Input

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Gathering Real-Time Data

Gathering Real-Time data is rather easy using the Arduino. When connected with a computer through USB, an Arduino can print values directly to a Serial Monitor. Thankfully, there is an add-on for Matlab, which enables Matlab to read the Serial Monitor, and also return commands to the Arduino.

The Arduino needs some code to measure the input of the sound sensor, and print the values to the Serial Monitor. A preview of this code can be seen below. This code also includes peak detection. When a peak is detected, it can be printed to the Serial Monitor, but it will also turn on a light if the peak is within the given wake up time. Also, if the time exceeds the maximum of the alarm, the light will always turn on at the end. The light represents the output of this code.

Our intent was to have as much of the program running on the Arduino itself. That means that you, in theory, would be able to have the Arduino as a standalone product. In our case, that would mean you start the program from your computer, and then would be able to unplug your Arduino, since it is able to run the whole code by itself. This was however not possible because of multiple reasons. One of the reasons discussed here is saving the gathered data to read it.

For a more accurate calculation of the wake up moment, as much measurements as able should be saved. The problem is the size of the information, and saving that information on the Arduino. The used Arduino (Arduino Mega) has up to 256 KB of storage. Not all of this can be used, since a lot would already be taken up by the program itself, and 8 KB for the bootloader. If we then want to review the last 30 minutes to choose the best moment to wake up (the larger the reviewed period, the more accurate the decision), the sample time has to be reduced dramatically. Reducing the sample time results in an inaccurate measurement, leading to the program not able to choose the correct moment to wake the person. For this reason, we chose to keep the laptop in the loop for this prototype, since a laptop has more than enough storage to store samples of the whole night. In our tests, the files containing all the measurements had a size of ~130 MB.

 /*---------- Pin initialization ----------*/ 
 const int inputPin = A0;                                // Input from the sensor
 const int outputPin = 13;                               // Pin for the output light

 /*---------- Editable values ----------*/ 
 int counter = 50;                                        // Number of averages taken. Average is taken to filter out small noise 
 float timeStep = 0.1;
 int maxWakeUpTime = 60;                                 // Alarm will wake you up no later than maxWakeUpTime
 int wakeUpRange = 15;                                   // Time allowed before maxWakeUpTime
 bool printPeaks = false;                                // Testing feature; if true, it will print the peak values, otherwise, it will just print the measured values

 /*---------- Variables used by the program ----------*/ 
 int timer = 0;                                          // Clock 
 int oldValueTimer;                                      // Integer to remember old value for printing, if that turns out to be a peak
 float measurement;                                      // Sensor value
 float currentValue = 0;                                 // Current value
 float oldValue;                                         // Previous value
 bool oldPlus = false;                                   // Boolean to save if graph is increasing or decreasing 
                                                         //                             true          false
void setup() {
 Serial.begin(9600);                                     // Set up output window
 Serial.println("CLEARDATA");                            // Initialization of the Excel Table, needed for the PLX-DAQ
 Serial.println("LABEL,Time,Peak Value");                // Names of the rows, LABEL is for the PLX-DAQ
 
 pinMode(inputPin, INPUT);                               // Sensor input pin
 pinMode(outputPin, OUTPUT);                             // Light output pin
 
 digitalWrite(outputPin, LOW);                           // Light starts off being out
}

void loop() {
  for (int i = 0; i < counter; i++){                     // Loop to take average value
    delay(1000);                                         // Progress a second
    timer = timer + timeStep;
    measurement = analogRead(inputPin);
    currentValue = currentValue + measurement; 
    
    if (printPeaks == false){                            // Prints out the measurements to the Serial monitor
      Serial.print(timer);
      Serial.print(",");
      Serial.println(measurement);
    }      
  }
    currentValue = currentValue / counter;               // currentValue is now the average

    if (currentValue < oldValue && oldPlus == true){     // If the graph is just behind the peak (function is decreasing, but the last measurement was increasing) --> peak is found
      oldPlus = false;

      if (oldValueTimer >= maxWakeUpTime - wakeUpRange){ // If the peak is within waking up range
          digitalWrite(outputPin, HIGH);
      }
     
      if (printPeaks == true){                           // Print out found peaks to the Serial monitor
        Serial.print(oldValueTimer);
        Serial.print(",");
        Serial.println(oldValue);
      }
    }
    
    if (currentValue > oldValue){                        // Change oldPlus to true, indicating the function is increasing
      oldPlus = true;
    }

    if (timer >= maxWakeUpTime){
      digitalWrite(outputPin, HIGH);                     // Turn on the light hard coded if time is at the end of your alarm
    }
    
    oldValue = currentValue;                             // Update old value and reset the current value for the next loop
    oldValueTimer = timer;                                   
    currentValue = 0;
}