How to interface MAXIM’s DS1868 digital potentiometer with a PIC microcontroller
An analog potentiometer has three terminals, two of them are connected to the end-points of a resistive element of fixed resistance. The third terminal (known as wiper) can be slided to any point in between the two ends of the resistive element, thus varying the resistance between the wiper and any other end. A digital potentiometer mimics the same functionality except there are only finite wiper positions, which is is digitally controlled.
The DS1868 is a dual digital potentiometer chip from MAXIM, where each potentiometer is composed of 256 resistive sections. Between each resistive section and both ends of the potentiometer are tap points which are accessible to the wiper. The position of the wiper on the resistor array is set by an 8-bit value that controls which tap point is connected to the wiper output. Both potentiometers can also be connected in series (or stacked) for an increased total resistance with the same resolution, or multiple of DS1868 chips can also be cascaded. The DS1868 is offered in three standard resistance values which include 10, 50, and 100 K? versions.
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