Article: Microcontroller's single I/O-port line drives a bar-graph display.(design ideas)

Instrument designs featuring a digital display may benefit from a secondary display that provides an analog version of the displayed parameter. A bar-graph display provides an easily interpreted graphical indicator that allows comparison with its full-scale value, but a conventional microcontroller-based design uses at least one eight-line I/O port to drive an eight-segment-bar-graph LED display.

As an alternative, some microcontrollers include a PWM (pulse-width-modulated) output. You can minimize the number of required I/O lines by using the PWM output to drive National Semiconductor's LM3914 bar-graph-display-driver circuit or an equivalent. In operation, the ...

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