shift register problems

I’ve been working on a 5*5 RGB led matrix project. It uses shift registers to control the anodes of the common cathode leds. It’s been displaying the right patterns for a while, but recently it suddenly stopped working. I’ve tested the connections with a multimeter, but I still can’t find the issue. It displays the right pattern once in a while, but most of the time it displays random colors on random pixels. This is the code:

/*
  ShiftRegister74HC595 - Library for simplified control of 74HC595 shift registers.
  Created by Timo Denk (www.timodenk.com), Nov 2014.
  Additional information is available at http://shiftregister.simsso.de/
  Released into the public domain.
*/

#include <ShiftRegister74HC595.h>

// create a global shift register object
// parameters: (number of shift registers, data pin, clock pin, latch pin)
ShiftRegister74HC595 sr (3, 8, 10, 9); 

//latch = 9, 
//ShiftRegister74HC595 sr (3, 10, 8, 9); 

const int cathodes[] = {2,3,4,5,6};


//const int reds[] = {1,0,7,14,13};
//const int greens[] = {15,22,21,20,19};
//const int blues[] = {12,11,10,9,8};

const int reds[] = {6,7,0,9,10};
const int greens[] = {8,17,18,19,20};
const int blues[] = {11,12,13,14,15};

boolean matrix_red_Values [] {
  1, 1, 1, 1, 1, 
  1, 0, 0, 0, 1,
  1, 0, 1, 0, 1,
  1, 0, 0, 0, 1, 
  1, 1, 1, 1, 1
};
boolean matrix_green_Values [] {
  0, 1, 1, 1, 1, 
  1, 1, 1, 1, 1,
  1, 1, 1, 1, 1,
  0, 1, 1, 1, 1, 
  0, 1, 1, 1, 1
};
boolean matrix_blue_Values [] {
  1, 1, 1, 1, 1, 
  1, 1, 1, 1, 1,
  1, 1, 0, 1, 1,
  1, 1, 1, 1, 1, 
  1, 1, 1, 1, 1
};

void setup() { 
  Serial.begin(9600);
  for(int x=0; x<5; x++)
    pinMode(cathodes[x], OUTPUT);
    
}

void loop() {
  
  
 for(int cathodeCycle = 0; cathodeCycle < 5; cathodeCycle++){
   digitalWrite(cathodes[cathodeCycle], LOW);
   digitalWrite(cathodes[cathodeCycle-1], HIGH);
    
   for(int x = 0; x < 5; x++){
      sr.set(reds[x], matrix_red_Values[(cathodeCycle * 5)+ x] ); 
      //delay(1);
    //  for(int y = 0; y < 5; y++)       
   //    sr.set(reds[y], LOW); 
        
      sr.set(greens[x], matrix_green_Values[(cathodeCycle * 5)+ x] ); 
      //delay(1);
    //  for(int y = 0; y < 5; y++)       
    //    sr.set(greens[y], LOW); 
        
      sr.set(blues[x], matrix_blue_Values[(cathodeCycle * 5)+ x] ); 
     // delay(1);
    //  for(int y = 0; y < 5; y++)       
    //    sr.set(blues[y], LOW); 

    // delay(100);
     sr.setAllLow();
     //Serial.println(millis());
        
   }
   //delay(100);
    // sr.setAllLow();
 }
 digitalWrite(cathodes[4], HIGH);


}

The schematic is attached

led matrix.pdf (28.6 KB)

[led matrix.pdf (28.6 KB)](https://forum.arduino.cc/index.php?action=dlattach;topic=611192.0;attach=304703)

Hmm, no other takers? Albeit only six hours.

Well, that schematic is a horrible mess!

Seriously - two Nanos which apparently must work in synchrony to produce a display? :astonished: And you gave the code for only one? :astonished:

And resistors in the cathode commons? :astonished: That will not work well if you propose to simultaneously illuminate more than one of the primaries at a time.

This should have been done with one Nano and NeoPixels - in which case just buy an 8 by 8 array and use that.
Or maybe this one:

You are using chips - the 74HC595s and the Nanos which are not suitable for directly multiplexing displays - and then you want to implement the multiplexing in software! :roll_eyes:

As you already have the LEDs, let's see. A MAX7219 can drive two rows of RGB LEDs by eight columns.You want five columns so you have three left over. A second MAX7219 can drive another two rows of RGB LEDs and the six left-over columns can be used to fill in the fifth row with a number still left over.

So two MAX7219s - you can use the crude modules available and ignore the red matrices provided - would do the job properly with only the two control resistors in the two MAX7219s and some capacitors. You would have to code for the odd arrangement - but it is worse in your present design anyway, and with the MAX7219s you do not have to worry about the multiplexing at all. :grinning:

I suspect you have burnt out something - likely one of the 74HC595s.

OTOH, surely you are not silly enough to try and power from the "Raw" pin?

I have not seen a Nano with a "5.5V" pin either. :astonished: