• Arduino Uno
• 40*8 Bi-color Display 
• Max 7219 IC 
• 15k Resistor
• 47uf Capacitor
• 0.1uf Capacitor
• Veroboard
• Some Connecting Wire

Dot Matrix Display Pinout

Fig: 16 pins single color display pinout

Fig: 24 pins bi-color display pinout

Max7219 Pinout

Fig: Max 7219 Pin configuration

Circuit Schematic

The circuit diagram of the led matrix display and Arduino interfacing below:-

Fig: Arduino and led matrix display interfacing

Circuit description

Source Code

 #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_KeySwitch.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 MAX_DEVICES 5  
 #define CLK_PIN  13  
 #define DATA_PIN 11  
 #define CS_PIN  10  
   
 // HARDWARE SPI  
 MD_Parola P = MD_Parola(CS_PIN, MAX_DEVICES);  
 // SOFTWARE SPI  
 //MD_Parola P = MD_Parola(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 = 40;  // 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     75  
 char curMessage[BUF_SIZE];  
 char newMessage[BUF_SIZE];  
 bool newMessageAvailable = false;  
   
 #if USE_UI_CONTROL  
   
 MD_KeySwitch uiDirection(DIRECTION_SET);  
 MD_KeySwitch 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_KeySwitch::KS_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_KeySwitch::KS_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(57600);  
  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.displayClear();  
  P.displaySuspend(false);  
   
  P.displayText(curMessage, scrollAlign, scrollSpeed, scrollPause, scrollEffect, scrollEffect);  
   
  strcpy(curMessage, "Bionics Robotics and Computation");  
  newMessage[0] = '\0';  
 }  
   
 void loop()  
 {  
 #if USE_UI_CONTROL  
  doUI();  
 #endif // USE_UI_CONTROL  
   
  readSerial();  
  if (P.displayAnimate())  
  {  
   if (newMessageAvailable)  
   {  
    strcpy(curMessage, newMessage);  
    newMessageAvailable = false;  
   }  
   P.displayReset();  
  }  
 }  

 #include <MD_Parola.h>  
 #include <MD_MAX72xx.h>  
 #include <SPI.h>  
   
 // 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 MAX_DEVICES 4  
 #define CLK_PIN  13  
 #define DATA_PIN 11  
 #define CS_PIN  10  
   
 // Hardware SPI connection  
 MD_Parola P = MD_Parola(CS_PIN, MAX_DEVICES);  
 // Arbitrary output pins  
 // MD_Parola P = MD_Parola(DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES)  
   
 #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))  
   
 // Global data  
 typedef struct  
 {  
  textEffect_t effect;  // text effect to display  
  char *    psz;   // text string nul terminated  
  uint16_t   speed;  // speed multiplier of library default  
  uint16_t   pause;  // pause multiplier for library default  
 } sCatalog;  
   
 sCatalog catalog[] =  
 {  
  { PA_PRINT, "PRINT", 1, 1 },  
  { PA_SLICE, "SLICE", 1, 1 },  
  { PA_MESH, "MESH", 20, 1 },  
  { PA_FADE, "FADE", 20, 1 },  
  { PA_WIPE, "WIPE", 5, 1 },  
  { PA_WIPE_CURSOR, "WPE_C", 4, 1 },  
  { PA_OPENING, "OPEN", 3, 1 },  
  { PA_OPENING_CURSOR, "OPN_C", 4, 1 },  
  { PA_CLOSING, "CLOSE", 3, 1 },  
  { PA_CLOSING_CURSOR, "CLS_C", 4, 1 },  
  { PA_RANDOM, "RAND", 3, 1 },  
  { PA_BLINDS, "BLIND", 7, 1 },  
  { PA_DISSOLVE, "DSLVE", 7, 1 },  
  { PA_SCROLL_UP, "SC_U", 5, 1 },  
  { PA_SCROLL_DOWN, "SC_D", 5, 1 },  
  { PA_SCROLL_LEFT, "SC_L", 5, 1 },  
  { PA_SCROLL_RIGHT, "SC_R", 5, 1 },  
  { PA_SCROLL_UP_LEFT, "SC_UL", 7, 1 },  
  { PA_SCROLL_UP_RIGHT, "SC_UR", 7, 1 },  
  { PA_SCROLL_DOWN_LEFT, "SC_DL", 7, 1 },  
  { PA_SCROLL_DOWN_RIGHT, "SC_DR", 7, 1 },  
  { PA_SCAN_HORIZ, "SCANH", 4, 1 },  
  { PA_SCAN_VERT, "SCANV", 3, 1 },  
  { PA_GROW_UP, "GRW_U", 7, 1 },  
  { PA_GROW_DOWN, "GRW_D", 7, 1 },  
 };  
   
   
 void setup(void)  
 {  
  P.begin();  
  P.setInvert(false);  
   
  for (uint8_t i=0; i<ARRAY_SIZE(catalog); i++)  
  {  
   catalog[i].speed *= P.getSpeed();  
   catalog[i].pause *= 500;  
  }  
 }  
   
 void loop(void)  
 {  
  for (uint8_t j=0; j<3; j++)  
  {  
   textPosition_t just;  
   
   switch (j)  
   {  
   case 0: just = PA_LEFT;  break;  
   case 1: just = PA_CENTER; break;  
   case 2: just = PA_RIGHT;  break;  
   }  
   
   for (uint8_t i=0; i<ARRAY_SIZE(catalog); i++)  
   {  
    P.displayText(catalog[i].psz, just, catalog[i].speed, catalog[i].pause, catalog[i].effect, catalog[i].effect);  
   
    while (!P.displayAnimate())  
     ; // animates and returns true when an animation is completed  
   
    delay(catalog[i].pause);  
   }  
  }  
 }  

• Arduino Uno.
• 4*4 keypad.
• Three 4.7k resistors.
• Four 1k resistors.
• One 220ohm resistor.
• LCD display.
• 10k potentiometer.
• Some jumper wire.

  Fig:1.1

Fig 3.1: One wire keypad with Arduino

Circuit Description

• Arduino Uno
• Micro SD card Adapter
• Micro SD card
• Card Reader
• Speaker with 3.5mm jack output
• Some Jumper wire

Convert Audio to .wav Format

If you want to play any audio file with Arduino you must need to convert the audio in wav format because Arduino can play through SD card module an audio file in a specific format. Now follow the below procedure to convert an audio file in wav format.

1. Go to the link: https://audio.online-convert.com/convert-to-wav 
2. Upload your audio you want to convert to WAV
3. Set bit resolution: " 8bit ".
4. Change sampling rate: " 16000Hz ".
5. Fixed audio channels: " mono ".

Next click on "Convert file" and download the file.

Circuit Schematic

The circuit schematic of audio player given below:-

Circuit Diagram

Circuit Description

SD card module has six pins whose Vcc and GND pin will connect with arduino 5V and GND pin respectively. Next comes to MISO, MOSI and SCK pin which use for SPI communication with arduino. These pin will connect with arduino digital pin 12 , 11 and 13 respectively. Last one CS pin will connect to digital pin 10.

3.5mm Jack

After that arduino digital pin 9 will connect to sleeve end of the speaker 3.5mm jack. Tip end of the speaker jack will go to the ground pin of the Arduino.

Source Code

The source code given below:-

You can download the library here: https://github.com/TMRh20/TMRpcm