Daten speichern + 16x16 RGB-LED-Matrix ansteuern

Ich habe folgenden Sketch und rot flackert:

#define  NUM_TLCS  3 // Hier Anzahl der verwendeten TLC5940 hinschreiben
#define  NUM_ROWS  16 // Anzahl der ROWS der Matrix
#define  NUM_COLUMNS 8 // An zahl der Columns der Matrix
#include "Tlc5940Mux.h"
//#define __AVR_ATmega2560__

volatile uint8_t isShifting;
uint8_t shiftRow;
                     
// SHIFT_DATA_PIN (PF0 is analog 0) = '595 SER pin
#define SHIFT_DATA_PORT PORTF
#define SHIFT_DATA_PIN  PF0
#define SHIFT_DATA_DDR  DDRF
// SHIFT_CLK_PIN (PF1 is analog 1) = '595 SRCLK
#define SHIFT_CLK_PORT  PORTF
#define SHIFT_CLK_PIN   PF1
#define SHIFT_CLK_DDR   DDRF
// '595 RCLK is hooked to tlc XLAT pin

uint16_t Led_Red;
uint16_t Led_Green;
uint16_t Led_Blue;

static inline void
shift8_595_row(uint8_t row)
{
  // the output of the '595 for the selected row should be low, all others
  // high
  //uint8_t output = ~(1 << row);
  uint8_t output = (1 << row); // Eventuell beides mal probieren
  for (uint8_t bit = 0x80; bit; bit >>= 1) {
    if (bit & output) {
      SHIFT_DATA_PORT |= _BV(SHIFT_DATA_PIN);
    } else {
      SHIFT_DATA_PORT &= ~_BV(SHIFT_DATA_PIN);
    }    
    // pulse the '595 sclk
    SHIFT_CLK_PORT |= _BV(SHIFT_CLK_PIN);
    SHIFT_CLK_PORT &= ~_BV(SHIFT_CLK_PIN);
  }
}

ISR(TIMER1_OVF_vect)
{
  if (!isShifting) {
    disable_XLAT_pulses();
    isShifting = 1;
    sei();
    TlcMux_shiftRow(shiftRow);
    shift8_595_row(shiftRow);
    shiftRow++;
    if (shiftRow == NUM_ROWS) {
      shiftRow = 0;
    }
    enable_XLAT_pulses();
    isShifting = 0;
  }
}


const int MatrixWidth = NUM_ROWS;
const int MatrixHeight = NUM_COLUMNS;

int PixelColor[MatrixWidth+1][MatrixHeight+1][4];


void setup()
{
  SHIFT_DATA_DDR |= _BV(SHIFT_DATA_PIN);
  SHIFT_CLK_DDR  |= _BV(SHIFT_CLK_PIN);
  TlcMux_init();
}



void loop()
{
  for(int i = 1; i <= MatrixWidth; i++)
  {
    for(int j = 1; j <= MatrixHeight; j++)
    {
      PixelColor[i][j][1] = 255;
      PixelColor[i][j][2] = 0;
      PixelColor[i][j][3] = 0; 
    }
  }
  Render();
  delay(1000);
}



void Render()
{
  Display();
}



void Display()
{
  for(int i = 1; i <= MatrixWidth; i++)
  {
    for(int j = 1; j <= MatrixHeight; j++)
    {
      Matrix_Pixel(i, j, PixelColor[i][j][1], PixelColor[i][j][2], PixelColor[i][j][3]);
    }
  }  
}



void Clear()
{
  for(int i = 1; i <= MatrixWidth; i++)
  {
    for(int j = 1; j <= MatrixHeight; j++)
    {
      PixelColor[i][j][1] = 0;
      PixelColor[i][j][2] = 0;
      PixelColor[i][j][3] = 0; 
    }
  }    
}



void Matrix_Pixel(uint8_t Row, uint8_t Column, byte Red, byte Green, byte Blue)
{   
   Row -= 1;
   Column -= 1;
   Led_Red = map(Red, 0, 255, 0, 4095);
   Led_Green = map(Green, 0, 255, 0, 4095);
   Led_Blue = map(Blue, 0, 255, 0, 4095);
   
   if(Row < 8)
   {
     TlcMux_set(Row, Column, Led_Red / 1.8);
     TlcMux_set(Row, Column+16, Led_Green);
     TlcMux_set(Row, Column+32, Led_Blue);
   }
   else
   {
     TlcMux_set(Row-8, Column+8, Led_Red / 1.8);
     TlcMux_set(Row-8, Column+8+16, Led_Green);
     TlcMux_set(Row-8, Column+8+32, Led_Blue);
   }  
   //TlcMux_set(Row, Column, Led_Green);
   //TlcMux_set(Row, Column, Led_Blue);
}

Auffällig ist auch, dass wenn Pixelfehler auftreten, sagen wir bei einer 6x3 Matrix, folgendes passiert:
xxxoox
ooxxxx
ooxxxx
Es tritt eine Art verschiebung des Pixelfehlers in die zweite Matrix ein.
Kann der "Arduino" eigentlich 2 Matrizen bewältigen, ohne ext. Spannungsversorgung?