Texas Instruments CPG004DRV88 EVM Series, User Manual, Page: 9 / 21

%Duty Cycle =
PWM
¾
255 100
·
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The Windows Application
When the slider bar is moved across, the Duty Cycle indicator is updated accordingly. Resulting duty cycle
is an integer number between 0 and 100 and it is computed according to the equation:
(2)
The DRV8841-43 will offer the same ability to apply a PWM signal to each one of the INx pins.
Figure 10. PWM Signal on INx Pins
3.5 Operating the Stepper Motor (DRV8824)
3.5.1 Turning the Stepper Motor
The Windows application, in conjunction with the MSP430F1612 microcontroller, utilizes a series of timers
to coordinate the rate of steps sent to the device. Once all the control signals are configured accordingly,
(ENABLEn = LO, SLEEPn = HI, RESETn = HI; DIR, USMx can be HI or LO depending on preferred mode
of operation), the motor is ready to be turned.
The DRV88xx EVM allows for the possibility of coordinating step rates such that accelerating and
decelerating profiles are achieved. Both acceleration and deceleration are controlled by the same
parameters, acceleration rate and time base.
When the motor starts, it always starts at the slowed PPS speed (62 pulses per second). The controller
will accelerate the motor in order to reach the PPS speed. Acceleration rate is an 8-bit number (0 to 255)
that gets added to the current PPS speed and time base is an 8-bit number (0 to 255) that specifies how
many milliseconds will elapse from one speed increase to the next. Once the specified PPS speed has
been achieved, the acceleration stops.
When the motor stops, the inverse of the above description occurs.
9 SLVU361B – April 2010 – Revised October 2013 CPG004_DRV88xx Evaluation Modules
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