Seven Segment Multiplexing using PIC18F4550 Microcontroller
As explained earlier, a seven segment interfaced with PIC uses almost an entire port (minimum 7 pins) to display a value. But a real time application, like watch, calculator etc., usually requires at least 3-4 seven segments. In such a case it is not advisable to use a port of the controller for each seven segment. In these cases, multiplexing technique is used to work with more than one seven segment. Here multiplexing of four seven-segments has been explained with PIC18F4550 to display four-digit count from 0000 to 9999.
The data pins (a-g) of all the seven-segments are connected to a single port (Port D*) as shown in the circuit diagram. Transistors BC547 are connected to COM pins of seven-segment for switching. The switching of COM pins is controlled by four pins of PortA.
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