Texas Instruments DRV8811EVM manual Pulses Per Sec ond, Accel, Time, B ase, Step Rate

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The DRV8811_RD customer 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 pulses per second (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.

Pulses Per Sec ond

	Accel
Time	Rate
B ase

Figure 8. Step Rate

When the motor is commanded to stop, the inverse of the description above occurs.

The Windows Application frame to control speed, acceleration and deceleration, as well as motor start and stop, looks as portrayed in Figure 9.

Figure 9. Speed Control Frame

SLVA344A–July 2009–Revised September 2009 Laser and Motor Drives 11

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