A serial-in parallel-out shift register (74HC164, 74HC595, CD4094…..) can be added to a 7-segment display. The adding of the shift register minimizes the number of pins used by the 7-segment display. This topic shows how to make a 4-digit digital counter with multiplexing and 74HC164 shift register using PIC18F4550 and CCS PIC C compiler.
Interfacing PIC18F4550 with multiplexed 7-Segment display with shift register circuit:
Example circuit schematic is shown below where a common anode 7-segment display and 74HC164N shift register are used.
Other shift registers such as 74HC595 and CD4094 can be used in this project.
Two buttons are used to increment and decrement the displayed number.
The following image from my hardware circuit:
Hardware Required:
- PIC18F4550 microcontroller —> datasheet
- Common anode 4-digit seven-segment display
- 74HC164 shift register —> datasheet
- 4 x 2N3906 PNP transistor —> datasheet
- 2 x Push button
- 4 x 10k ohm resistor
- 4 x 1k ohm resistor
- 7 x 100 ohm resistor
- 5V Power source
- Bread board and some jumper wires
- PIC microcontroller programmer (PICkit 2, PICkit 3…)
Digital up/down counter with PIC18F4550 CCS C code:
Example C code is the one below, it was tested with CCS C compiler version 5.051.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 | // Interfacing PIC18F4550 with 7-segment display // Common anode 7-segment display used #include <18F4550.h> #fuses NOMCLR INTRC_IO #use delay(clock=8000000) short s; // Used to know buttons position unsigned int j, digit, digit1, digit10, digit100,digit1000; unsigned long i = 0; unsigned int seg(unsigned int num) { switch (num) { case 0 : return 0xC0; case 1 : return 0xF9; case 2 : return 0xA4; case 3 : return 0xB0; case 4 : return 0x99; case 5 : return 0x92; case 6 : return 0x82; case 7 : return 0xF8; case 8 : return 0x80; case 9 : return 0x90; } } void main(){ setup_oscillator(OSC_8MHZ); // Setup internal oscillator @ 8MHz while(TRUE){ if(input(PIN_D4) && input(PIN_D5)) s = 1; if(s == 1) { if(input(PIN_D4) == 0) { s = 0; i++; if(i > 9999) i = 0; } if(input(PIN_D5) == 0) { s = 0; if(i < 1) i = 1; i--; } } digit = i % 10; digit1 = seg(digit); output_d(0x0F); // Turn off all displays for(j = 0x40; j > 0; j = j >> 1) { if(digit1 & j) output_high(PIN_B0); else output_low(PIN_B0); delay_us(10); output_high(PIN_B1); delay_us(10); output_low(PIN_B1);} output_d(0x07); // Turn on display for ones delay_ms(1); digit = (i / 10) % 10; digit10 = seg(digit); output_d(0x0F); // Turn off all displays for(j = 0x40; j > 0; j = j >> 1) { if(digit10 & j) output_high(PIN_B0); else output_low(PIN_B0); delay_us(10); output_high(PIN_B1); delay_us(10); output_low(PIN_B1);} output_d(0x0B); // Turn on display for tens delay_ms(1); digit = (i / 100) % 10; digit100 = seg(digit); output_d(0x0F); // Turn off all displays for(j = 0x40; j > 0; j = j >> 1) { if(digit100 & j) output_high(PIN_B0); else output_low(PIN_B0); delay_us(10); output_high(PIN_B1); delay_us(10); output_low(PIN_B1);} output_d(0x0D); // Turn on display for hundreds delay_ms(1); digit = (i / 1000) % 10; digit1000 = seg(digit); output_d(0x0F); // Turn off all displays for(j = 0x40; j > 0; j = j >> 1) { if(digit1000 & j) output_high(PIN_B0); else output_low(PIN_B0); delay_us(10); output_high(PIN_B1); delay_us(10); output_low(PIN_B1);} output_d(0x0E); // Turn on display for thousands delay_ms(1); } } |
Digital up/down counter with PIC18F4550 video:
The following video shows a hardware circuit of this project and how this counter works.
