MULTIPLEXING

hello there! I am trying to build a 8x72 large scrolling led board using the MD_Parola library. I am using 5mm leds at a separate distance of 3.5cm. I am using arduino uno and a series of 9 Maxim 7219CNG each chip with a 10uf/25v eleectrolytic capacitor and a 100nf ceramc capacitor in parallel with the voltage input i have also put a 10k 1/2W resistor at the iset pin of each chip. The project works nice for only 8 matrices but the 9th on remains either off or all leds lights on even when i define 9 devices on the program code. What could be the problem. Also sometimes some matrices just lits all the leds rather than printing the text. Help please

Could you post your properly formatted code in code tags so ‘we’ can have a looks-see?

Also a schemo would be great.

Can you swap chips or 8x8 modules around, to see if a particular chip or module has a fault.

Idahowalker:
Could you post your properly formatted code in code tags so ‘we’ can have a looks-see?

Also a schemo would be great.

#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>

// set to 1 if we are implementing the user interface pot, switch, etc
#define USE_UI_CONTROL 0

#if USE_UI_CONTROL
#include <MD_UISwitch.h>
#endif

// Turn on debug statements to the serial output
#define DEBUG 0

#if DEBUG
#define PRINT(s, x) { Serial.print(F(s)); Serial.print(x); }
#define PRINTS(x) Serial.print(F(x))
#define PRINTX(x) Serial.println(x, HEX)
#else
#define PRINT(s, x)
#define PRINTS(x)
#define PRINTX(x)
#endif

// Define the number of devices we have in the chain and the hardware interface
// NOTE: These pin numbers will probably not work with your hardware and may
// need to be adapted
#define HARDWARE_TYPE MD_MAX72XX::PAROLA_HW
#define MAX_DEVICES 9
#define CLK_PIN 13
#define DATA_PIN 11
#define CS_PIN 10

// HARDWARE SPI
MD_Parola P = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);
// SOFTWARE SPI
//MD_Parola P = MD_Parola(HARDWARE_TYPE, DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES);

// Scrolling parameters
#if USE_UI_CONTROL
const uint8_t SPEED_IN = A5;
const uint8_t DIRECTION_SET = 8; // change the effect
const uint8_t INVERT_SET = 9; // change the invert

const uint8_t SPEED_DEADBAND = 5;
#endif // USE_UI_CONTROL

uint8_t scrollSpeed = 110; // default frame delay value
textEffect_t scrollEffect = PA_SCROLL_LEFT;
textPosition_t scrollAlign = PA_LEFT;
uint16_t scrollPause = 0; // in milliseconds

// Global message buffers shared by Serial and Scrolling functions
#define BUF_SIZE 550
char curMessage[BUF_SIZE] = { “” };
char newMessage[BUF_SIZE] = {“WELCOME TO DESIRE HOTEL” };
bool newMessageAvailable = true;

#if USE_UI_CONTROL

MD_UISwitch_Digital uiDirection(DIRECTION_SET);
MD_UISwitch_Digital uiInvert(INVERT_SET);

void doUI(void)
{
// set the speed if it has changed
{
int16_t speed = map(analogRead(SPEED_IN), 0, 1023, 10, 150);

if ((speed >= ((int16_t)P.getSpeed() + SPEED_DEADBAND)) ||
(speed <= ((int16_t)P.getSpeed() - SPEED_DEADBAND)))
{
P.setSpeed(speed);
scrollSpeed = speed;
PRINT("\nChanged speed to ", P.getSpeed());
}
}

if (uiDirection.read() == MD_UISwitch::KEY_PRESS) // SCROLL DIRECTION
{
PRINTS("\nChanging scroll direction");
scrollEffect = (scrollEffect == PA_SCROLL_LEFT ? PA_SCROLL_RIGHT : PA_SCROLL_LEFT);
P.setTextEffect(scrollEffect, scrollEffect);
P.displayClear();
P.displayReset();
}

if (uiInvert.read() == MD_UISwitch::KEY_PRESS) // INVERT MODE
{
PRINTS("\nChanging invert mode");
P.setInvert(!P.getInvert());
}
}
#endif // USE_UI_CONTROL

void readSerial(void)
{
static char *cp = newMessage;

while (Serial.available())
{
*cp = (char)Serial.read();
if ((*cp == ‘\n’) || (cp - newMessage >= BUF_SIZE-2)) // end of message character or full buffer
{
*cp = ‘\0’; // end the string
// restart the index for next filling spree and flag we have a message waiting
cp = newMessage;
newMessageAvailable = true;
}
else // move char pointer to next position
cp++;
}
}

void setup()
{
Serial.begin(9600);
Serial.print("\n[Parola Scrolling Display]\nType a message for the scrolling display\nEnd message line with a newline");

#if USE_UI_CONTROL
uiDirection.begin();
uiInvert.begin();
pinMode(SPEED_IN, INPUT);

doUI();
#endif // USE_UI_CONTROL

P.begin();
P.displayText(curMessage, scrollAlign, scrollSpeed, scrollPause, scrollEffect, scrollEffect);
}

void loop()
{
#if USE_UI_CONTROL
doUI();
#endif // USE_UI_CONTROL

if (P.displayAnimate())
{
if (newMessageAvailable)
{
strcpy(curMessage, newMessage);
newMessageAvailable = false;
}
P.displayReset();
}
readSerial();
}

LEWISMURIMI:
#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>

// set to 1 if we are implementing the user interface pot, switch, etc
#define USE_UI_CONTROL 0

#if USE_UI_CONTROL
#include <MD_UISwitch.h>
#endif

// Turn on debug statements to the serial output
#define DEBUG 0

#if DEBUG
#define PRINT(s, x) { Serial.print(F(s)); Serial.print(x); }
#define PRINTS(x) Serial.print(F(x))
#define PRINTX(x) Serial.println(x, HEX)
#else
#define PRINT(s, x)
#define PRINTS(x)
#define PRINTX(x)
#endif

// Define the number of devices we have in the chain and the hardware interface
// NOTE: These pin numbers will probably not work with your hardware and may
// need to be adapted
#define HARDWARE_TYPE MD_MAX72XX::PAROLA_HW
#define MAX_DEVICES 9
#define CLK_PIN 13
#define DATA_PIN 11
#define CS_PIN 10

// HARDWARE SPI
MD_Parola P = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);
// SOFTWARE SPI
//MD_Parola P = MD_Parola(HARDWARE_TYPE, DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES);

// Scrolling parameters
#if USE_UI_CONTROL
const uint8_t SPEED_IN = A5;
const uint8_t DIRECTION_SET = 8; // change the effect
const uint8_t INVERT_SET = 9; // change the invert

const uint8_t SPEED_DEADBAND = 5;
#endif // USE_UI_CONTROL

uint8_t scrollSpeed = 110; // default frame delay value
textEffect_t scrollEffect = PA_SCROLL_LEFT;
textPosition_t scrollAlign = PA_LEFT;
uint16_t scrollPause = 0; // in milliseconds

// Global message buffers shared by Serial and Scrolling functions
#define BUF_SIZE 550
char curMessage[BUF_SIZE] = { “” };
char newMessage[BUF_SIZE] = {“WELCOME TO DESIRE HOTEL” };
bool newMessageAvailable = true;

#if USE_UI_CONTROL

MD_UISwitch_Digital uiDirection(DIRECTION_SET);
MD_UISwitch_Digital uiInvert(INVERT_SET);

void doUI(void)
{
// set the speed if it has changed
{
int16_t speed = map(analogRead(SPEED_IN), 0, 1023, 10, 150);

if ((speed >= ((int16_t)P.getSpeed() + SPEED_DEADBAND)) ||
(speed <= ((int16_t)P.getSpeed() - SPEED_DEADBAND)))
{
P.setSpeed(speed);
scrollSpeed = speed;
PRINT("\nChanged speed to ", P.getSpeed());
}
}

if (uiDirection.read() == MD_UISwitch::KEY_PRESS) // SCROLL DIRECTION
{
PRINTS("\nChanging scroll direction");
scrollEffect = (scrollEffect == PA_SCROLL_LEFT ? PA_SCROLL_RIGHT : PA_SCROLL_LEFT);
P.setTextEffect(scrollEffect, scrollEffect);
P.displayClear();
P.displayReset();
}

if (uiInvert.read() == MD_UISwitch::KEY_PRESS) // INVERT MODE
{
PRINTS("\nChanging invert mode");
P.setInvert(!P.getInvert());
}
}
#endif // USE_UI_CONTROL

void readSerial(void)
{
static char *cp = newMessage;

while (Serial.available())
{
*cp = (char)Serial.read();
if ((*cp == ‘\n’) || (cp - newMessage >= BUF_SIZE-2)) // end of message character or full buffer
{
*cp = ‘\0’; // end the string
// restart the index for next filling spree and flag we have a message waiting
cp = newMessage;
newMessageAvailable = true;
}
else // move char pointer to next position
cp++;
}
}

void setup()
{
Serial.begin(9600);
Serial.print("\n[Parola Scrolling Display]\nType a message for the scrolling display\nEnd message line with a newline");

#if USE_UI_CONTROL
uiDirection.begin();
uiInvert.begin();
pinMode(SPEED_IN, INPUT);

doUI();
#endif // USE_UI_CONTROL

P.begin();
P.displayText(curMessage, scrollAlign, scrollSpeed, scrollPause, scrollEffect, scrollEffect);
}

void loop()
{
#if USE_UI_CONTROL
doUI();
#endif // USE_UI_CONTROL

if (P.displayAnimate())
{
if (newMessageAvailable)
{
strcpy(curMessage, newMessage);
newMessageAvailable = false;
}
P.displayReset();
}
readSerial();
}

I am using the MD_MAX72XX LIBRARY FROM https://github.com

This is my entire project all the 9 matrices

Single 8x8m matrix

Code in code tags, which makes it real easy to copy and paste.

#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>

// set to 1 if we are implementing the user interface pot, switch, etc
#define USE_UI_CONTROL 0

#if USE_UI_CONTROL
#include <MD_UISwitch.h>
#endif

// Turn on debug statements to the serial output
#define DEBUG 0

#if DEBUG
#define PRINT(s, x) { Serial.print(F(s)); Serial.print(x); }
#define PRINTS(x) Serial.print(F(x))
#define PRINTX(x) Serial.println(x, HEX)
#else
#define PRINT(s, x)
#define PRINTS(x)
#define PRINTX(x)
#endif

// Define the number of devices we have in the chain and the hardware interface
// NOTE: These pin numbers will probably not work with your hardware and may
// need to be adapted
#define HARDWARE_TYPE MD_MAX72XX::PAROLA_HW
#define MAX_DEVICES 9
#define CLK_PIN   13
#define DATA_PIN  11
#define CS_PIN    10

// HARDWARE SPI
MD_Parola P = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);
// SOFTWARE SPI
//MD_Parola P = MD_Parola(HARDWARE_TYPE, DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES);

// Scrolling parameters
#if USE_UI_CONTROL
const uint8_t SPEED_IN = A5;
const uint8_t DIRECTION_SET = 8;  // change the effect
const uint8_t INVERT_SET = 9;     // change the invert

const uint8_t SPEED_DEADBAND = 5;
#endif // USE_UI_CONTROL

uint8_t scrollSpeed = 110;    // default frame delay value
textEffect_t scrollEffect = PA_SCROLL_LEFT;
textPosition_t scrollAlign = PA_LEFT;
uint16_t scrollPause = 0; // in milliseconds

// Global message buffers shared by Serial and Scrolling functions
#define  BUF_SIZE  550
char curMessage[BUF_SIZE] = { "" };
char newMessage[BUF_SIZE] = {"WELCOME TO DESIRE HOTEL" };
bool newMessageAvailable = true;

#if USE_UI_CONTROL

MD_UISwitch_Digital uiDirection(DIRECTION_SET);
MD_UISwitch_Digital uiInvert(INVERT_SET);

void doUI(void)
{
  // set the speed if it has changed
  {
    int16_t speed = map(analogRead(SPEED_IN), 0, 1023, 10, 150);

    if ((speed >= ((int16_t)P.getSpeed() + SPEED_DEADBAND)) ||
      (speed <= ((int16_t)P.getSpeed() - SPEED_DEADBAND)))
    {
      P.setSpeed(speed);
      scrollSpeed = speed;
      PRINT("\nChanged speed to ", P.getSpeed());
    }
  }

  if (uiDirection.read() == MD_UISwitch::KEY_PRESS) // SCROLL DIRECTION
  {
    PRINTS("\nChanging scroll direction");
    scrollEffect = (scrollEffect == PA_SCROLL_LEFT ? PA_SCROLL_RIGHT : PA_SCROLL_LEFT);
    P.setTextEffect(scrollEffect, scrollEffect);
    P.displayClear();
    P.displayReset();
  }

  if (uiInvert.read() == MD_UISwitch::KEY_PRESS)  // INVERT MODE
  {
    PRINTS("\nChanging invert mode");
    P.setInvert(!P.getInvert());
  }
}
#endif // USE_UI_CONTROL

void readSerial(void)
{
  static char *cp = newMessage;

  while (Serial.available())
  {
    *cp = (char)Serial.read();
    if ((*cp == '\n') || (cp - newMessage >= BUF_SIZE-2)) // end of message character or full buffer
    {
      *cp = '\0'; // end the string
      // restart the index for next filling spree and flag we have a message waiting
      cp = newMessage;
      newMessageAvailable = true;
    }
    else  // move char pointer to next position
      cp++;
  }
}

void setup()
{
  Serial.begin(9600);
  Serial.print("\n[Parola Scrolling Display]\nType a message for the scrolling display\nEnd message line with a newline");

#if USE_UI_CONTROL
  uiDirection.begin();
  uiInvert.begin();
  pinMode(SPEED_IN, INPUT);

  doUI();
#endif // USE_UI_CONTROL

  P.begin();
  P.displayText(curMessage, scrollAlign, scrollSpeed, scrollPause, scrollEffect, scrollEffect);
}

void loop()
{
#if USE_UI_CONTROL
  doUI();
#endif // USE_UI_CONTROL

  if (P.displayAnimate())
  {
    if (newMessageAvailable)
    {
      strcpy(curMessage, newMessage);
      newMessageAvailable = false;
    }
    P.displayReset();
  }
  readSerial();
}

Did you do as was suggested in reply #3? What were your results?

You need a 0.1uF ceramic capacitor on each and every chip you use.

Is there any difference in the two photographs you posted in reply #6?

In reply #1, you were asked for a schematic, but you have yet to post any.