Difference between revisions of "Interfacing Seven Segments with PIC16f877a"
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Revision as of 13:10, 4 May 2016
In the earlier tutorials we saw how to interface the Leds to PIC microcontroller and wrote the code to blink them. How ever the leds cannot be used to display any user information like numbers, char's etc. To display numeric values we can use seven segment displays.
In this tutorial we will interface a seven segment to PIC16f877a and display a single digit decimal counter(0-9).
Later same will be extended to multiplex 4 seven segment displays to generate a 4-digit counter.
Contents
Seven Segment Display
Well, the name 7 segments implies there are 7 LED segments arranged as shown in figure 1. After LEDs, these are the easiest interfaces to a microcontroller. There is also a decimal point or dp. It is used when decimal digits like 5.1 etc are displayed.
Applications
Seven segment are widely used in applications where digits[0-9] are required to be displayed.Although they also display letters A to F as shown in figure(2) simulation. This is a very simple and convenient way to display numbers in a bright fashion.
Form Factor
- Sizes:They come in various sizes; 0.28”, 0.3”, 0.32”, 0.36”, 0.39”, 0.4”, 0.5”, 0.56”, 0.6”, 0.8”, 1.0”, 1.2”, 1.5”, 1.8”, 2.0”, 2.3”, 3.0”, 4.0”, 5.0”, 7.0”)
- Colors: and varied colors too; Red, Green, Yellow, Orange, Blue, and White.
Working
Since these are basically LEDs arranged as a group they can either have anode in common or cathode thus they are named as Common-Anode/Common-Cathode displays.
- Common Cathode: In this type of segments all the cathode terminals are made common and tied to GND. Thus the segments a to g needs a logic High signal(5v) in order to glow.
- Common Anode: In this type of segments all the anodes terminals are made common and tied to VCC(5v). Thus the segments a to g needs a logic LOW signal(GND) in order to glow.
Below table shows the binary/hex values for displaying the digits on CommonAnode seven segment display.
| Digit | h | g | f | e | d | c | b | a | Hex Value |
| 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0xC0 |
| 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0xF9 |
| 2 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 0xA4 |
| 3 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0xB0 |
| 4 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0x99 |
| 5 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0x92 |
| 6 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0x82 |
| 7 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0xF8 |
| 8 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0x80 |
| 9 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0x90 |
Hardware Connection
Below image shows the hardware connection as per the table.
| a | b | c | d | e | f | g | h | COM |
|---|---|---|---|---|---|---|---|---|
| PD0 | PD1 | PD2 | PD3 | PD4 | PD5 | PD6 | PD7 | VCC |
Code: Single Segment
Below is the sample code to display single digit up counter.
Code: Four Segments
Below is the sample code for multiplexing four segments to display 4-digit up counter.
Video Tutorial
For those of you, who would like to watch instead of read we have made a video with all the gyan.
Downloads
Download the complete project folder from the below link:
https://github.com/ExploreEmbedded/ATmega32_ExploreUltraAvrDevKit/archive/master.zip
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