Interfacing dot matrix LED display to 8051

Interfacing dot matrix LED display to 8051 microcontroller.

LED dot matrix display.

An LED dot matrix display consists of a matrix of  LED’s arranged in a rectangular configuration. The desired character or graphics can be displayed by switching ON /OFF  a desired configuration of LED’s. Common display configurations available are 7×5, 8×8, 7×15, etc. LED dot matrix can be used in simple display applications where the resolution is not a big concern.  The figure below shows the arrangement of LEDs in a typical 7×5 dot matrix display.


7x5 led dot matrix display

7x5 Led dot matrix display

Any individual LED or a group of LEDs in the matrix can be activated by switching the required number of rows and columns. For example, in the above figure if  Row1 is made high and Column1 is made low, the top left LED (address R1C1) will glow. As a demonstration, lets see how we can display letter “A” using the display. The tables given below shows the logic levels at each pin  for displaying A.

led dot matrix displaydot matrix led display

In the above diagram you can see that only one LED in a row will be ON at a time but any number of  LEDs in a column can be ON at a time.  That means the microcontroller’s port pin can directly drive a row but it requires  additional circuit for driving the column lines.  The circuit diagram for interfacing dot matrix display and 8051 microcontroller is shown below.

Circuit diagram.

interfacing dot matrix led display to 8051

ULN2003A driver IC.

The purpose of ULN2003A here is to drive the column lines of the display. ULN2003A is a high voltage (50V), high current (500mA per channel) darlington transistor array. Each IC has 7 channels with individual output clamp diodes. ULN2003A  an active high device, which means a logic high must be applied to the input  to make the corresponding output high. The input pins are designated as 1B, 2B, 3B, 4B, 5B, 6B, 7B while corresponding output pins are designated as 1C, 2C, 3C, 4C, 5C, 6C, 7C.  The pin configuration and simplified internal logic of ULN2003A is shown in the figure below.

uln2003 logic diagram

MOV P3,#00000000B        // initializes port 3 as output port
MOV P1,#00000000B        // initializes port 1 as output port
MAIN: MOV P3,#01111110B 
      MOV P1,#11111110B  
      ACALL DELAY        
      MOV P3,#00010001B  
      MOV P1,#11111101B  
      MOV P3,#00010001B  
      MOV P1,#11111011B  
      MOV P3,#00010001B
      MOV P1,#11110111B
      MOV P3,#01111110B
      MOV P1,#11101111B
      SJMP MAIN         // jumps back to the main loop
DELAY: MOV R6,#255D     // 1ms delay subroutine



Show Comments

15 thoughts on “Interfacing dot matrix LED display to 8051

  1. amanda

    hello sir, i was asked to design a dot matrix display system as a project in school and would really need assistance…… please contact me at the email above

  2. Connor Christensen


    I am experiencing difficulties programming the PIC and i am running out of time to complete my project, is there any chance in getting the PIC pre-programmed by a company or by the creator of this project.

    Thank you.

    • mohit

      to scroll u will need shift data byte from one ram location to another and then display the ram data on display and repeat this process

  3. nouman ahmad

    hy, i make dot matrix display and run same code which u wrote but it was not working , all leds were just on can u help me plz , rply me quick

  4. robert aungpe

    I must build a 8051 project for my class.
    At first I wanted a led message board (6X26), but then wanted a simpler project.
    Then I thought I’d try some sort of home alarm/indoor, outdoor light control/room occupancy. All, via keyboard, remotely interactive.
    Now after seeing your “interfacing dot matrix LED display to 8051”
    I want to make it my first ever programed 8051 project.
    It may not be worth writing home about but, its close to my current realm of knowledge. I need to get clarification on the programming steps from a friend in my network as I don’t fully comprehend the hex instruction.
    So thanks…for doing what you do.
    I have maybe 5 weeks to get’er done.
    I’ll need to assemble everything, so, if you have any recommendations, feel free to contact me.
    Thank you for opening this website.

    • praveen

      I used MCU8051IDE for writing,testing and hex file generation. You can also use MIDE-51 or anything like that. In system programming was used for burning the hex file into microcontroller. ISP programmer kits are readily available in the internet stores. Just google for it.


Leave a Reply

Your email address will not be published. Required fields are marked *