// Project#13 - Arduino UNO
// In this project we are going to hook up an ordinary Arudino UNO to our PC and have it control either 4x LEDs or a 4-channel relay board. 
// We'll be creating A GPI based API that toggles the states of each relay, or turn them all off.
// For this project you'll need a 4-channel relay board, or 4x LEDs with 4x current limiting resistors.
// You can use the RPI_no_RPI for this project if you'd like, but the idea is to use an off-the-shelf standard UNO
// Connections:
// Connect 5v from the UNO to the 5v supply pin of your 4-channel relay board.
// Connect GND from your UNO to the GND (ground) of your relay board.
// Connect Arduino GPIOs 2 through 5 to the rleay drive pins on the relay board
// If you're using LEDs, connect the anodes (positive) of each LED to GPIOS 2 through 5, and the cathodes (negative) to current-limiting...
// ... resistors in the area of 300-1000 ohms.  Connect the second side of the reistors to GND (ground).  That way, when the relay GPIOS...
// ... Turn on, the LEDs turn off, and when the relays turn off, the LEDs turn on.  The logic is backwards because the relays for my...
// ... relay board were active-low, which means that when the drive pins are pulled to 0v, the relay turns on, and when set to 5v...
// ... the relays turn off

#define relay1 2  // Set the relay drive GPIO pins to 2/3/4/5
#define relay2 3
#define relay3 4
#define relay4 5
byte incomingByte = 0x00;  // This byte will hold the instructions received from the PC
int relay1_state = 0;      // These four integers hold the states of the relays (off = 0, and on = 1)
int relay2_state = 0;      // All four states start off in the 0/off state
int relay3_state = 0;
int relay4_state = 0;

void setup() {   //  Let's set up comms, define the functions of the GPIO pins, and turn all relays off.
  Serial.begin(115200);      // Set the baud rate to match the PC comms baud rate (115200)
  pinMode(relay1,OUTPUT);    // Set relay1 - relay4 as outputs
  pinMode(relay2,OUTPUT);
  pinMode(relay3,OUTPUT);
  pinMode(relay4,OUTPUT);
  digitalWrite(relay1,HIGH); // Turn relays off.  If your relay is active high, change this value to LOW
  digitalWrite(relay2,HIGH);
  digitalWrite(relay3,HIGH);
  digitalWrite(relay4,HIGH);
}



void loop(){ // This is the main program loop
    while (Serial.available() > 0) {  // Do nothing until a serial instruction has been received from the PC
    incomingByte = Serial.read();     // If an instruction is available, store the value in IncomingByte
    if(incomingByte == 49){    // If the received value is 1 decimal/49 ASCII, then do the following       
     if(relay1_state == 0){    // Check to see the current state of relay#1.  If 0, change it to 1, and turn the relay on (low)
       relay1_state = 1;       // Set new state to 1 (on)
       digitalWrite(relay1,LOW); // turn on relay#1
     }
     else{  // If incomingByte WAS 49, BUT relay1_state was 1, then do the following:
       relay1_state = 0;          // Chance the value back to 0 (default state/OFF) and...
       digitalWrite(relay1,HIGH); // Turn the relay back off.
     }
    }     
    else if(incomingByte == 50){  // Same as above for all four relays.  No need to keep commenting.  50 ASCII = 2 Decimal
    if(relay2_state == 0){
       relay2_state = 1;
       digitalWrite(relay2,LOW);
     }
     else{
       relay2_state = 0;
       digitalWrite(relay2,HIGH);
     }
    }     
    else if(incomingByte == 51){  // 
    if(relay3_state == 0){
       relay3_state = 1;
       digitalWrite(relay3,LOW);
     }
     else{
       relay3_state = 0;
       digitalWrite(relay3,HIGH);
     }
    }     
    else if(incomingByte == 52){  // 
    if(relay4_state == 0){
       relay4_state = 1;
       digitalWrite(relay4,LOW);
     }
     else{
       relay4_state = 0;
       digitalWrite(relay4,HIGH);
     }
    }     
    else if(incomingByte == 53){  // If the incoming byte was 53 ASCII/5 decimal, turn all relays off
    digitalWrite(relay1,HIGH); // Turn relays off
    digitalWrite(relay2,HIGH);
    digitalWrite(relay3,HIGH);
    digitalWrite(relay4,HIGH);
    relay1_state = 0;          // Set all states to default state of 0/OFF
    relay2_state = 0;
    relay3_state = 0;
    relay4_state = 0;
    }    
    else{}  // If an incoming byte was received, but it wasn't 1-5/49-53 ASCII, then do nothing
    }
}   // This is the end of the program