The MAX7219CNG is a serial input/output display driver designed to interface microprocessors to 7-segment numeric LED displays, bar-graph displays, or individual LEDs. The chip features a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers and an 8x8 static RAM that stores each digit. It uses SPI for communication and allows individual digits to be addressed and updated without rewriting the entire display. The IC includes a single external resistor to set the segment current for all LEDs, a low-power shutdown mode, analog and digital brightness control, a scan limit register, and a test mode that forces all LEDs on.

 

Package Includes:

• 1 x MAX7219 Serial Input/Output Display Driver IC

 

Features:

• Serial Input/Output: The MAX7219CNG has a serial interface for communication with a microprocessor or other device, making it easy to integrate into digital systems.
• Common-Cathode: The driver is designed to drive common-cathode LED displays, including 7-segment numeric displays, bar-graph displays, or 64 individual LEDs.
• BCD Code-B Decoder: The MAX7219CNG includes an on-chip binary coded decimal (BCD) code-B decoder, which makes it easy to interface with BCD displays.
• Multiplex Scan Circuitry: The IC includes multiplex scan circuitry that can drive up to eight digits.
• Segment and Digit Drivers: The MAX7219CNG includes segment and digit drivers, making it easy to control the individual segments of the display.
• 8x8 Static RAM: The IC also includes an on-chip 8x8 static RAM that stores the data for each digit.
• Low Power Shutdown Mode: The MAX7219CNG has a low-power shutdown mode that reduces the current consumption to 150μA.
• Analog and Digital Brightness Control: The IC also includes both analog and digital brightness control, allowing the user to adjust the brightness of the display.
• Scan Limit Register: The MAX7219CNG has a scan limit register that allows the user to display from 1 to 8 digits.
• Test Mode: The IC includes a test mode that forces all LEDs on, making it easy to check that all segments of the display are functioning properly.

 

Description:

The MAX7219CNG is a highly integrated LED display driver that offers a compact and efficient solution for interfacing microprocessors with up to 8-digit 7-segment numeric LED displays, bar-graph displays, or 64 individual LEDs. Its on-chip BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, and 8x8 static RAM make it a powerful tool for driving various LED display applications. The MAX7219 is designed to communicate with microprocessors through the Serial Peripheral Interface (SPI), allowing for easy integration with a variety of systems. Additionally, it offers individual digit addressing and updating, enabling precise control over each digit without requiring a full rewrite of the display. One of the key features of the MAX7219 is its ability to set the segment current for all LEDs using only one external resistor, simplifying the design process and reducing the need for additional components. It also includes a low-power shutdown mode that draws only 150μA, making it ideal for battery-powered applications, as well as a both analog and digital brightness control for fine-tuning the display. Furthermore, the MAX7219 offers a scan limit register that allows the user to display from 1 to 8 digits, as well as a test mode that forces all LEDs on for debugging and testing purposes. Overall, the MAX7219CNG is a versatile and user-friendly LED display driver that can be used in a wide range of applications.

 

Principle of Work:

The MAX7219CNG operates by multiplexing the display. Each digit or segment is illuminated in sequence, and this is repeated fast enough that the human eye perceives it as a continuous display. Communication with the MAX7219CNG is achieved through SPI (Serial Peripheral Interface) protocol, which allows for high-speed data transfer between the microcontroller and the MAX7219CNG. The IC contains an on-chip 8x8 static RAM, which stores the data for each digit. This means that each digit can be addressed and updated individually, without having to rewrite the entire display. The MAX7219CNG includes a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, as well as analog and digital brightness control. The scan limit register allows the user to display from 1 to 8 digits, and a test mode that forces all LEDs on, making it easy to verify the functionality of the display. The MAX7219CNG also includes a low-power shutdown mode, which reduces power consumption to 150μA when not in use.

 

Pinout of the Module:

 

• V+ - Power supply voltage input (4V to 5.5V)
• GND - Ground reference
• DIN - Serial data input
• CS - Chip select input
• CLK - Serial clock input
• DOUT - Serial data output (for daisy-chaining multiple MAX7219s)
• LOAD - Load signal input, used to latch data into internal registers
• DIG0-DIG7 - Segment driver outputs for 7-segment displays or LEDs (up to 64)
• DP - Decimal point segment driver output, used to control the decimal point of a 7-segment display
• ISET - Current set input, used to set the segment current for all LEDs (requires an external resistor)
• BI/RBO - Blank input/ripple blank output, used to blank all displays or to daisy-chain multiple MAX7219s

Note: Pins DIG0-DIG7 are segmented driver outputs, and the LED segments should be connected between these pins and the V+ supply through a current-limiting resistor. The segment current is set by an external resistor connected to the ISET pin. The MAX7219 can be cascaded to drive larger displays or more LEDs by connecting the DOUT pin of one device to the DIN pin of the next device. The LOAD pin is used to latch data into the MAX7219's internal registers. When LOAD goes low, the data on DIN is transferred to the corresponding register, and when LOAD goes high again, the MAX7219 starts scanning the display. The CS pin is used to select the MAX7219 for communication.

 

Applications:

1. Digital clocks and timers
2. Scoreboards and game displays
3. Temperature and humidity displays
4. Audio level displays
5. Voltage and current meters
6. Industrial control panels
7. Signage displays
8. Advertising displays

 

Circuit: 

 

• This circuit is a digital clock that uses an Arduino, 7-segment displays, and a MAX7219 IC. The clock displays the current time and allows users to set or reset the time. To create this clock.
• the following components are required:
  • 7-segments x6
  • Arduino UNO x1
  • MAX7219 IC x1
  • Push buttons x3
  • Breadboard x1
  • Jumper wires or connecting wires

• The digital clock is based on the MAX7219 IC-based 7-segment driver module, which is an 8-digit common-cathode LED display driver. The data pins of the 7 segments are connected to SEG A to SEG G and DP pins of MAX7219. The common-cathode terminals of the segments are connected to the DIG0 to DIG7 pins of MAX7219. Pins 4 and 9 of the IC are hard-wired to the ground, and pin 19 is connected to the 5V terminal. Pin 18 of MAX7219 is also connected to 5V DC via a suitable resistor.
• The DIN, LOAD, and CLK pins of the MAX7219 IC are connected to the digital I/O pins of the Arduino. The DIN, LOAD, and CLK pins of the IC are connected to pins 12, 10, and 11 of the Arduino UNO, respectively. The MAX7219 module is supplied with 5V DC and ground from the Arduino itself.
• In addition to the MAX7219 IC-based 7-segment driver, three push buttons are also connected to the Arduino. These pushbuttons are interfaced at pins 0, 1, and 2 of Arduino UNO. These Arduino pins are internally pulled up. The button at pin 0 controls the mode of the clock. The button at pin 1 allows selecting seconds, minutes, and hours. The button at pin 2 increments the selected clock element, seconds, minutes, or hours. The clock is designed to be basic, using only microcontroller features to generate delays of a precise interval.

 

Library: 

No need to install any library.

 

Code:

The code is for a clock display using a 7-segment LED display. It utilizes the SPI protocol to communicate with the LED display driver, and the code includes functions for initializing the display, setting the characters to be displayed, and controlling the display to show either the current time or to allow the user to adjust the time. The clock can be switched between modes by pressing a button connected to pin 0, and the time can be adjusted by pressing a button connected to pin 2 and selecting the digit to be adjusted with a button connected to pin 1. The code also includes a lookup table for the character values to be displayed on the LED segments. 

#include "SPI.h"
int SPI_MOSI = 12;
int SPI_CLK = 11;
int SPI_CS = 10; 
byte spidata[16];
uint8_t sec = 0; 
uint8_t minute = 0; 
uint8_t hour = 12; 
uint8_t clockmode = 0; 
uint8_t select = 0; 

const static byte charTable [] PROGMEM  = {
B01111110,B00110000,B01101101,B01111001,B00110011,B01011011,B01011111,B01110000,
B01111111,B01111011,B01110111,B00011111,B01001110,B00111101,B01001111,B01000111,
};


void spiTransfer(volatile byte opcode, volatile byte data) 
{
digitalWrite(SPI_CS,LOW);
shiftOut(SPI_MOSI,SPI_CLK,MSBFIRST, opcode);
shiftOut(SPI_MOSI,SPI_CLK,MSBFIRST, data);
digitalWrite(SPI_CS,HIGH);
}


void clearDisplay()
{
for(int i=0;i<8;i++) 
{
spiTransfer(i+1,0); 
}
}


void shutdown(bool b) 
{
if(b)
spiTransfer(12,0);
else
spiTransfer(12,1);
}


void init_7seg()
{
pinMode(SPI_MOSI, OUTPUT);
pinMode(SPI_CLK, OUTPUT);
pinMode(SPI_CS, OUTPUT);
digitalWrite(SPI_CS, HIGH);
spiTransfer(15,0);
spiTransfer(11,7);
spiTransfer(9,0);
clearDisplay();
shutdown(true);
}


void setChar(int digit, char value, boolean dp)
{
byte index,v;
if(digit<0 || digit>7)
return;
index=(byte)value;
if(index >15 || index <0) {
//no defined beyond index 15
v = 0;
}
v=pgm_read_byte_near(charTable + index); 
if(dp)
v|=B10000000;
spiTransfer(digit+1,v);
}


void setup() {
init_7seg();
shutdown(false);
spiTransfer(10,8);
clearDisplay();
pinMode(0, INPUT_PULLUP); //Mode pin
pinMode(1, INPUT_PULLUP); //Select pin
pinMode(2, INPUT_PULLUP); //Increament pin
}


void loop() {
if(digitalRead(0) == LOW){
clockmode = clockmode +1; 
if(clockmode>1) clockmode =  0; 
delay(250);  
}


if(clockmode == 0){
int d0 = sec%10;
setChar(0, d0, false);
int d1 = (sec/10)%10;
setChar(1, d1, false);
int d2 = minute%10;
setChar(2, d2, true);
int d3 = (minute/10)%10;
setChar(3, d3, false);
int d4 = hour%10;
setChar(4, d4, true);
int d5 = (hour/10)%10;
setChar(5, d5, false);
delay(1000); 
sec = sec+1; 
if(sec>59){sec = 0; minute = minute +1;}
if(minute>59){minute = 0; hour = hour+1;}
if(hour>12){hour = 1; minute = 0; sec = 0;}
}

if(clockmode ==  1){
if(digitalRead(1) == LOW)
  {
  select = select +1; 
  if(select>2) select = 0; 
  delay(250);
  }
if(digitalRead(2) == LOW && select == 0){sec = sec+1; delay(250); if(sec>59)sec=0;} 
if(digitalRead(2) == LOW && select == 1){minute = minute+1; delay(250); if(minute>59)minute=0;}
if(digitalRead(2) == LOW && select == 2){hour = hour+1; delay(250); if(hour>12)hour = 1;}
int d0 = sec%10;
setChar(0, d0, false);
int d1 = (sec/10)%10;
setChar(1, d1, false);
int d2 = minute%10;
setChar(2, d2, true);
int d3 = (minute/10)%10;
setChar(3, d3, false);
int d4 = hour%10;
setChar(4, d4, true);
int d5 = (hour/10)%10;
setChar(5, d5, false);
}

}

• The code initializes the SPI pins for communication with the 7-segment display, defines variables for storing the current time and mode, and defines a lookup table for converting characters to their corresponding 7-segment display codes.
• The spiTransfer() the function is used for sending data to the 7-segment display over SPI, while clearDisplay() and shutdown() functions are used for clearing the display and turning off the display respectively.
• The setChar() the function takes a digit number, a character value, and a boolean flag for a decimal point and sets the corresponding 7-segment display segment to display the character.
• In the setup() function, the pins for the mode, select, and increment buttons are initialized with internal pull-up resistors, and the clock is set to display mode by default.
• In the loop() function, the code checks if the mode button is pressed and toggles the clock mode if it is. In display mode, the code sets the 7-segment display segments to display the current time with seconds, minutes, and hours. In set mode, the code checks which of the increment buttons is pressed and increments the corresponding time value accordingly. The current time is then displayed on the 7-segment display.

 

Technical Details: 

• Supply voltage range: 4V to 5.5V
• Output current: Up to 40mA per segment or 120mA for the entire package
• Serial interface: SPI-compatible
• Maximum SPI clock frequency: 10MHz
• Display scan limit: 1 to 8 digits
• On-chip BCD decoder
• On-chip oscillator
• Power-saving shutdown mode
• Pin-compatible with MAX7221, which is a higher-output-current version of the same driver IC.

 

Resources:

• Datasheet

 

Comparisons:

Advantages of using MAX7219:

1. Saves Arduino pins: The MAX7219 requires only three pins of the Arduino for controlling a large number of LED matrices or 7-segment displays. This leaves more pins available for other components and sensors.
2. Easy to use: The MAX7219 takes care of multiplexing and driving the LEDs, reducing the complexity of the code needed to control the displays.
3. Scalability: Using the MAX7219 makes it easy to expand the number of displays without adding complexity to the code.
4. Low power consumption: The MAX7219 uses very little power, making it ideal for battery-powered applications.

Disadvantages of using MAX7219:

1. Additional component: The MAX7219 requires an additional component, the display module, which adds to the cost and complexity of the project.
2. Limited control: The MAX7219 is designed to control only LED matrices and 7-segment displays. If you need to control other types of displays, such as LCDs, you will need to use a different driver or write your own code.

Advantages of using Arduino alone:

1. Complete control: Using the Arduino alone gives you complete control over the display, allowing you to create custom animations and effects.
2. Cost-effective: Using the Arduino alone can be more cost-effective if you already have the necessary components and do not need the scalability or low power consumption of the MAX7219.
3. Versatility: The Arduino can be programmed to control a wide range of displays, not just LED matrices and 7-segment displays.

Disadvantages of using Arduino alone:

1. Complexity: Controlling LED matrices and 7-segment displays directly with the Arduino requires more complex code and a deeper understanding of electronics.
2. Pin limitations: Using the Arduino alone can quickly use up available pins, limiting the number of displays you can control and the complexity of the project.