/*
 
 http://www.bristolwatch.com/arduino/arduino_max7219a.htm
 Arduino RTC Clock with MAX7219 8-Digit LED Display
 Author: Lewis Loflin lewis@bvu.net
 http://www.bristolwatch.com

 */


#define RB5  7  // CS
#define RB6  8  // DATA
#define RB7  9  // CLK

// pattern for 8 X 8 LED matrix
char array1[] = {
  0x00, 0x00, 0x81, 0x42, 0x24, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00
};

void setup()   {

  pinMode(RB5, OUTPUT);
  pinMode(RB6, OUTPUT);
  pinMode(RB7, OUTPUT);
  digitalWrite(RB5, LOW);
}

void loop()   {
  delay(1000);
  init_MAX7219();

  int k = 0;
  while (1)   {
    for (int j = 1; j < 9; j++)   {
      writeMAX7219(j + k, array1[j]);
    }
    delay(50);
    k++;
    if (k > 8) k = 0;
  }
}

// shift data to MAX7219
// RB7 -> CLK, RB6 -> DATA, RB5 -> CS not
void ssrOut(unsigned char val)  {
  int j;
  for (j = 1; j <= 8; j++)  { // shift out MSB first
    unsigned char  temp = val & 0x80; // MSB out first
    if (temp == 0x80) digitalWrite(RB6, 1); // RB6 DATA
    else digitalWrite(RB6, 0);
    digitalWrite(RB7, 1);
    delayMicroseconds(10);
    digitalWrite(RB7, 0);
    val = val << 1; // shift one place left
  }  // next j
}

void pulseCS(void)   {
  digitalWrite(RB5, 1);
  delay(1);
  digitalWrite(RB5, 0);
}

void init_MAX7219(void)   {
  digitalWrite(RB5, 0); // CS NOT

  // set decode mode
  ssrOut(0x09);
  ssrOut(0x00); // no decode
  pulseCS();

  // set intensity
  ssrOut(0x0A);
  ssrOut(0x08); // 0 - F
  pulseCS();

  // set scan limit
  ssrOut(0x0B);
  ssrOut(0x07); // 8 digits
  pulseCS();

  // set for normal operation
  ssrOut(0x0C);
  ssrOut(0x01);
  pulseCS();
}

void writeMAX7219(char address, char data)   {
  if ((address < 1) || (address > 8)) return;
  ssrOut(address); // valid numbers 1-8
  ssrOut(data);
  pulseCS();
}