ModularSensors > Examples > simple_logging.ino

simple_logging.ino example

Simple Logging Example

This shows the simplest use of a "logger" object. That is, creating an array of variable objects and then creating a logger object that utilizes those variables to update all of the variable results together and save the data to a SD card. The processor then goes to sleep between readings.

This is the example you should use to deploy a logger somewhere where you don't want or have access to a way of streaming live data and you won't want to upload data to the Monitor My Watershed data portal.

Unique Features of the Simple Logging Example

  • Only logs data to an SD card.

To Use this Example:

Prepare and set up PlatformIO

  • Create a new PlatformIO project
  • Replace the contents of the platformio.ini for your new project with the platformio.ini file in the examples/simple_logging folder on GitHub.
    • It is important that your PlatformIO configuration has the lib_ldf_mode and build flags set as they are in the example.
    • Without this, the program won't compile.
  • Open simple_logging.ino and save it to your computer. Put it into the src directory of your project.
    • Delete main.cpp in that folder.

Set the logger ID

  • Change the "XXXX" in this section of code to the loggerID assigned by Stroud:
// Logger ID, also becomes the prefix for the name of the data file on SD card
const char *LoggerID = "XXXX";


  • Test everything at home before deploying out in the wild!

PlatformIO Configuration

; PlatformIO Project Configuration File
;   Build options: build flags, source filter
;   Upload options: custom upload port, speed and extra flags
;   Library options: dependencies, extra library storages
;   Advanced options: extra scripting
; Please visit documentation for the other options and examples

description = ModularSensors example logging data to an SD card

monitor_speed = 115200
board = mayfly
platform = atmelavr
framework = arduino
lib_ldf_mode = deep+
lib_ignore =
    Adafruit NeoPixel
    Adafruit GFX Library
    Adafruit SSD1306
    Adafruit ADXL343
    Adafruit STMPE610
    Adafruit TouchScreen
    Adafruit ILI9341
build_flags =
lib_deps =
;  ^^ Use this when working from an official release of the library
;  ^^ Use this when if you want to pull from the develop branch
;  ^^ These are software serial port emulator libraries, you may not need them

The Complete Code

/** =========================================================================
 * @file simple_logging.ino
 * @brief A simple data logging example.
 * @author Sara Geleskie Damiano <>
 * @copyright (c) 2017-2020 Stroud Water Research Center (SWRC)
 *                          and the EnviroDIY Development Team
 *            This example is published under the BSD-3 license.
 * Build Environment: Visual Studios Code with PlatformIO
 * Hardware Platform: EnviroDIY Mayfly Arduino Datalogger
 * ======================================================================= */

// ==========================================================================
//  Include the libraries required for any data logger
// ==========================================================================
/** Start [includes] */
// The Arduino library is needed for every Arduino program.
#include <Arduino.h>

// EnableInterrupt is used by ModularSensors for external and pin change
// interrupts and must be explicitly included in the main program.
#include <EnableInterrupt.h>

// Include the main header for ModularSensors
#include <ModularSensors.h>
/** End [includes] */

// ==========================================================================
//  Data Logging Options
// ==========================================================================
/** Start [logging_options] */
// The name of this program file
const char* sketchName = "simple_logging.ino";
// Logger ID, also becomes the prefix for the name of the data file on SD card
const char* LoggerID = "XXXXX";
// How frequently (in minutes) to log data
const uint8_t loggingInterval = 5;
// Your logger's timezone.
const int8_t timeZone = -5;  // Eastern Standard Time
// NOTE:  Daylight savings time will not be applied!  Please use standard time!

// Set the input and output pins for the logger
// NOTE:  Use -1 for pins that do not apply
const int32_t serialBaud = 115200;  // Baud rate for debugging
const int8_t  greenLED   = 8;       // Pin for the green LED
const int8_t  redLED     = 9;       // Pin for the red LED
const int8_t  buttonPin  = 21;      // Pin for debugging mode (ie, button pin)
const int8_t  wakePin    = 31;  // MCU interrupt/alarm pin to wake from sleep
// Mayfly 0.x D31 = A7
// Set the wake pin to -1 if you do not want the main processor to sleep.
// In a SAMD system where you are using the built-in rtc, set wakePin to 1
const int8_t sdCardPwrPin   = -1;  // MCU SD card power pin
const int8_t sdCardSSPin    = 12;  // SD card chip select/slave select pin
const int8_t sensorPowerPin = 22;  // MCU pin controlling main sensor power
/** End [logging_options] */

// ==========================================================================
//  Using the Processor as a Sensor
// ==========================================================================
/** Start [processor_sensor] */
#include <sensors/ProcessorStats.h>

// Create the main processor chip "sensor" - for general metadata
const char*    mcuBoardVersion = "v0.5b";
ProcessorStats mcuBoard(mcuBoardVersion);
/** End [processor_sensor] */

// ==========================================================================
//  Maxim DS3231 RTC (Real Time Clock)
// ==========================================================================
/** Start [ds3231] */
#include <sensors/MaximDS3231.h>  // Includes wrapper functions for Maxim DS3231 RTC

// Create a DS3231 sensor object, using this constructor function:
MaximDS3231 ds3231(1);
/** End [ds3231] */

// ==========================================================================
//    Settings for Additional Sensors
// ==========================================================================
// Additional sensors can setup here, similar to the RTC, but only if
//   they have been supported with ModularSensors wrapper functions. See:
// Syntax for the include statement and constructor function for each sensor is
// at
//   or can be copied from the `menu_a_la_carte.ino` example

// ==========================================================================
//  Creating the Variable Array[s] and Filling with Variable Objects
// ==========================================================================
/** Start [variable_arrays] */
Variable* variableList[] = {
    new ProcessorStats_SampleNumber(&mcuBoard),
    new ProcessorStats_FreeRam(&mcuBoard),
    new ProcessorStats_Battery(&mcuBoard), new MaximDS3231_Temp(&ds3231)
    // Additional sensor variables can be added here, by copying the syntax
    //   for creating the variable pointer (FORM1) from the
    //   `menu_a_la_carte.ino` example
    // The example code snippets in the wiki are primarily FORM2.
// Count up the number of pointers in the array
int variableCount = sizeof(variableList) / sizeof(variableList[0]);

// Create the VariableArray object
VariableArray varArray;
/** End [variable_arrays] */

// ==========================================================================
//  The Logger Object[s]
// ==========================================================================
/** Start [loggers] */
// Create a logger instance
Logger dataLogger;
/** End [loggers] */

// ==========================================================================
//  Working Functions
// ==========================================================================
/** Start [working_functions] */
// Flashes the LED's on the primary board
void greenredflash(uint8_t numFlash = 4, uint8_t rate = 75) {
    for (uint8_t i = 0; i < numFlash; i++) {
        digitalWrite(greenLED, HIGH);
        digitalWrite(redLED, LOW);
        digitalWrite(greenLED, LOW);
        digitalWrite(redLED, HIGH);
    digitalWrite(redLED, LOW);
/** End [working_functions] */

// ==========================================================================
//  Arduino Setup Function
// ==========================================================================
/** Start [setup] */
void setup() {
    // Start the primary serial connection

    // Print a start-up note to the first serial port
    Serial.print(F("Now running "));
    Serial.print(F(" on Logger "));

    Serial.print(F("Using ModularSensors Library version "));

    // Set up pins for the LED's
    pinMode(greenLED, OUTPUT);
    digitalWrite(greenLED, LOW);
    pinMode(redLED, OUTPUT);
    digitalWrite(redLED, LOW);
    // Blink the LEDs to show the board is on and starting up

    // Set the timezones for the logger/data and the RTC
    // Logging in the given time zone
    // It is STRONGLY RECOMMENDED that you set the RTC to be in UTC (UTC+0)

    // Set information pins
    dataLogger.setLoggerPins(wakePin, sdCardSSPin, sdCardPwrPin, buttonPin,

    // Begin the variable array[s], logger[s], and publisher[s]
    varArray.begin(variableCount, variableList);
    dataLogger.begin(LoggerID, loggingInterval, &varArray);

    // Set up the sensors
    Serial.println(F("Setting up sensors..."));

    // Create the log file, adding the default header to it
    // Do this last so we have the best chance of getting the time correct and
    // all sensor names correct
    dataLogger.createLogFile(true);  // true = write a new header

    // Call the processor sleep
/** End [setup] */

// ==========================================================================
//  Arduino Loop Function
// ==========================================================================
/** Start [loop] */
void loop() {
/** End [loop] */