Log voltage/time with Arduino

TinyLogger_test.ino

// Created by: WestleyR
// Email: westleyr@nym.hush.com
// Url: https://github.com/WestleyR/...
// Date created: 2021-01-20
// Last modified date: 2021-01-20
//
// This is free and unencumbered software released into the public domain.
// For more information, please refer to <https://unlicense.org>
//

/*

# How to use

Conect A0 (or another analog input of your choice) to the voltage divider,
which values you haft to decide yourself. In my case, I used 1K/320, for a
max of ~20.5v

Then, you will need to connect your laptop (or other device that can listen on
the serial port), and redirect/tee the output to a file, which will look like:

```
2.12  0.01
2.12  0.02
2.11  0.03
2.13  0.04
2.12  0.05
[...]
```

From that file, you can use a program (like gnuplot) to create a graph. See:
https://gist.github.com/WestleyR/124ff82093df6d59d308f272a0fbf4ed for a gnuplot
example.


**This code needs lots of improvments!**

This is the first, testing version of the TinyLogger product, which will be
avalibe around a couple months.

*/

// The analog sensor input pin
#define sensorPin A0

// The number of analog readings to make, and avrage it
#define numberOfReadings 25

// The voltage calibration value, this depends on your voltage
// divider. For a 1K/320, its about 4.18, with a max of ~20.5v.
const static float voltageCalibrate = 4.18;

//******
// Setup
//******
void setup() {
  Serial.begin(9600);
}

unsigned long timerValue;

void loop() {
  // Loop every 0.01s
  while ((millis() - timerValue) > 600) {

    // Read the voltage on the analog input pin a bunch of
    // times, then avrage the value.
    float avrageVolts = 0;
    for (int i = 0; i < numberOfReadings; i++) {
      int sensorValue = analogRead(sensorPin);
      float voltage = sensorValue * (5.0 / 1023.0);

      voltage *= voltageCalibrate;

      avrageVolts += voltage;
    }
    avrageVolts /= numberOfReadings;

    // Print the voltage
    Serial.print(avrageVolts);
    Serial.print("  ");

    // Print the time, in 0.01 minute resolution
    Serial.println((float)millis() / 60000);

    // Reset the timer value
    timerValue = millis();
  }
}