/*
 * 7221 demo
 *
 */

int din = 4;
int dout = 3;
int clk = 2;
int load = 5;

byte incoming_register = 0x00;
byte incoming_data_1 = 0x00;
byte incoming_data_2 = 0x00;

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;

void setup()
{
	pinMode(din, OUTPUT);
	pinMode(clk, OUTPUT);
	pinMode(load, OUTPUT);
	pinMode(dout, INPUT);
	
	digitalWrite(din, LOW);
	digitalWrite(clk, LOW);
	digitalWrite(load, LOW);

	Serial.begin(57600);
	
	commit(max7219_reg_scanLimit, 0x07);      
	commit(max7219_reg_decodeMode, 0x00);  // using an led matrix (not digits)
	commit(max7219_reg_shutdown, 0x01);
	commit(max7219_reg_displayTest, 0x00); // no display test
	commit(max7219_reg_intensity, 0x0F);    // the first 0x0f is the value you can set

}

void loop()
{	
	serial();
}

void serial() {
	Serial.println("What Register?");
	
	while (Serial.available() < 1) {		
		delay(200);
	}
	
	incoming_register = Serial.read()-0x30;
	if(incoming_register > 0x09) {
		incoming_register -= 0x07;
	}
	Serial.println(incoming_register, HEX);
	
	Serial.println("What data?");
	
	while(Serial.available() < 2) {
		delay(200);
	}
	
	incoming_data_1 = Serial.read()-0x30;
	if(incoming_data_1 > 0x09) {
		incoming_data_1 -= 0x07;
	}
	
	incoming_data_2 = Serial.read()-0x30;
	if(incoming_data_2 > 0x09) {
		incoming_data_2 -= 0x07;
	}
	
	byte incoming_data = incoming_data_1*16+incoming_data_2;
	Serial.println(incoming_data, HEX);
	
	if(incoming_register >= 0x00 && incoming_register < 0x10 && incoming_data >= 0x00 && incoming_data <= 0xFF) {
		Serial.println("Data is valid ... passing to chip");
		commit(incoming_register, incoming_data);
	}
	Serial.println();
}

void loadByte(byte data) {
	byte i = 8;
	byte mask;
	while(i > 0) {
		mask = 0x01 << (i - 1);
		digitalWrite(clk, LOW);
		
		if (data & mask){
			digitalWrite(din, HIGH);
		} else {
			digitalWrite(din, LOW);
		}
		
		digitalWrite(clk, HIGH);
		i--;
	}
}

void commit(byte reg, byte data) {
	digitalWrite(load, LOW);
	loadByte(reg);
	loadByte(data);
	digitalWrite(load, HIGH);
}