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/*
  Serial Call and Response
  Language: Wiring/Arduino

  This program sends an ASCII A (byte of value 65) on startup and repeats that
  until it gets some data in. Then it waits for a byte in the serial port, and
  sends three sensor values whenever it gets a byte in.

  The circuit:
  - potentiometers attached to analog inputs 0 and 1
  - pushbutton attached to digital I/O 2

  created 26 Sep 2005
  by Tom Igoe
  modified 24 Apr 2012
  by Tom Igoe and Scott Fitzgerald
  Thanks to Greg Shakar and Scott Fitzgerald for the improvements

  This example code is in the public domain.

  https://www.arduino.cc/en/Tutorial/BuiltInExamples/SerialCallResponse
*/

int firstSensor = 0;    // first analog sensor
int secondSensor = 0;   // second analog sensor
int thirdSensor = 0;    // digital sensor
int inByte = 0;         // incoming serial byte
  

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void setup() {
  // start serial port at 9600 bps:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  pinMode(2, INPUT);   // digital sensor is on digital pin 2
  establishContact();  // send a byte to establish contact until receiver responds
}
 

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void loop() {
  // if we get a valid byte, read analog ins:
  if (Serial.available() > 0) {
    // get incoming byte:
    inByte = Serial.read();
    // read first analog input, divide by 4 to make the range 0-255:
    firstSensor = analogRead(A0) / 4;
    // delay 10ms to let the ADC recover:
    delay(10);
    // read second analog input, divide by 4 to make the range 0-255:
    secondSensor = analogRead(1) / 4;
    // read switch, map it to 0 or 255L
    thirdSensor = map(digitalRead(2), 0, 1, 0, 255);
    // send sensor values:
    Serial.write(firstSensor);
    Serial.write(secondSensor);
    Serial.write(thirdSensor);
  }
}
 

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void establishContact() {
  while (Serial.available() <= 0) {
    Serial.print('A');   // send a capital A
    delay(300);
  }
}