Book Analog Interfacing to Embedded Microprocessors
This may not be the
position you want, and it probably isn’t the position it was last in. The only
way to insure that the digital pot remembers its position is to use nonvolatile
storage. On power-up, the software looks up the last position of each pot and
sets the pot accordingly. The software also needs to insure that the power-up
state of the potentiometer doesn’t damage whatever it is controlling.
Potentiometers are available that retain their setting when power is turned
off. Xicor makes a series of EEPOT devices with SPI, I2C, and increment/
decrement interfaces. The EEPOT series of parts contain an EEPROM
and remember their settings.
160 Analog Interfacing to Embedded Microprocessors
Motors 7
Motors are a key component of many embedded systems, as they provide
a means to control the real world. Motors are used for everything from
annaabi.ee 
