MAX7219 interface

The MAX7219 is a compact, serial input/output common-cathode display drivers that interface

microcontroller to 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual

LEDs. Included on-chip are a BCD code-B decoder, multiplex scan circuitry, segment and digit

drivers, and an 8x8 static RAM that stores each digit.

Only one external resistor is required to set the segment current for all LEDs. The MAX7221 is compatible

with SPI™, QSPI™, and MICROWIRE™, and has slewrate-limited segment drivers to reduce EMI.

A convenient 4-wire serial interface connects to all common ìPs. Individual digits may be addressed and

updated without rewriting the entire display. The MAX7219/MAX7221 also allow the user to select

code-B decoding or no-decode for each digit.

The devices include a 150mA low-power shutdown mode, analog and digital brightness control, a scanlimit

The Basic initialisation program comes here

void max7219_init()

{

PORTC = 0xFD; //ON MAX

SPI_write(0x09); //BCD mode

SPI_write(0xFF);

PORTC = 0x02; //OFF MAX

PORTC = 0xFD; //ON MAX

SPI_write(0x0A); //Intensity

SPI_write(0x0F);

PORTC = 0x02; //OFF MAX

PORTC = 0xFD; //ON MAX

SPI_write(0x0B); //Display refresh

SPI_write(0x07);

PORTC = 0x02; //OFF MAX

PORTC = 0xFD; //ON MAX

SPI_write(0x0C); //Turn on the display

SPI_write(0x01);

PORTC = 0x02; // OFF MAX

PORTC = 0xFD; //ON MAX

SPI_write(0x00); //NO Test

SPI_write(0xFF);

PORTC = 0x02; //OFF MAX

}

Sample Program

#include "m7219.c"

unsigned char i;

void main()

{

delay_ms(100);

SPI_init();

delay_ms(100);

TRISC &= 0xFD;

delay_ms(100);

max7219_init();

for (i = 1; i<=8; i++)

{

PORTC &= 0xFD;

SPI_write(i);

SPI_write(8-i);

delay_ms(500);

PORTC = 0x02;

}

Any PIC with Hardware SPI will work.. Now you can use up to eight 7-segment displays in your project using MAX7219. Make changes according to your project needs. Go through with datasheet of MAX7219 to get all functions.