT, select both the WAKE and ENABLE
toggle buttons to enable the DRV8886AT. When toggled, the WAKE or ENABLE status
toggles between red and green.
The WAKE toggle button, which controls the nSLEEP pin, is used to wake the DRV8886AT. The
ENABLE toggle button, which controls the ENABLE pin, is used to enable the DRV8886AT outputs.
A message stating Both WAKE and ENABLE must be green to enable the motor control buttons is
visible until both the WAKE and ENABLE toggle buttons are activated. When these two toggle buttons
have been activated, the message disappears and the Start/Stop Steps and Move # of Steps toggle
buttons are available.
If the WAKE or ENABLE toggle buttons are selected during motor operation, the motor is immediately
stopped and the STEP control signal from the microcontroller is reset.
Figure 4. Wake and Enable Toggle Buttons
Step 9. The DRV8886AT EVM is now awake and can be commanded to turn the motor. Turning the
motor occurs by either selecting the Start/Stop Steps,Move # of Steps, or Reciprocate toggle
button.
The Start/Stop Steps toggle button is used to run the motor indefinitely. The motor will accelerate to the
target speed and run until the Start/Stop Steps toggle button is selected. When the Start/Stop Steps toggle
button is selected, the red button changes to green, and the Move Steps and Reciprocate toggle buttons
are disabled.

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The Move Steps toggle button is used to allow movement of an exact number of steps. When the Move
Steps toggle button is selected, the Move Steps toggle button turns green, and the Start/Stop Steps and
Reciprocate toggle buttons are disabled until the number of steps have completed.
The Reciprocate toggle button is a special case of the Move Steps option. When selected, the motor
advances the specified number of steps in the direction initially set by the control inputs. After a short
pause, the motor then advances the same number of steps in the opposite direction. This sequence is
repeated until the Reciprocate toggle button is selected.
When the Reciprocate toggle button is selected, the Reciprocate toggle button turns green, and the
Start/Stop Steps and Move # of Steps toggle buttons are disabled until the Reciprocate toggle button is
set to red and the number of steps have completed.
Figure 5. Reciprocate Toggle Button
As an extra precaution, the motor can be stopped by selecting either the WAKE or ENABLE toggle
buttons. When selected, the STEP commands are stopped and the motor control buttons are disabled. To
re-enable motor control, set the WAKE and ENABLE toggle buttons to green.

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2.6 Motion Control Frame (Includes Start/Stop Steps and Move Steps)
The GUI has an area which offers access to a series of very useful stepper-control algorithms. This area
allows for determining the best current settings during running at various speeds, and when holding torque
is applied.
Note: Both the WAKE and ENABLE toggle buttons must be green to enable the motor control buttons.
Figure 6. Motor Motion Profile
Motor motion can only happen by using an acceleration profile which is described in Section 2.6.1. A
detailed explanation of each stepper control section follows (see Section 2.6.1 and Section 2.6.2).
This frame allows the configuration and running of the stepper with the direction as specified by the DIR
toggle button, with the current decay mode as specified under the Decay Mode drop-down menu, and the
microstepping resolution as specified under the STEP MODE drop-down menu.
The Motion Control frame gathers user information regarding stepping rate or motor speed. An
acceleration profile is used to start at a programmable speed and increase the stepping rate until reaching
the programmable desired speed.
An internal 8-MHz timer is used to measure time and generate the steps on a timely manner. The GUI
sends the information to the microcontroller as pulse-per-second (PPS) signal, and the microcontroller
transforms it into the respective clock cycles required for the timer to generate accurate STEP pulse
timing.
2.6.1 Start/Stop Steps
The acceleration profile is coded inside of the microcontroller to accept both the starting-speed PPS signal
and target-speed PPS signal as a clock cycle number. When the START STEPS command is issued (the
Start/Stop Steps toggle button is selected), the PWM timer generates steps at a rate specified by the start
speed PPS parameter.
When accelerating or decelerating, the PPS signal is adjusted every 32 ms based on the integer value of
PPSPS / 32 ms. If a nonzero value of PPSPS is entered, a minimum value of 1 is used. The step rate is
increased by the calculated value until the target speed is reached.
If the starting speed is greater than or equal to the target speed, the acceleration rate is set to 0. This
setting will prevent further speed changes until the motor is stopped, and new starting and target speeds
are entered. Texas Instruments recommends setting the starting speed to ½ the target speed to avoid this
scenario.
The very same START STEPS command computes how frequently automatic speed updates are issued
and a second timer is used to change the speed according to the programmed acceleration rate profile.
When the target speed PPS value is reached, the acceleration profile ends and the motor continues
running until the STOP STEPPER command is issued (the Start/Stop Steps toggle button is selected
again). When the stepper is commanded to stop, the controller performs the same actions as it did while
accelerating, but in reverse order to decelerate until the stop speed PPS value is reached, in which case
the motor fully stops.

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A second motor actuation is provided by the Move # of Steps and Reciprocate commands in which a
programmed number of steps are issued and then the motor is stopped. The acceleration and
deceleration profiles work similarly as before, except when the deceleration starts and when the motor
actually stops are a function of the Steps to Stop and deceleration rate parameters.
Figure 7 shows the acceleration profile and the role each parameter plays during speed computation.
Note: Both the WAKE and ENABLE toggle buttons must be green to enable the motor control buttons.
Figure 7. Acceleration Profile
2.6.2 Move Steps
To move the stepper a certain number of steps, use the move steps function to easily perform this action.
Parameters from the other frames are reused and their use is as previously explained. Two new
parameters have been added to properly control the limited number of steps actuation. These parameters
are described as follows:
Number of Steps — This parameter is the number of steps that the controller will issue.
Steps to Stop — The controller is continuously monitoring the step being issued and when the current
step is equal to the Steps to Stop parameter, a deceleration profile is issued. If the value of the
Steps to Stop parameter is larger than the number of steps, then the motor stops abruptly and
without undergoing a deceleration profile.
When a deceleration profile is issued, the controller decreases the speed until reaching the value of the
Stopping Speed parameter. If the # of Steps parameter is met before the deceleration profile is complete,
then the motor stops at the current speed. If the stop speed is met before all the number of steps is
issued, then the motor rotates at the stop speed value until all the steps are executed.
Ideally, the system should be tuned to resemble the case in which the controller executes all the
commanded steps at a speed as close as possible to the stop speed. In the event this is not possible
because of the particular parameters that were selected, stopping the motor at a speed very close to the
Stopping Speed parameter is often good enough to ensure good motion quality and application
performance.
Figure 8 shows the three conditions possible when stopping and the action taken.

1. Motor reaches stop speed at the stop speed. 2. Motor reaches stop speed before the stop speed is reached.
3. Motor runs out of steps before reaching stop speed.
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Figure 8. Stop Conditions
2.7 EVM documentation
The EVM schematics, layout, and BOM are provided in the DRV8886ATEVM Hardware Files. The GUI,
USB drivers, and MSP430F2617 source code are provided in the DRV8886ATEVM Firmware and GUI
software file.

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Driver and GUI Installation Instructions
Appendix A
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Driver and GUI Installation Instructions
A.1 Installing the FTDI Driver
In many cases, connecting the EVM to the computer will automatically install the FTDI driver. If necessary,
download the driver from the DRV8886ATEVM Firmware and GUI. Unzip the file and install the USB
driver following these steps based on the operating system:
• If using Windows XP, run \USB driver\CDM v2.10.00 WHQL Certified.exe.
• If using Windows 7, go to the \USB driver\ folder and right-click the CDM v2.10.00 WHQL Certified.exe
file. Then select Properties, go to the Compatibility tab, check the Run this program in compatibility
mode for option, select the Windows XP (Service Pack 2) option, and click the OK button. Next run the
CDM v2.10.00 WHQL Certified.exe file and click the Yes button in the pop-up window.
A.2 Installing the GUI
NOTE: The DRV8886 EVM GUI is designed to control both the DRV8886AT EVM and the DRV8886
EVM. The GUI automatically identifies the device and changes the pulldown menus as
needed. If the DRV8886 EVM GUI has been previously installed, installing the GUI again is
not required.
Locate the DRV8886_EVM_installer.zip file in the GUI folder. Unzip the file to any location and then
double click the GUIComposerApp-1.0.0.setup-win_2.0.6.exe file in the unzipped folder.
The installer will begin and the window shown in Figure 9 will appear.
Click the Yes button to continue (see Figure 9).
Figure 9. User Account Control Window