DRWI Digi LTE Sites

This example uses the sensors and equipment common to older stations (2016-2020) deployed by groups participating in the DRWI Citizen Science project with the Stroud Water Research Center. It includes a Meter Hydros21 CTD (formerly know as a Decagon), a Campbell OBS3+ (Turbidity), and a Digi XBee3 LTE-M cellular board for communication. The Digi LTE module also required the use of a EnviroDIY LTEbee Adapter board (discontinued in 2021). The Digi LTE modules are no longer recommended for use and have been replace by the EnviroDIY LTEbee in all DRWI-SWRC-managed stations.

The exact hardware configuration used in this example:

Mayfly v0.5b board
Digi XBee LTE module (with Hologram SIM card and EnviroDIY bee adapter)
Hydros21 CTD sensor
Campbell OBS3+ turbidity sensor

Unique Features of the DRWI Digi LTE Example

Specifically for sites within the Delaware River Watershed Initiative.
Uses a Digi XBee3 LTE-M for live data.

To Use this Example

Prepare and set up PlatformIO

Register a site and sensors at the Monitor My Watershed/EnviroDIY data portal (http://monitormywatershed.org/)
Create a new PlatformIO project
Replace the contents of the platformio.ini for your new project with the platformio.ini file in the examples/DRWI_DigiLTE 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 DRWI_DigiLTE.ino and save it to your computer.
- After opening the link, you should be able to right click anywhere on the page and select "Save Page As".
- Move 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";

Set the calibration coefficients for the Campbell OBS3+

The OBS3+ ships with a calibration certificate; you need this sheet!
Change all of the the 0.000E+00 and 1.000E+00 values in this section of code to the values on that calibration sheet. Use numbers from the side of the calibration sheet that shows the calibration in volts.
- The sketch will not compile if these values are not entered properly.
- Do not change any values except those that are 0.000E+00 and 1.000E+00!

// ==========================================================================
//  Campbell OBS 3 / OBS 3+ Analog Turbidity Sensor
// ==========================================================================
#include <sensors/CampbellOBS3.h>
const int8_t OBS3Power = sensorPowerPin;  // Power pin (-1 if unconnected)
const uint8_t OBS3numberReadings = 10;
const uint8_t ADSi2c_addr = 0x48;  // The I2C address of the ADS1115 ADC
// Campbell OBS 3+ *Low* Range Calibration in Volts
const int8_t OBSLowADSChannel = 0;  // ADS channel for *low* range output
const float OBSLow_A = 0.000E+00;  // "A" value (X^2) [*low* range]
const float OBSLow_B = 1.000E+00;  // "B" value (X) [*low* range]
const float OBSLow_C = 0.000E+00;  // "C" value [*low* range]
CampbellOBS3 osb3low(OBS3Power, OBSLowADSChannel, OBSLow_A, OBSLow_B, OBSLow_C, ADSi2c_addr, OBS3numberReadings);
// Campbell OBS 3+ *High* Range Calibration in Volts
const int8_t OBSHighADSChannel = 1;  // ADS channel for *high* range output
const float OBSHigh_A = 0.000E+00;  // "A" value (X^2) [*high* range]
const float OBSHigh_B = 1.000E+00;  // "B" value (X) [*high* range]
const float OBSHigh_C = 0.000E+00;  // "C" value [*high* range]
CampbellOBS3 osb3high(OBS3Power, OBSHighADSChannel, OBSHigh_A, OBSHigh_B, OBSHigh_C, ADSi2c_addr, OBS3numberReadings);

Set the universally universal identifiers (UUID) for each variable

Go back to the web page for your site at the Monitor My Watershed/EnviroDIY data portal (http://monitormywatershed.org/)
Find and click the white "View Token UUID List" button above the small map on your site page
VERY CAREFULLY check that the variables are in exactly the same order as in the variable array:

Variable* variableList[] = {
    ...
}

If any of the variables are in a different order on the web page than in your code reorder the variables in your code to match the website.
After you are completely certain that you have the order right in the variable section of your code use the teal "Copy" button on the website to copy the section of code containing all of the UUID's.
Paste the code from the website into your program in this section below the variable array

// *** CAUTION --- CAUTION --- CAUTION --- CAUTION --- CAUTION ***
// Check the order of your variables in the variable list!!!
// Be VERY certain that they match the order of your UUID's!
// Rearrange the variables in the variable list if necessary to match!
// *** CAUTION --- CAUTION --- CAUTION --- CAUTION --- CAUTION ***
/* clang-format off */
const char* UUIDs[] = {
    "12345678-abcd-1234-ef00-1234567890ab",  // Electrical conductivity (Decagon_CTD-10_Cond)
    "12345678-abcd-1234-ef00-1234567890ab",  // Temperature (Decagon_CTD-10_Temp)
    "12345678-abcd-1234-ef00-1234567890ab",  // Water depth (Decagon_CTD-10_Depth)
    "12345678-abcd-1234-ef00-1234567890ab",  // Turbidity (Campbell_OBS3_Turb)
    "12345678-abcd-1234-ef00-1234567890ab",  // Turbidity (Campbell_OBS3_Turb)
    "12345678-abcd-1234-ef00-1234567890ab",  // Battery voltage (EnviroDIY_Mayfly_Batt)
    "12345678-abcd-1234-ef00-1234567890ab",  // Temperature (EnviroDIY_Mayfly_Temp)
    "12345678-abcd-1234-ef00-1234567890ab",  // Received signal strength indication (Digi_Cellular_RSSI)
    "12345678-abcd-1234-ef00-1234567890ab"   // Percent full scale (Digi_Cellular_SignalPercent)
};
const char* registrationToken = "12345678-abcd-1234-ef00-1234567890ab";  // Device registration token
const char* samplingFeature = "12345678-abcd-1234-ef00-1234567890ab";  // Sampling feature UUID
/* clang-format on */

Upload!

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
; http://docs.platformio.org/page/projectconf.html

[platformio]
description = ModularSensors example intended for DRWI users with CTD, turbidity, and a Digi brand LTE modem

[env:mayfly]
monitor_speed = 57600
board = mayfly
platform = atmelavr
framework = arduino
lib_ldf_mode = deep+
lib_ignore =
    RTCZero
    Adafruit NeoPixel
    Adafruit GFX Library
    Adafruit SSD1306
    Adafruit ADXL343
    Adafruit STMPE610
    Adafruit TouchScreen
    Adafruit ILI9341
build_flags =
    -DSDI12_EXTERNAL_PCINT
lib_deps =
    envirodiy/EnviroDIY_ModularSensors
;  ^^ Use this when working from an official release of the library
;    https://github.com/EnviroDIY/ModularSensors.git#develop
;  ^^ Use this when if you want to pull from the develop branch

The Complete Code

/** =========================================================================
 * @example{lineno} DRWI_DigiLTE.ino
 * @copyright Stroud Water Research Center
 * @license This example is published under the BSD-3 license.
 * @author Sara Geleskie Damiano <sdamiano@stroudcenter.org>
 *
 * @brief Example for DRWI CitSci LTE sites.
 *
 * See [the walkthrough page](@ref example_drwi_digilte) for detailed
 * instructions.
 *
 * @m_examplenavigation{example_drwi_digilte,}
 * ======================================================================= */

// ==========================================================================
//  Defines for TinyGSM
// ==========================================================================
/** Start [defines] */
#ifndef TINY_GSM_RX_BUFFER
#define TINY_GSM_RX_BUFFER 64
#endif
#ifndef TINY_GSM_YIELD_MS
#define TINY_GSM_YIELD_MS 2
#endif
/** End [defines] */

// ==========================================================================
//  Include the libraries required for any data logger
// ==========================================================================
/** Start [includes] */
// The Arduino library is needed for every Arduino program.
#include <Arduino.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 = "DRWI_DigiLTE.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 = 15;
// 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 = 57600;  // 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] */


// ==========================================================================
//  Wifi/Cellular Modem Options
// ==========================================================================
/** Start [digi_xbee_cellular_transparent] */
// For any Digi Cellular XBee's
// NOTE:  The u-blox based Digi XBee's (3G global and LTE-M global)
// are more stable used in bypass mode (below)
// The Telit based Digi XBees (LTE Cat1) can only use this mode.
#include <modems/DigiXBeeCellularTransparent.h>

// Create a reference to the serial port for the modem
HardwareSerial& modemSerial = Serial1;  // Use hardware serial if possible
const int32_t   modemBaud   = 9600;     // All XBee's use 9600 by default

// Modem Pins - Describe the physical pin connection of your modem to your board
// NOTE:  Use -1 for pins that do not apply
const int8_t modemVccPin    = -2;    // MCU pin controlling modem power
const int8_t modemStatusPin = 19;    // MCU pin used to read modem status
const bool useCTSforStatus = false;  // Flag to use the modem CTS pin for status
const int8_t modemResetPin = 20;     // MCU pin connected to modem reset pin
const int8_t modemSleepRqPin = 23;   // MCU pin for modem sleep/wake request
const int8_t modemLEDPin = redLED;   // MCU pin connected an LED to show modem
                                     // status (-1 if unconnected)

// Network connection information
const char* apn = "hologram";  // The APN for the gprs connection

DigiXBeeCellularTransparent modemXBCT(&modemSerial, modemVccPin, modemStatusPin,
                                      useCTSforStatus, modemResetPin,
                                      modemSleepRqPin, apn);
// Create an extra reference to the modem by a generic name
DigiXBeeCellularTransparent modem = modemXBCT;
/** End [digi_xbee_cellular_transparent] */


// ==========================================================================
//  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>

// Create a DS3231 sensor object
MaximDS3231 ds3231(1);
/** End [ds3231] */


// ==========================================================================
//  Campbell OBS 3 / OBS 3+ Analog Turbidity Sensor
// ==========================================================================
/** Start [obs3] */
#include <sensors/CampbellOBS3.h>

const int8_t  OBS3Power = sensorPowerPin;  // Power pin (-1 if unconnected)
const uint8_t OBS3NumberReadings = 10;
const uint8_t ADSi2c_addr        = 0x48;  // The I2C address of the ADS1115 ADC
// Campbell OBS 3+ *Low* Range Calibration in Volts
const int8_t OBSLowADSChannel = 0;  // ADS channel for *low* range output
const float  OBSLow_A         = 0.000E+00;  // "A" value (X^2) [*low* range]
const float  OBSLow_B         = 1.000E+00;  // "B" value (X) [*low* range]
const float  OBSLow_C         = 0.000E+00;  // "C" value [*low* range]

// Create a Campbell OBS3+ *low* range sensor object
CampbellOBS3 osb3low(OBS3Power, OBSLowADSChannel, OBSLow_A, OBSLow_B, OBSLow_C,
                     ADSi2c_addr, OBS3NumberReadings);


// Campbell OBS 3+ *High* Range Calibration in Volts
const int8_t OBSHighADSChannel = 1;  // ADS channel for *high* range output
const float  OBSHigh_A         = 0.000E+00;  // "A" value (X^2) [*high* range]
const float  OBSHigh_B         = 1.000E+00;  // "B" value (X) [*high* range]
const float  OBSHigh_C         = 0.000E+00;  // "C" value [*high* range]

// Create a Campbell OBS3+ *high* range sensor object
CampbellOBS3 osb3high(OBS3Power, OBSHighADSChannel, OBSHigh_A, OBSHigh_B,
                      OBSHigh_C, ADSi2c_addr, OBS3NumberReadings);
/** End [obs3] */


// ==========================================================================
//  Meter Hydros 21 Conductivity, Temperature, and Depth Sensor
// ==========================================================================
/** Start [hydros21] */
#include <sensors/MeterHydros21.h>

const char*   hydrosSDI12address = "1";  // The SDI-12 Address of the Hydros 21
const uint8_t hydrosNumberReadings = 6;  // The number of readings to average
const int8_t  SDI12Power = sensorPowerPin;  // Power pin (-1 if unconnected)
const int8_t  SDI12Data  = 7;               // The SDI12 data pin

// Create a Meter Hydros 21 sensor object
MeterHydros21 hydros(*hydrosSDI12address, SDI12Power, SDI12Data,
                     hydrosNumberReadings);
/** End [hydros21] */


// ==========================================================================
//  Creating the Variable Array[s] and Filling with Variable Objects
// ==========================================================================
/** Start [variable_arrays] */
Variable* variableList[] = {
    new MeterHydros21_Cond(&hydros),
    new MeterHydros21_Depth(&hydros),
    new MeterHydros21_Temp(&hydros),
    new CampbellOBS3_Turbidity(&osb3low, "", "TurbLow"),
    new CampbellOBS3_Turbidity(&osb3high, "", "TurbHigh"),
    new ProcessorStats_Battery(&mcuBoard),
    new MaximDS3231_Temp(&ds3231),
    new Modem_SignalPercent(&modem),
};

// All UUID's, device registration, and sampling feature information can be
// pasted directly from Monitor My Watershed.
// To get the list, click the "View  token UUID list" button on the upper right
// of the site page.

// *** CAUTION --- CAUTION --- CAUTION --- CAUTION --- CAUTION ***
// Check the order of your variables in the variable list!!!
// Be VERY certain that they match the order of your UUID's!
// Rearrange the variables in the variable list ABOVE if necessary to match!
// Do not change the order of the variables in the section below.
// *** CAUTION --- CAUTION --- CAUTION --- CAUTION --- CAUTION ***

// Replace all of the text in the following section with the UUID array from
// MonitorMyWatershed

/* clang-format off */
// ---------------------   Beginning of Token UUID List   ---------------------


const char* UUIDs[] =  // UUID array for device sensors
    {
        "12345678-abcd-1234-ef00-1234567890ab",  // Specific conductance (Meter_Hydros21_Cond)
        "12345678-abcd-1234-ef00-1234567890ab",  // Water depth (Meter_Hydros21_Depth)
        "12345678-abcd-1234-ef00-1234567890ab",  // Temperature (Meter_Hydros21_Temp)
        "12345678-abcd-1234-ef00-1234567890ab",  // Turbidity (Campbell_OBS3_Turb) (Low)
        "12345678-abcd-1234-ef00-1234567890ab",  // Turbidity (Campbell_OBS3_Turb) (High)
        "12345678-abcd-1234-ef00-1234567890ab",  // Battery voltage (EnviroDIY_Mayfly_Batt)
        "12345678-abcd-1234-ef00-1234567890ab",  // Battery voltage (EnviroDIY_Mayfly_Batt)
        "12345678-abcd-1234-ef00-1234567890ab",  // Percent full scale (Digi_Cellular_SignalPercent)
};
const char* registrationToken = "12345678-abcd-1234-ef00-1234567890ab";  // Device registration token
const char* samplingFeature = "12345678-abcd-1234-ef00-1234567890ab";  // Sampling feature UUID


// -----------------------   End of Token UUID List  -----------------------
/* clang-format on */

// Count up the number of pointers in the array
int variableCount = sizeof(variableList) / sizeof(variableList[0]);

// Create the VariableArray object
VariableArray varArray(variableCount, variableList, UUIDs);
/** End [variable_arrays] */


// ==========================================================================
//  The Logger Object[s]
// ==========================================================================
/** Start [loggers] */
// Create a new logger instance
Logger dataLogger(LoggerID, loggingInterval, &varArray);
/** End [loggers] */


// ==========================================================================
//  Creating Data Publisher[s]
// ==========================================================================
/** Start [publishers] */
// Create a data publisher for the Monitor My Watershed/EnviroDIY POST endpoint
#include <publishers/EnviroDIYPublisher.h>
EnviroDIYPublisher EnviroDIYPOST(dataLogger, &modem.gsmClient,
                                 registrationToken, samplingFeature);
/** End [publishers] */


// ==========================================================================
//  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);
        delay(rate);
        digitalWrite(greenLED, LOW);
        digitalWrite(redLED, HIGH);
        delay(rate);
    }
    digitalWrite(redLED, LOW);
}

// Reads the battery voltage
// NOTE: This will actually return the battery level from the previous update!
float getBatteryVoltage() {
    if (mcuBoard.sensorValues[0] == -9999) mcuBoard.update();
    return mcuBoard.sensorValues[0];
}


// ==========================================================================
// Arduino Setup Function
// ==========================================================================
/** Start [setup] */
void setup() {
    // Start the primary serial connection
    Serial.begin(serialBaud);

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

    Serial.print(F("Using ModularSensors Library version "));
    Serial.println(MODULAR_SENSORS_VERSION);
    Serial.print(F("TinyGSM Library version "));
    Serial.println(TINYGSM_VERSION);
    Serial.println();

    // Start the serial connection with the modem
    modemSerial.begin(modemBaud);

    // 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
    greenredflash();

    pinMode(20, OUTPUT);  // for proper operation of the onboard flash memory
                          // chip's ChipSelect (Mayfly v1.0 and later)

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

    // Attach the modem and information pins to the logger
    dataLogger.attachModem(modem);
    modem.setModemLED(modemLEDPin);
    dataLogger.setLoggerPins(wakePin, sdCardSSPin, sdCardPwrPin, buttonPin,
                             greenLED);

    // Begin the logger
    dataLogger.begin();

    // Note:  Please change these battery voltages to match your battery
    // Set up the sensors, except at lowest battery level
    if (getBatteryVoltage() > 3.4) {
        Serial.println(F("Setting up sensors..."));
        varArray.setupSensors();
    }

    // Extra modem set-up - selecting AT&T as the carrier and LTE-M only
    // NOTE:  The code for this could be shortened using the "commandMode" and
    // other XBee specific commands in TinyGSM.  I've written it this way in
    // this example to show how the settings could be changed in either bypass
    // OR transparent mode.
    Serial.println(F("Waking modem and setting Cellular Carrier Options..."));
    modem.modemWake();  // NOTE:  This will also set up the modem
    // Go back to command mode to set carrier options
    for (uint8_t i = 0; i < 5; i++) {
        // Wait the required guard time before entering command mode
        delay(1010);
        modem.gsmModem.streamWrite(GF("+++"));  // enter command mode
        if (modem.gsmModem.waitResponse(2000, GF("OK\r")) == 1) break;
    }
    // Carrier Profile - 0 = Automatic selection
    //                 - 1 = No profile/SIM ICCID selected
    //                 - 2 = AT&T
    //                 - 3 = Verizon
    // NOTE:  To select T-Mobile, you must enter bypass mode!
    modem.gsmModem.sendAT(GF("CP"), 2);
    modem.gsmModem.waitResponse(GF("OK\r"));
    // Cellular network technology - 0 = LTE-M with NB-IoT fallback
    //                             - 1 = NB-IoT with LTE-M fallback
    //                             - 2 = LTE-M only
    //                             - 3 = NB-IoT only
    modem.gsmModem.sendAT(GF("N#"), 2);
    modem.gsmModem.waitResponse();
    // Write changes to flash and apply them
    Serial.println(F("Wait while applying changes..."));
    // Write changes to flash
    modem.gsmModem.sendAT(GF("WR"));
    modem.gsmModem.waitResponse(GF("OK\r"));
    // Apply changes
    modem.gsmModem.sendAT(GF("AC"));
    modem.gsmModem.waitResponse(GF("OK\r"));
    // Reset the cellular component to ensure network settings are changed
    modem.gsmModem.sendAT(GF("!R"));
    modem.gsmModem.waitResponse(30000L, GF("OK\r"));
    // Force reset of the Digi component as well
    // This effectively exits command mode
    modem.gsmModem.sendAT(GF("FR"));
    modem.gsmModem.waitResponse(5000L, GF("OK\r"));

    // Sync the clock if it isn't valid or we have battery to spare
    if (getBatteryVoltage() > 3.55 || !dataLogger.isRTCSane()) {
        // Synchronize the RTC with NIST
        // This will also set up the modem
        dataLogger.syncRTC();
    }

    // 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
    // Writing to the SD card can be power intensive, so if we're skipping
    // the sensor setup we'll skip this too.
    if (getBatteryVoltage() > 3.4) {
        Serial.println(F("Setting up file on SD card"));
        dataLogger.turnOnSDcard(
            true);  // true = wait for card to settle after power up
        dataLogger.createLogFile(true);  // true = write a new header
        dataLogger.turnOffSDcard(
            true);  // true = wait for internal housekeeping after write
    }

    // Call the processor sleep
    Serial.println(F("Putting processor to sleep\n"));
    dataLogger.systemSleep();
}
/** End [setup] */


// ==========================================================================
//  Arduino Loop Function
// ==========================================================================
/** Start [loop] */
// Use this short loop for simple data logging and sending
void loop() {
    // Note:  Please change these battery voltages to match your battery
    // At very low battery, just go back to sleep
    if (getBatteryVoltage() < 3.4) {
        dataLogger.systemSleep();
    }
    // At moderate voltage, log data but don't send it over the modem
    else if (getBatteryVoltage() < 3.55) {
        dataLogger.logData();
    }
    // If the battery is good, send the data to the world
    else {
        dataLogger.logDataAndPublish();
    }
}
/** End [loop] */

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