Target Speed
Starting Speed
Acceleration Rate
Number Of Steps
Steps To Stop
Stopping Speed
The Windows Application
22
SLVU701B – March 2012 – Revised July 2019
Copyright © 2012–2019, Texas Instruments Incorporated
DRV8834 Evaluation Module
An internal 8-MHz timer is used to measure time and generate the steps on a timely manner. The
Windows application will transform the entered number of PPS and transform it into the respective clock
cycles needed for the timer to generate accurate STEP pulse timing.
The acceleration profile is coded inside of the microcontroller to accept both the starting speed PPS and
target speed PPS as a clock cycle number. When the start steps command is issued (Starts Steps button
is pressed), an interrupt service routine (ISR) generates steps at a rate specified by the start speed PPS
parameter.
The very same start steps command computes how frequent automatic speed updates are issued and a
second timer is used to change the speed according to the programmed acceleration rate profile.
Once the target speed PPS is reached, the acceleration profile ends and the motor stays running until the
stop stepper command is issued (Stop Steps button). When the stepper is commanded to stop, the
controller does exactly as it did while accelerating, but in reverse as to achieve deceleration until the stop
speed PPS is reached, in which case the motor fully stops.
A second motor actuation is provided by the move steps command in which a programmed number of
steps are issued and then the motor stopped. The acceleration and deceleration profiles work similarly as
before, except when the deceleration starts to happen and when the motor actually stops are a function of
the steps to stop and deceleration rate parameters.
shows the acceleration profile and the role each parameter plays during speed computation.
Figure 29. Acceleration Profile
The following controls are available within the motor control frame:
Start Speed PPS:
Number of pulses per second (or full steps per second) at which the motor will rotate at
the beginning of operation. The SW will only allow a number as small as 200 PPS and can be taken to a
number as large as 65535 PPS.
Target Speed PPS:
Number of pulses per second (or full steps per second) at which we want the motor
to operate. The acceleration profile will start from the start speed PPS and increase stepping rate until
reaching the desired speed PPS. The SW will only allow a number as small as 200 PPS and can be taken
to a number as large as 65535 PPS.
Acceleration Rate (0-5000):
A number from 0 to 5000 which acts as a stepping rate modifier to increase
the start speed PPS up to target speed PPS.
Stop Speed PPS:
Number of pulses per second (or full steps per second) at which the motor will stop
rotating after the stop stepper command is invoked and the deceleration profile is issued. The deceleration
profile modifies the stepper speed from the target speed and into the stop speed.
4.8
Move Steps Frame
If the user desires to move the stepper a certain number of steps, this can be easily accomplished by
using the move steps function. Parameters from the other frames are reused and its utilization is as
explained previously. Two new parameters have been added to properly control the limited number of
steps actuation.
Number of Steps:
Amount of steps 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 steps to stop is larger than the
number of steps, then the motor stops abruptly and without undergoing a deceleration profile.
