/*
   My own Linux to Arduino project with simple
   communication protocol on /dev/ttyUSB0
   V1.01 (c) 2016 Andreas Schuster
*/
String inputString = "";         // a string to hold incoming data
String cmdString = "";
String valueString = "";
boolean stringComplete = false;  // whether the string is complete
boolean cmdComplete = false;
boolean valueComplete = false;

const int ledPin = 13;
int ledstatus = 0;
int startcmd = 0;
int valuecmd = 0;
int endcmd = 0;
int serialcounter = 0;
int timer = 0;
int pin = 0;
int val = 0;
int freq = 0;

void setup() {
  // initialize serial:
  Serial.begin(38400);
  // reserve 200 bytes for the inputString:
  inputString.reserve(200);
  cmdString.reserve(40);
  valueString.reserve(40);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // change the onboard LED when a newline arrives:
  if (stringComplete) {
    //Serial.print(inputString);
    //Serial.print("\n");
    timer = 0;
    if (ledstatus == 0) {
      digitalWrite(ledPin, HIGH);
      ledstatus = 1;
    } else {
      digitalWrite(ledPin, LOW);
      ledstatus = 0;
    }
    // handle cmdString & valueString
    if (cmdComplete) {
      //      Serial.print("cmd=");
      //      Serial.print(cmdString);
      //      Serial.print(";");
    }
    if (valueComplete) {
      //      Serial.print("value=");
      //      Serial.print(valueString);
      //      Serial.print(";");
    }
    pin = 255; // false pin at start
    if (cmdString.length() >= 6) {                // typical command "out_d4" or "out_d12"
      if (cmdString.substring(0, 4) == "out_") { // found an output command
        if (cmdString.charAt(4) == 'd') {        // found to write to a digital pin
          if (isAlphaNumeric(cmdString.charAt(5))) {
            pin = cmdString.charAt(5) - char('0');
            if (cmdString.length() >= 7) {
              if (isAlphaNumeric(cmdString.charAt(6))) {
                pin = (pin * 10) + (cmdString.charAt(6) - char('0'));
              }
            }
            // write to pin
            if (pin < 100) {
              if (valueString == "HIGH") {
                pinMode(pin, OUTPUT);
                digitalWrite(pin, HIGH);
              } else if (valueString == "LOW") {
                pinMode(pin, OUTPUT);
                digitalWrite(pin, LOW);
              } else {
                Serial.print("ERROR:cannot understand value!\n");
              }
                Serial.print("OK:");
                Serial.print(cmdString);
                Serial.print(" set to ");
                Serial.print(valueString);
                Serial.print("\n");
            } else {
                Serial.print("ERROR:cannot detect pin number!\n");
            }
          }
        }
      }
    }
    if (cmdString.length() >= 5) {              // typical command "in_d4" or "in_d12"
      if (cmdString.substring(0, 3) == "in_") { // found an input command
        if (cmdString.charAt(3) == 'd') {       // found to write to a digital pin
          if (isAlphaNumeric(cmdString.charAt(4))) {
            pin = cmdString.charAt(4) - char('0');
            if (cmdString.length() >= 6) {
              if (isAlphaNumeric(cmdString.charAt(5))) {
                pin = (pin * 10) + (cmdString.charAt(5) - char('0'));
              }
            }
            // readpin here
            if (pin < 100) {
              pinMode(pin, INPUT);
              val = digitalRead(pin);
              if (val == HIGH) {
                Serial.print("HIGH\n");
              } else if (val == LOW) {
                Serial.print("LOW\n");
              } else {
                Serial.print("undefined\n");
              }
            } else {
               Serial.print("ERROR:cannot detect pin number!\n");
            }
          }
        }
      }
    }
    if (cmdString == "tone") {
      freq = valueString.toInt();
      if (freq < 40) {
        freq = 2600;
      }
      Serial.print("OK:play tone ");
      Serial.print(freq,DEC);
      Serial.print("\n");
      tone(3, freq, 2000);
    }
    if (inputString == "help\n") {
      Serial.print("output commands:\n");
      Serial.print(" ^out_d[pin]%[HIGH|LOW]$\n");
      Serial.print(" return: none\n");
      Serial.print("input commands:\n");
      Serial.print(" ^in_d[pin]$\n");
      Serial.print(" return: HIGH | LOW\n");
      Serial.print("tone command (only pin 3!):\n");
      Serial.print(" ^tone$ or ^tone%[frequency]$\n");
      Serial.print(" return: none\n");
    }
    serialcounter = 0;
    startcmd = 0;
    valuecmd = 0;
    endcmd = 0;
    // clear the string:
    inputString = "";
    cmdString = "";
    valueString = "";
    stringComplete = false;
    cmdComplete = false;
    valueComplete = false;
  }
  delay(2);
  timer++;
  if (timer > 5000) {  //periodically change the onboard LED
    timer = 0;
    if (ledstatus == 0) {
      digitalWrite(ledPin, HIGH);
      ledstatus = 1;
    } else {
      digitalWrite(ledPin, LOW);
      ledstatus = 0;
    }
  }
}

void serialEvent() {
  /* seperate a typical serial command
      e.g. "^out_d4%HIGH$"
      into
      cmdString = "out_d4"
      value = "HIGH"
  */
  while (Serial.available()) {
    // get the new byte:
    serialcounter++;
    char inChar = (char)Serial.read();
    // add it to the inputString:
    //Serial.print(inChar);
    inputString += inChar;
    // if the incoming character is a newline, set a flag
    // so the main loop can do something about it:
    if (startcmd > 0 && inChar != '%' && inChar != '$') {
      cmdString += inChar;
    }
    if (valuecmd > 0 && inChar != '$') {
      valueString += inChar;
    }
    if (inChar == '^') {
      startcmd = serialcounter;
      valuecmd = 0;
    }
    if (inChar == '%') {
      cmdComplete = true;
      valuecmd = serialcounter;
      startcmd = 0;
    }
    if (inChar == '$') {
      valuecmd = 0;
      startcmd = 0;
      cmdComplete = true;
      valueComplete = true;
      endcmd = serialcounter;
    }
    if (inChar == '\n') {
      stringComplete = true;
    }
  }
}