/* Contact Image Sensor

    Program for controlling an  from an Canon MX700 OfficeJet Printer

    Author: atzensepp 1.5.2017

CIS-Sensor-Modul Header:
  1 LED Common Anode 
  2 LED B Cathode
  3 LED G Cathode
  4 LED R Cathode
  5 GND
  6 CLK
  7 SP
  8 Mode  ??? 
  9 3.3V
  10 GND
  11 V_ref ???  ~ Voltage Divider ~ 1.2 V 
  12 Analog Out

Connection to Arduino:
Arduino Uno     CANON CIS-Sensor-Module
PC0 (A0)    (6) CLK 
PC1 (A1)    (7) SP 
PC2 (A2)        
            (11) V_ref   (voltage divider -> 1.2 V)    
PC4 (A4)    (12) Analog Out
5V  
            (8) unknown I/O signal to GND ?          
3.3V        (9)
GND         (5) (10) 
PD7         (4) via 470 Ohm 
PD6         (3) via 470 Ohm
PD5         (2) via 470 Ohm
5V          (1)
          
Connection from Analog Out to Arduino:
                3.3V
                |
                -
                10k
                _
                |
A4 ---[ 1k ]----+---------o Analog Out (12)
                |
                -
                10k
                -
                |
               GND
*/
               
int analogPin = 4;

void ADC_init(void)
{
  // choose AVcc as reference:
  ADMUX = (1<<REFS0);
  
  ADCSRA &= ~0x07;
  ADCSRA |= 0x03; 
   
  ADCSRA |= (1<<ADEN);                  // ADC aktivieren

  /* nach Aktivieren des ADC wird ein "Dummy-Readout" empfohlen, man liest
     also einen Wert und verwirft diesen, um den ADC "warmlaufen zu lassen" */

  ADCSRA |= (1<<ADSC);                  // eine ADC-Wandlung
  while (ADCSRA & (1<<ADSC) ) {         // auf Abschluss der Konvertierung warten
  }
  /* ADCW muss einmal gelesen werden, sonst wird Ergebnis der nächsten
     Wandlung nicht übernommen. */
  (void) ADCW;
}

void setup() {
  // put your setup code here, to run once:
 Serial.begin( 1000000 );


 analogReference(DEFAULT ) ;
 pinMode(A4, INPUT);
 pinMode(PD7,OUTPUT);
 pinMode(PD6,OUTPUT);
 pinMode(PD5,OUTPUT);
 
 // digitalWrite(A4, 0);
 pinMode(A0, OUTPUT);
 pinMode(A1, OUTPUT);
 digitalWrite(A0,LOW);
 digitalWrite(A1,LOW);
 
  ADC_init();
 
   ADMUX = (ADMUX & ~(0x1F)) | (4 & 0x1F);
}

void loop() {
  char buf[2];
  int cnt;
  int val;
  int emit=0;
  int eightbits=1;
  byte c;
 
  // put your main code here, to run repeatedly:
   if (Serial.available() > 0) {
        // read the incoming byte:
      c = Serial.read();
      switch(c)
      { 
        case 'S':  emit=1;  break;
        case  'R' : digitalWrite(PD7,!digitalRead(PD7)); break;
        case  'G' : digitalWrite(PD6,!digitalRead(PD6)); break;
        case  'B' : digitalWrite(PD5,!digitalRead(PD5)); break;
        case '8': 
          if(eightbits)
          {
            eightbits=0;
            Serial.write('n');
          }
          else
          {
            eightbits=1;
            Serial.write('y');
          }
          break;
      }
      
      
      digitalWrite(A1,HIGH);
      delayMicroseconds(2);
      digitalWrite(A0,HIGH);
      delayMicroseconds(2);
      digitalWrite(A0,LOW);
      delayMicroseconds(2);
      digitalWrite(A1,LOW);
      delayMicroseconds(2);
         
      for(cnt=0;cnt<5000;cnt++)
      {
        digitalWrite(A0,HIGH);
        digitalWrite(A0,LOW);
        delayMicroseconds(2);
        val = analogRead(A4);
        /*  ADMUX = (ADMUX & ~(0x1F)) | (4 & 0x1F);
        ADCSRA |= (1<<ADSC);            // eine Wandlung "single conversion"
        while (ADCSRA & (1<<ADSC) ) ;   // auf Abschluss der Konvertierung warten
        val=ADCW & 0x3ff; 
*/
        if(emit) 
        {
          Serial.write((val>>2) & 0xff);
        }
      }
      emit=0;
   }
}