![]() ![]() Now, notice that to light up an LED, just the difference of potentials it’s connected to is important - so if both its leads are connected to GND, or if both its leads are connected to Vcc, the LED will not light up to light it up, we need the anode to be connected to Vcc and the cathode to GND and this is the only case in which it will light up. To make the programming easier, I’ll connect the pins representing segments A, B, C, D, E, F, G, DP to pins RD0 to RD7 respectively in that order, since then I’ll have RD0 pin controlling the segment A, RD1 pin controlling the segment B and so on. So, instead of connecting those 8 pins to GND, we’ll connect them to the PIC’s D register and by controlling which of the pins will be set to GND and which to Vcc we’ll be able to control which segments will light up and which not. However, if we would do that, the number 8 with a dot will be shown which is not what we want, so we’ll have to control somehow which of the segments would be lit so that a certain number would be displayed - and this can be done using the PIC microcontroller. To light them up, pins 3 and 8 are connected to Vdd (+5V) and the other 8 pins are connected through 220Ω resistors to ground. ![]() From the direction of the LEDs on the right schematic you can see that pins 3 and 8 are the common anode for the LEDs and the other pins are their cathode 1. Other pins are marked in a counter-clockwise manner - pins 1-5 are on the left side from top to bottom and pins 6-10 are on the right side from bottom to top, with the 10th pin in the top-right corner. Pin 1 is marked on the diagram and it’s the top-left pin. This 7-segment display has 10 pins total with 5 and 5 pins on either side. ![]() For my display, it’s shown in its datasheet (section “Internal Circuit Diagram”) and here’s how it looks like: previous setupwhere we programmed a PIC to blink an LEDīefore we start, disconnect the blinking LED and its resistor from pin RD0 which we connected there in the last part since we’re going to use that pin for the LED display.įirst, we need to determine how to wire up the LED display - to do so, find the datasheet of your display and look for its schematic and pinout.8x 220Ω resistors (the 8th resistor is for the decimal point).This will be useful for calibration of an IR sensor and generally for displaying any number output when debugging. In this post we’re going to connect a 7-segment LED display to a PIC18F452 and set it up so that it will show numbers from 0 to 9 in regular intervals, like a stopwatch. ![]()
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March 2023
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