Thursday, January 15, 2015

How to identify pin 1 of 8x8 LED Matrix

This post show how to identify pin 1, and pin 16, of 8x8 LED Matrix.


Part I: Row Anode Column Cathode 8x8 LED Matrix, 1588BS as example. Current flow from pin 1 to pin 16 to make LED on row 5 col 8 ON.

Use the example of Row-Column Scanning an 8x8 LED matrix to show it work.

The connection between Arduino Uno and 8x8 LED Matrix is show here:

(It's recommended to add 220 ohm resisters to limit the current)

We need a test program to verify our connection, visit http://goo.gl/tXySxV, copy the example sketch of Walking bit on 8*8 LED Matrix, and download to Arduino Uno.


If your 8x8 LED Matrix have no marking for pin 1, we can use a multimeter to identify pin 1, and also pin 16.

This scheme diagram show when we apply +ve on pin 1 and -ve on pin 16, the LED on row 5 col 8 will be turn on.

Switch multimeter to diode test, the red lead will be +ve and black lead will be -ve.

Refer to the below video:
There are 4 possibility of pin 1 and 16, only one case will turn on a LED. When the LED (row 5 col 8) on, the pin connected to the RED lead of multimeter is pin 1.




Part II: Row Cathode Column Anode 8x8 LED Matrix, 1088AS as example. Current flow from pin 16 to pin 1 to make LED on row 5 col 8 ON.


Same procedure as in part I, with pin 1 on BLACK lead of multimeter.


Working example, refer to next post "Arduino Uno + SPI 8x8 LED Matrix, with MAX7219 LED driver".


2 comments:

  1. Replies
    1. /*
      * Modify from Row-Column Scanning an 8x8 LED matrix tutorial
      * http://arduino-er.blogspot.com/
      */
      /*
      Row-Column Scanning an 8x8 LED matrix with X-Y input

      This example controls an 8x8 LED matrix using two analog inputs

      created 27 May 2009
      modified 30 Aug 2011
      by Tom Igoe

      This example works for the Lumex LDM-24488NI Matrix. See
      http://sigma.octopart.com/140413/datasheet/Lumex-LDM-24488NI.pdf
      for the pin connections

      For other LED cathode column matrixes, you should only need to change
      the pin numbers in the row[] and column[] arrays

      rows are the anodes
      cols are the cathodes
      ---------

      Pin numbers:
      Matrix:
      * Digital pins 2 through 13,
      * analog pins 2 through 5 used as digital 16 through 19
      Potentiometers:
      * center pins are attached to analog pins 0 and 1, respectively
      * side pins attached to +5V and ground, respectively.

      This example code is in the public domain.

      http://www.arduino.cc/en/Tutorial/RowColumnScanning

      see also http://www.tigoe.net/pcomp/code/category/arduinowiring/514 for more
      */


      // 2-dimensional array of row pin numbers:
      const int row[8] = {
      2, 7, 19, 5, 13, 18, 12, 16
      };

      // 2-dimensional array of column pin numbers:
      const int col[8] = {
      6, 11, 10, 3, 17, 4, 8, 9
      };

      // 2-dimensional array of pixels:
      int pixels[8][8];

      int posX = 7;
      int posY = 7;
      int count = 30;
      bool bg = false;

      void setup() {
      // initialize the I/O pins as outputs
      // iterate over the pins:
      for (int thisPin = 0; thisPin < 8; thisPin++) {
      // initialize the output pins:
      pinMode(col[thisPin], OUTPUT);
      pinMode(row[thisPin], OUTPUT);
      // take the col pins (i.e. the cathodes) high to ensure that
      // the LEDS are off:
      digitalWrite(col[thisPin], HIGH);
      }

      setupScreen();

      }

      void loop() {

      // draw the screen:
      refreshScreen();

      if(count-- == 0){
      count = 500;
      if(posX--==0){
      posX = 7;
      if(posY--==0){
      posY = 7;
      bg = !bg;
      }
      }
      setupScreen();

      }
      }

      void setupScreen(){
      if(bg){
      //ON all others
      for (int x = 0; x < 8; x++) {
      for (int y = 0; y < 8; y++) {
      pixels[x][y] = LOW;
      }
      }

      //OFF current pos
      pixels[posX][posY] = HIGH;
      }else{
      //OFF all others
      for (int x = 0; x < 8; x++) {
      for (int y = 0; y < 8; y++) {
      pixels[x][y] = HIGH;
      }
      }

      //ON current pos
      pixels[posX][posY] = LOW;
      }
      }

      void refreshScreen() {
      // iterate over the rows (anodes):
      for (int thisRow = 0; thisRow < 8; thisRow++) {
      // take the row pin (anode) high:
      digitalWrite(row[thisRow], HIGH);
      // iterate over the cols (cathodes):
      for (int thisCol = 0; thisCol < 8; thisCol++) {
      // get the state of the current pixel;
      int thisPixel = pixels[thisRow][thisCol];
      // when the row is HIGH and the col is LOW,
      // the LED where they meet turns on:
      digitalWrite(col[thisCol], thisPixel);
      // turn the pixel off:
      if (thisPixel == LOW) {
      digitalWrite(col[thisCol], HIGH);
      }
      }
      // take the row pin low to turn off the whole row:
      digitalWrite(row[thisRow], LOW);
      }
      }

      Delete