Hello
There are multiple ways.... (as usual)
There are these chips from Maxim called MAX7219 that can drive up to 8x8 leds matrices. They are very simple to wire up, you just need a resistor and a capacitor. in the arduino distribution there should be some code called MAX7219 (written by Nick Zambetti) that shows how to send data to these guys.
you can find a schematic here in the datasheet http://pdfserv.maxim-ic.com/en/ds/MAX7219-MAX7221.pdf
this can drive even fairly bright LEDs.
I'll attach the code here.
// define arduino pins
byte pin_max7219_dataIn = 2;
byte pin_max7219_clock = 3;
byte pin_max7219_load = 4;
// specify wiring pin i/o directions
void setPinModes()
{
pinMode(pin_max7219_dataIn, OUTPUT);
pinMode(pin_max7219_clock, OUTPUT);
pinMode(pin_max7219_load, OUTPUT);
}
// define max7219 registers
byte max7219_reg_noop = 0x00;
byte max7219_reg_digit0 = 0x01;
byte max7219_reg_digit1 = 0x02;
byte max7219_reg_digit2 = 0x03;
byte max7219_reg_digit3 = 0x04;
byte max7219_reg_digit4 = 0x05;
byte max7219_reg_digit5 = 0x06;
byte max7219_reg_digit6 = 0x07;
byte max7219_reg_digit7 = 0x08;
byte max7219_reg_decodeMode = 0x09;
byte max7219_reg_intensity = 0x0a;
byte max7219_reg_scanLimit = 0x0b;
byte max7219_reg_shutdown = 0x0c;
byte max7219_reg_displayTest = 0x0f;
// define max7219 as rows and cols (for nexus 8x8 displays)
byte max7219_row0 = 0x01;
byte max7219_row1 = 0x02;
byte max7219_row2 = 0x03;
byte max7219_row3 = 0x04;
byte max7219_row4 = 0x05;
byte max7219_row5 = 0x06;
byte max7219_row6 = 0x07;
byte max7219_row7 = 0x08;
byte max7219_col0 = 0x01;
byte max7219_col1 = 0x02;
byte max7219_col2 = 0x04;
byte max7219_col3 = 0x08;
byte max7219_col4 = 0x10;
byte max7219_col5 = 0x20;
byte max7219_col6 = 0x40;
byte max7219_col7 = 0x80;
// function to control max7219 data line
void max7219_setData(boolean value)
{
digitalWrite(pin_max7219_dataIn, value);
}
// function to control max7219 clock line
void max7219_setClock(boolean value)
{
digitalWrite(pin_max7219_clock, value);
}
// function to control max7219 load line
void max7219_setLoad(boolean value)
{
digitalWrite(pin_max7219_load, value);
}
// function that puts a byte of data to the max7219
void max7219_putByte(byte data)
{
byte i = 8;
byte mask;
while(i > 0) {
mask = 0x01 << (i - 1); // get bitmask
max7219_setClock(LOW); // tick
if (data & mask){ // choose bit
max7219_setData(HIGH); // send 1
}
else{
max7219_setData(LOW); // send 0
}
max7219_setClock(HIGH); // tock
--i; // move to lesser bit
}
}
// function that puts a byte of data into a max7219 register
void max7219_put(byte reg, byte data)
{
max7219_setLoad(LOW); // begin
max7219_putByte(reg); // specify register
max7219_putByte(data); // put data
max7219_setLoad(LOW); // latch in data
max7219_setLoad(HIGH); // end
max7219_setClock(LOW); // tick
}
// function that sets brightness of the max7219
void max7219_setIntensity(byte intensity)
{
// range: 0x00 to 0x0f
max7219_put(max7219_reg_intensity, intensity & 0x0f);
}
// function that sets the same value for all registers of the max7219
void max7219_all(byte value){
max7219_put(0x01, value);
max7219_put(0x02, value);
max7219_put(0x03, value);
max7219_put(0x04, value);
max7219_put(0x05, value);
max7219_put(0x06, value);
max7219_put(0x07, value);
max7219_put(0x08, value);
}
// function that initializes the max7219 to use a matrix of leds
void max7219_init()
{
max7219_put(max7219_reg_scanLimit, 0x04); // use 5 columns
max7219_put(max7219_reg_decodeMode, 0x00); // using an led matrix (not digits)
max7219_put(max7219_reg_shutdown, 0x01); // not in shutdown mode
max7219_put(max7219_reg_displayTest, 0x00); // no display test
max7219_all(0x00); // empty registers
max7219_setIntensity(0x08); // set initial brightness to dim
}
// program initialization routine
void setup()
{
beginSerial(9600);
setPinModes();
max7219_init();
}
// program loop
void loop()
{
//printString("blank\n");
max7219_all(0x00);
delay(500);
// draw diagonal line
//printString("diagonal");
max7219_put(max7219_row0, 0x0f);
max7219_put(max7219_row1, 0x0e);
max7219_put(max7219_row2, 0x08);
max7219_put(max7219_row3, 0x03);
max7219_put(max7219_row4, 0x1e);
max7219_put(max7219_row5, 0x0e);
max7219_put(max7219_row6, 0x0e);
max7219_put(max7219_row7, 0x0e);
delay(500);
}
If you have more questions just ask
massimo