Arduino Code Generator

Generate custom Arduino firmware for your ESP32 water quality monitoring device with your specific TTN credentials.

OTAA

ESP32

LoRaWAN

Water Sensors

Required Arduino Libraries

Ensure the following libraries are installed via Arduino IDE → Tools → Manage Libraries:

MCCI LoRaWAN LMIC

OneWire

DallasTemperature

Adafruit SSD1306

Adafruit GFX Library

ESP32 board package

Install all libraries from the Arduino Library Manager or via PlatformIO. See the Installation Guide for detailed instructions.

Generate Your Custom Code

Paste your TTN credentials below. The Arduino sketch will update in real-time with your specific DevEUI, AppEUI, and AppKey. Copy the code or download the .ino file and flash it to your ESP32.

Enter TTN Device Credentials

TTN Console → Your Application → End Devices → Device Overview

AppEUI / JoinEUI — 8 bytes (LSB)

Typically all zeros. Accepts any hex format (e.g. 0x00, 0x01...).

DevEUI — 8 bytes * LSB (reverse byte order from TTN)

From TTN Console → End device → DevEUI. Use the ↕ LSB copy button.

AppKey — 16 bytes * MSB

From TTN Console → End device → AppKey. Use the MSB copy button.

Generated Arduino Sketch

Fill credentials above

#include <lmic.h>
#include "hal/hal.h"
#include <SPI.h>

#include <OneWire.h>
#include <DallasTemperature.h>

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

/* ============================================================
   STEP 1 — Paste your TTN credentials below.
   Get them from: TTN Console → Your App → End Devices → Device Overview
   ============================================================ */

/* APPEUI — LSB format, usually all-zeros */
static const u1_t PROGMEM APPEUI[8] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
void os_getArtEui(u1_t* buf) { memcpy_P(buf, APPEUI, 8); }

/* DEVEUI — LSB format (flip bytes from TTN Console) */
static const u1_t PROGMEM DEVEUI[8] = { /* DEVEUI not entered */ };
void os_getDevEui(u1_t* buf) { memcpy_P(buf, DEVEUI, 8); }

/* APPKEY — MSB format */
static const u1_t PROGMEM APPKEY[16] = {/* APPKEY not entered */
};
void os_getDevKey(u1_t* buf) { memcpy_P(buf, APPKEY, 16); }

/* ============================================================
   STEP 2 — Pin definitions (match the wiring diagram)
   ============================================================ */

#define TDS_PIN        2     // TDS sensor analog out → GPIO 2
#define PH_PIN         34    // pH sensor analog out  → GPIO 34
#define ONE_WIRE_BUS   14    // DS18B20 data          → GPIO 14

/* ============================================================
   OLED (128×64 SSD1306) — I²C on SDA=21, SCL=22
   ============================================================ */

#define SCREEN_WIDTH  128
#define SCREEN_HEIGHT  64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

/* ============================================================
   LoRa SX1276 SPI pin map (MCCI LMIC)
     NSS  → GPIO 5
     RST  → GPIO 26
     DIO0 → GPIO 25
     DIO1 → GPIO 33
     DIO2 → GPIO 32
     MOSI → GPIO 23 (default SPI)
     MISO → GPIO 19 (default SPI)
     SCK  → GPIO 18 (default SPI)
   ============================================================ */

const lmic_pinmap lmic_pins = {
  .nss  = 5,
  .rxtx = LMIC_UNUSED_PIN,
  .rst  = 26,
  .dio  = { 25, 33, 32 },
};

/* ── Temperature (DS18B20) ──────────────────────────────────── */

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
float temperature = 25;

/* ── TDS ────────────────────────────────────────────────────── */

#define VREF   3.3
#define SCOUNT 30

float   baseline = 1.83; // calibration offset (adjust if needed)
int     analogBuffer[SCOUNT];
int     analogBufferTemp[SCOUNT];
float   tdsValue = 0;

/* ── pH ─────────────────────────────────────────────────────── */

float calibrationOffset = 13.50; // adjust for your pH probe
int   phBuffer[10];
float phValue = 7;

/* ── Timers ─────────────────────────────────────────────────── */

unsigned long lastSensorTime  = 0;
unsigned long lastDisplayTime = 0;
const unsigned long SENSOR_INTERVAL  = 2000; // ms
const unsigned long DISPLAY_INTERVAL = 2000; // ms

/* ── LoRa payload ───────────────────────────────────────────── */

static uint8_t mydata[6];
static osjob_t sendjob;
const unsigned TX_INTERVAL = 60; // seconds between uplinks

/* ── Median filter ──────────────────────────────────────────── */

int getMedianNum(int bArray[], int iFilterLen) {
  int bTab[iFilterLen];
  for (byte i = 0; i < iFilterLen; i++) bTab[i] = bArray[i];
  int i, j, temp;
  for (j = 0; j < iFilterLen - 1; j++)
    for (i = 0; i < iFilterLen - j - 1; i++)
      if (bTab[i] > bTab[i + 1]) {
        temp = bTab[i]; bTab[i] = bTab[i + 1]; bTab[i + 1] = temp;
      }
  if ((iFilterLen & 1) > 0) temp = bTab[(iFilterLen - 1) / 2];
  else temp = (bTab[iFilterLen / 2] + bTab[iFilterLen / 2 - 1]) / 2;
  return temp;
}

/* ── Read pH ────────────────────────────────────────────────── */

void readPH() {
  for (int i = 0; i < 10; i++) phBuffer[i] = analogRead(PH_PIN);
  long sum = 0;
  for (int i = 2; i < 8; i++) sum += phBuffer[i];
  float voltage = (float)sum * 3.3 / 4095.0 / 6.0;
  phValue = -4.90 * voltage + calibrationOffset;
}

/* ── Read all sensors ───────────────────────────────────────── */

void readSensors() {
  sensors.requestTemperatures();
  temperature = sensors.getTempCByIndex(0);

  for (int i = 0; i < SCOUNT; i++) analogBuffer[i] = analogRead(TDS_PIN);
  for (int i = 0; i < SCOUNT; i++) analogBufferTemp[i] = analogBuffer[i];

  float avgVoltage = getMedianNum(analogBufferTemp, SCOUNT) * VREF / 4095.0;
  float correctedVoltage = avgVoltage - baseline;
  if (correctedVoltage < 0) correctedVoltage = 0;

  float compCoeff   = 1.0 + 0.02 * (temperature - 25.0);
  float compVoltage = correctedVoltage / compCoeff;

  tdsValue = (133.42 * compVoltage * compVoltage * compVoltage
            - 255.86 * compVoltage * compVoltage
            + 857.39 * compVoltage) * 0.5;

  readPH();
}

/* ── Update OLED ────────────────────────────────────────────── */

void updateDisplay() {
  display.clearDisplay();
  display.setCursor(0,  0); display.print("Water Monitor");
  display.setCursor(0, 18); display.print("Temp: "); display.print(temperature, 1); display.print(" C");
  display.setCursor(0, 34); display.print("TDS:  "); display.print(tdsValue, 0);    display.print(" ppm");
  display.setCursor(0, 50); display.print("pH:   "); display.print(phValue, 2);
  display.display();
}

/* ── LMIC event handler ─────────────────────────────────────── */

void onEvent(ev_t ev) {
  switch (ev) {
    case EV_JOINING:
      Serial.println("Joining TTN...");
      break;
    case EV_JOINED:
      Serial.println("Joined TTN!");
      LMIC_setLinkCheckMode(0);
      break;
    case EV_TXCOMPLETE:
      Serial.println("Uplink sent.");
      os_setTimedCallback(&sendjob, os_getTime() + sec2osticks(TX_INTERVAL), do_send);
      break;
    default:
      break;
  }
}

/* ── Build & queue uplink packet ────────────────────────────── */

void do_send(osjob_t* j) {
  if (LMIC.opmode & OP_TXRXPEND) { Serial.println("TX pending"); return; }

  int tempInt = temperature * 10;
  int tdsInt  = tdsValue;
  int phInt   = phValue * 100;

  mydata[0] = highByte(tempInt); mydata[1] = lowByte(tempInt);
  mydata[2] = highByte(tdsInt);  mydata[3] = lowByte(tdsInt);
  mydata[4] = highByte(phInt);   mydata[5] = lowByte(phInt);

  LMIC_setTxData2(1, mydata, sizeof(mydata), 0);
  Serial.println("Packet queued.");
}

/* ── Setup ──────────────────────────────────────────────────── */

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
  analogSetAttenuation(ADC_11db);

  sensors.begin();

  Wire.begin(21, 22); // SDA=21, SCL=22
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.clearDisplay();
  display.setCursor(0, 0);
  display.println("JalRakshak.AI");
  display.println("Starting...");
  display.display();

  os_init();
  LMIC_reset();
  do_send(&sendjob);
}

/* ── Loop ───────────────────────────────────────────────────── */

void loop() {
  os_runloop_once();

  unsigned long now = millis();

  if (now - lastSensorTime >= SENSOR_INTERVAL) {
    lastSensorTime = now;
    readSensors();
    Serial.printf("Temp: %.1f | TDS: %.0f ppm | pH: %.2f\n", temperature, tdsValue, phValue);
  }

  if (now - lastDisplayTime >= DISPLAY_INTERVAL) {
    lastDisplayTime = now;
    updateDisplay();
  }
}

Code Features & Capabilities

LoRaWAN & Communication

OTAA (Over-The-Air Activation) for secure join
60-second transmission interval (battery-friendly)
Automatic rejoin on network failure
Adaptive Data Rate (ADR) support

Sensor Management

pH sensor with calibration support
TDS sensor with baseline calibration
DS18B20 temperature compensation
OLED display for live sensor readings

Data Payload

6-byte efficient payload format
Temperature (÷10) • TDS • pH (÷100)
Compatible with TTN uplink decoder
Automatic data type conversion

Debugging & Monitoring

Serial monitor output (115200 baud)
Join status and uplink confirmations
Real-time sensor value display on OLED
Error handling and recovery mechanisms

How to Use

1
Get TTN Credentials
From your TTN Console device page, copy DevEUI (LSB format) and AppKey (MSB format). See TTN Setup guide for details.
2
Paste Credentials
Enter your DevEUI and AppKey in the form above. The code will automatically update with your credentials.
3
Verify Configuration
Check that the LMIC library region is configured correctly (CFG_in866 for India). See Installation guide.
4
Upload to ESP32
Copy the generated code or download the .ino file. Open in Arduino IDE, select ESP32 board, and upload.
5
Monitor Serial Output
Open Serial Monitor (115200 baud) to see join attempts, sensor readings, and uplink confirmations.

Sensor Calibration

Calibration Required

For accurate readings, calibrate your sensors before deployment. The generated code includes calibration constants that you can adjust.

TDS Sensor Calibration

Adjust the baseline value:

float baseline = 1.83; // TDS voltage offset

Measure distilled water (should read 0 ppm) and adjust baseline accordingly.

pH Sensor Calibration

Adjust the calibrationOffset value:

float calibrationOffset = 13.50; // pH probe intercept

Use a pH 7.0 buffer solution to calibrate. Adjust offset until reading matches 7.0.

Troubleshooting Tips

❌ Device not joining TTN network

Verify DevEUI and AppKey match TTN Console exactly (check byte order: LSB vs MSB)
Ensure LMIC library region configuration matches your frequency plan (CFG_in866 for India)
Check gateway coverage using TTN Coverage Map
Verify antenna is properly connected to LoRa module

❌ Sensor readings inaccurate

Calibrate sensors using known reference solutions (pH 7.0 buffer, distilled water)
Check sensor connections and ensure proper voltage levels (3.3V)
Verify DS18B20 has 4.7kΩ pull-up resistor on data line
Allow sensors to stabilize for 2-3 minutes after immersion

❌ Uplinks successful but dashboard not updating

Check webhook configuration in TTN Console (see Webhooks guide)
Verify payload decoder is correctly set up in TTN
Ensure device ID in TTN matches device ID in dashboard
Check Serial Monitor for payload structure confirmation

Code Generated Successfully!

Upload the code to your ESP32 and configure TTN webhook integration.

Configure TTN Setup Setup Webhooks

Circuit Diagram

TTN Setup