Difference between revisions of "Arduino/C3/Assembly-programming-through-Arduino/English"

Learning objectives

• Interface a seven-segment Display to Arduino board
• Write an assembly program to display a digit on seven-segment display and
• Display a digit on the seven segment display using 7447 IC.

Pre-requisites

• Electronics and
• Assembly language

Refer to the Additional reading material link of this tutorial to know more about:

• Arduino - Assembly code reference and
• Arduino ATmega328 Pin mapping.

System Requirement

• Arduino UNO Board
• Ubuntu Linux operating system version 14.04

External Devices

• Breadboard
• Arduino UNO Board
• Common Anode Seven-Segment Display
• 220 ohm Resistor
• Decoder 7447 IC
• Jumper Wires

Seven-segment display

Please refer to the basic level tutorial of this series to know more about seven segment display.

The Dot pin of the Seven Segment Display is connected to the pin 13 of Arduino.

Any one of the COM pins is connected to the +5V through a 220 ohm resistor.

AVRA is an assembler that will generate a hex file.

AVRDUDE is used to upload any hex file to the Arduino board.

> sudo apt-get install avra dude

sudo space apt hyphen get space install space avra space avrdude

Press 'Y' wherever there is a prompt during the installation, to confirm the configuration.

Installation will take some time to complete depending upon the internet speed.

Let us clear the screen.

ls space forward slash dev forward slash ttyACM asterisk

forward slash dev forward slash ttyACM0

Here ttyACM0 represents the port number of Arduino.

You may get a different port number. Make a note of your port number.

Def files for ATmega328P

We need to include this library file in the first line of the source code.

This allows the user to use Register and Bit name when writing assembly programs.

;program to turn on the Dot LED

These statements are ignored by the assembler and are not executed.

We had downloaded this file earlier and in my computer this is the path.

Note that we have to specify the entire file path.

ldi r16, 0b00100000

This sets pin PB5, that is digital pin 13 as output.

It tells the assembler to take a working register r16 and load a binary number into it.

ldi r17, 0b00000000

Rjmp Start

The program has to just keep running, in order for the LED to remain ON.

You can download and use it.

> cd /home/spoken/Assembly

> avra dot-blink.asm

Type, avra space dot hyphen blink.asm and press Enter.

Let us see the dot hyphen blink.hex file that is generated in the same folder.

avrdude -p atmega328p -c arduino -b 115200 -P /dev/ttyACM0 -U flash:w:dot-blink.hex

3:45

7:06,2:00,6:22

avrdude space hyphen p space atmega328p space hyphen c arduino space hyphen b space 115200 space hyphen capital P space forward slash dev forward slash ttyACM0 space hyphen capital U space flash colon w colon dot hyphen blink dot hex

Here ttyACM0 represents the port number of Arduino.

dot hyphen blink.hex is the file that is generated.

And press Enter.

Assignment 1

• Modify the same code to turn off the Dot LED.

The two common pins are connected to +5V through resistors.

/m328Pdef.inc"

Highlight 4 lines

Then make it as high or low according to our requirement.

ldi r16, 0b11111100

out DDRD, r16

ldi r16, 0b00000001

out DDRB, r16

These bits corresponds to the digital pins 2 to 8 on Arduino.

In our case, it is digit two.

ldi r17, 0b10010000

out PortD, r17

ldi r17, 0b00000000

out PortB, r17

Start:

Rjmp Start

This will make all the segments of SSD low, except c and g.

Let us clear the screen.

avrdude -p atmega328p -c arduino -b 115200 -P /dev/ttyACM0 -U flash:w:two.hex

Now change the filename as shown and press Enter.

Assignment 2

• Modify the above code to display any other digit from 0 to 9.

Show the image of the decoder:

We are using 7447 IC.

Show the pin image of 7447 IC

Vcc and the GND pins of the decoder are connected to +5V and the GND pins of Arduino.

Connect the A, B,C,D pins of the Decoder to pins 2,3,4,5 of Arduino.

Note that this decoder is compatible only with common anode seven segment display.

D C B A Decimal

0 1 0 1 5

A being the lowest significant bit (LSB) and D being the most significant bit (MSB).

For example, the number 5 is visible on the display when the A,B,C and D inputs are as shown here.

Open any text editor and type the following code.

.include "/home/user/m328Pdef.inc"

;Configure pins 2,3,4 and 5 on Arduino as Output

ldi r16, 0b00111100

out DDRD, r16

This means we are making digital pins 2 to 5 in Arduino as output pins.

2 to 5 pins in the Arduino are connected to A, B, C, D pins of decoder.

ldi r16, 0b00010100

out PORTD, r16

This will then be decoded as 5 in the seven segment display.

Rjmp Start

avrdude -p atmega328p -c arduino -b 115200 -P /dev/ttyACM0 -U flash:w:decoder.hex

Now change the filename as shown and press Enter.

Summary

• Interface a Seven-segment Display to Arduino board and
• Write an assembly program to display a digit on seven-segment display.
• Display a digit on the seven segment display using 7447 IC.

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Acknowledgement

More information on this mission is available at this link.

This is Priya from IIT Bombay signing off.

Thanks for joining.