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7-Segment Display
This page gives instructions on using Kanda 7-segment display modules with STK200 and STK300 kits. The module plugs in to any Port header on the board.7-Segment Display
This table gives the hexadecimal encodings for showing the digits 0 to F on 7-segment display using Kanda 10-way connector. 0 is segment On
| Digit | gbdf(dp)eac | g | b | d | f | dp | e | a | c |
|---|---|---|---|---|---|---|---|---|---|
| 0 | 0x88 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 0 |
| 1 | 0xBE | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 0 |
| 2 | 0x19 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 |
| 3 | 0x1C | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
| 4 | 0x2E | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 0 |
| 5 | 0x4C | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 |
| 6 | 0x48 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 0 |
| 7 | 0xBC | 1 | 0 | 1 | 1 | 1 | 1 | 0 | 0 |
| 8 | 0x08 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 |
| 9 | 0x0C | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 |
| A | 0x28 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 |
| b | 0x4A | 0 | 1 | 0 | 0 | 1 | 0 | 1 | 0 |
| C | 0xC9 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 |
| d | 0x1A | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 0 |
| E | 0x49 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 |
| F | 0x69 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | 1 |
Display Segments
C Code Example
This code is written for WinAVR running in Atmel Studio. Please check that the device selected in Project > Configuration Options matches your target device or the code will not run.The code justs counts Hexidecimal from 0-F and repeats. It has a 1 second delay between characters, on a 1MHz clock. Alter F_CPU constant to match your target clock speed, 8MHz on an STK200 board.
To change the count to Decimal (0-9), change value of dec-hex variable.
To change Port, alter PORT_7_SEGMENT and DDR_7_SEGMENT constants.
/* WinAVR Code to display 0-9 or 0-F to 7-segment display.
Change Variable dec_hex in Main function to swap between
hex and decimal. Warning: clock speed is defined as 1MHz (F_CPU) because new
AVR devices have default 1MHz Internal RC. Change F_CPU to match your clock speed.
There are 7-segments + decimal point (DP) and they are active low, that is 0 = segment on.
DP is always off (1).
PIN wiring is
Pin Segment
7 g
6 b
5 d
4 f
3 DP
2 e
1 a
0 c */
// clock speed for delay
#define F_CPU 1000000UL // New AVR devices are at 1MHz Internal clock
// STK200 board has 8MHz cystal
#include <avr/io.h>
#include <util/delay.h>
//Configurations
//**************
// Change constant here to change port used by 7-segment
#define PORT_7_SEGMENT PORTB
#define DDR_7_SEGMENT DDRB
void SevenSegment(uint8_t count,uint8_t dp, uint8_t dec_hex)
{
/* This function shows value of count on display the decimal point is displayed if dp=1
Note:
count must be less than 10 for decimal, or less than 16 for Hex. */
if(count <dec_hex)
{
switch (count)
{
case 0:
PORT_7_SEGMENT=0b10001000;
break;
case 1:
PORT_7_SEGMENT=0b10111110;
break;
case 2:
PORT_7_SEGMENT=0b00011001;
break;
case 3:
PORT_7_SEGMENT=0b00011100;
break;
case 4:
PORT_7_SEGMENT=0b00101110;
break;
case 5:
PORT_7_SEGMENT=0b01001100;
break;
case 6:
PORT_7_SEGMENT=0b01001000;
break;
case 7:
PORT_7_SEGMENT=0b10111100;
break;
case 8:
PORT_7_SEGMENT=0b00001000;
break;
case 9:
PORT_7_SEGMENT=0b00001100;
break;
//hex only
case 10:
PORT_7_SEGMENT=0b00101000; //A
break;
case 11:
PORT_7_SEGMENT=0b01001010; //b
break;
case 12:
PORT_7_SEGMENT=0b11001001; //C
break;
case 13:
PORT_7_SEGMENT=0b00011010; //d
break;
case 14:
PORT_7_SEGMENT=0b01001001; //E
break;
case 15:
PORT_7_SEGMENT=0b01101001; //F
break;
}
if(dp)
{
//if decimal point should be displayed make DP bit Low
PORT_7_SEGMENT&=0b11110111;
}
}
else
{
//This symbol on display shows that count was greater than 9 or 15
//so display can't handle it
PORT_7_SEGMENT=0b11011111;
}
}
int main()
{
//Setup
DDR_7_SEGMENT=0xFF; //All output
PORT_7_SEGMENT=0xFF; //All segments off
uint8_t count=0;
uint8_t dec_hex=16; //change to 10 for decimal
while(1) //loop forever
{
SevenSegment(count,0, dec_hex);
count++;
if(count==dec_hex)
{
count=0;
}
_delay_ms(1000);
}
}
Assembler Code Example
/*
7-segment display on PORTB increments when button 0 is pressed (PortD)
There are 7-segments + decimal point (DP) and they are active low,
that is 0 = segment on. DP is always off (1).
Change include file for other devices.
PIN wiring is
Pin Segment
7 g
6 b
5 d
4 f
3 DP
2 e
1 a
0 c
*/
.include "m16def.inc" // change for other devices
.def temp = r16
.def counter = r17
.def coarse = r18 // delay routine for switch debounce
.def middle = r19
.def fine = r20
// change to change ports
.equ SEG7_PORT= PORTB
.equ SEG7_DDR = DDRB
.equ BUTTON_PORT= PORTD // Port write register
.equ BUTTON_DDR = DDRD // Port direction register
.equ BUTTON_INPUT = PIND // Port read register
.cseg
.org 0
rjmp Reset
// store values to drive 7-segment display
segments: //digits 0-9
.db 0b10001000, 0b10111110, 0b00011001, 0b00011100
.db 0b00101110, 0b01001100, 0b01001000, 0b10111100
.db 0b00001000, 0b00001100
//hex only A-F
.db 0b00101000, 0b01001010, 0b11001001, 0b00011010
.db 0b01001001, 0b01101001
Reset:
LDI temp,LOW(RAMEND) ; Set up stack - needed for sub-routines
OUT SPL,temp
LDI temp,HIGH(RAMEND)
OUT SPH,temp
ser temp ; 7-SEG Port as outputs (FFh)
out SEG7_DDR, temp
ldi temp, 0b11111110 ; BUTTON.0 as input, 0=input
out BUTTON_DDR, temp
Reset_counter:
clr counter ; Initialize to 0
// load pointer registers with address of segments
ldi Zl,low(segments * 2) ; * to convert cseg address to byte addressing
ldi Zh,high(segments * 2)
Start:
lpm temp,Z+ ;read a byte from 'segments' and increment Z
out SEG7_PORT, temp // output to 7-segment display
loop_while_button_held:
sbic BUTTON_INPUT,0 // button pressed = 0, so skip
rjmp loop_while_button_held // jump if pin is low
rcall delay // switch debounce
inc counter
cpi counter, 16 //change to 10 for decimal
brne Start // return to start if count not reached
rjmp Reset_counter
/// delay subroutine for switch debounce.
// change value of coarse to change switch response rate
// For example, $0F for 8MHz
delay: ldi coarse,$02
delay1: ldi middle,$FF
delay2: ldi fine,$FF
delay3: dec fine
brne delay3
dec middle
brne delay2
dec coarse
brne delay1
ret
Module Schematic
7-Segment Module