andriod_arduino_test

https://github.com/mik3y/usb-serial-for-android
https://github.com/kai-morich/SimpleUsbTerminal
https://github.com/mik3y/usb-serial-for-android

############## ARDUINO ##############
void setup() {
  Serial.begin(115200);
  while (!Serial) { }  // wait for a connection
  Serial.println("READY");
}

void loop() {
// connect your phone and see if you get transmission interactions
  if (Serial.available()) {
    String input = Serial.readStringUntil('\n');
    Serial.print("ECHO: ");
    Serial.println(input);
  }
}