Here a picture of the display and the test code. For the new guys or to the one who are not familiar with the MAX7219. This info came from the datasheet. http://www.datasheetcatalog.org/datasheet/maxim/MAX7219-MAX7221.pdf
const byte datapin = 12;
const byte latchpin = 11;
const byte clockpin = 10;
void setup()
{
pinMode(datapin, OUTPUT);
pinMode(latchpin, OUTPUT);
pinMode(clockpin, OUTPUT);
// set : Normal Mode
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 0x0C );
shiftOut(datapin, clockpin, MSBFIRST, 0x01 );
digitalWrite(latchpin, HIGH);
delay(5);
// set : Normal Operation
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 0x0F );
shiftOut(datapin, clockpin, MSBFIRST, 0x00 );
digitalWrite(latchpin, HIGH);
delay(5);
// set : Intensity
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 0x0A );
shiftOut(datapin, clockpin, MSBFIRST, 0x0B );
digitalWrite(latchpin, HIGH);
delay(5);
// set : Numbers of digits
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 0x0B );
shiftOut(datapin, clockpin, MSBFIRST, 0x07 );
digitalWrite(latchpin, HIGH);
delay(5);
// set : Decode Mode Register
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 0x09 );
shiftOut(datapin, clockpin, MSBFIRST, 0xFF );
digitalWrite(latchpin, HIGH);
}
void loop()
{
byte j;
for (int i=1;i<9;i++)
{
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, i );
shiftOut(datapin, clockpin, MSBFIRST, i );
digitalWrite(latchpin, HIGH);
delay(5);
}
delay(2000);
j = 8;
for (int i=1;i<9;i++)
{
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, i );
shiftOut(datapin, clockpin, MSBFIRST, j );
digitalWrite(latchpin, HIGH);
delay(5);
j--;
}
delay(2000);
}
