Embedded Systems Design, 2nd Edition

186 Embedded systems design

wave form. With a large mark and a low space, the voltage is

applied to the motor for almost all of the cycle time, and thus the

motor will rotate very quickly. With a small mark and a large

space, the opposite is true. The diagram shows the waveforms for

medium, slow and fast motor control.

The only difference between this method of control and that

for a simple on-off switch is the timing of the pulses from the

digital output to switch the motor on and off. There are several

methods that can be used to generate these waveforms.

Software only

With a software-only system, the waveform timing is done

by creating some loops that ...