Introduction

This sample application will allow you to control GPIO of your magicbit device using ThingsBoard web UI and display humidity/temperature data from DHT22 sensor. We will observe GPIO control using LEDs connected to the pins. The purpose of this application is to demonstrate ThingsBoard  RPC capabilities and ThingsBoard Telemetry.

The application that is running on Magicbit device is written using ThingsBoard Arduino SDK which is quite simple and easy to understand.

Current GPIO state and GPIO control widget is visualized using built-in customizable dashboard.

Once you complete this sample/tutorial, you will see your sensor data on the following dashboard.

Visit the Thingsboard Demo official page and get signed up.

After Signing in On the Left Side Bar you will see Devices. Click devices and add a new device.

On the credentials tab tick Add credentials tab and choose Access Token from the drop down box. Either you can add your own Access Token or leave blank to auto generate token.

In the Arduino IDE download the following libraries,

The following is the Arduino code you will be using.

Note You need to edit following constants and variables in the sketch:

• WIFI_AP – name of your access point
• WIFI_PASSWORD – access point password
• TOKEN – the $ACCESS_TOKEN from ThingsBoard configuration step.
• THINGSBOARD_SERVER – ThingsBoard HOST/IP address that is accessible within your wifi network. Specify demo.thingsboard.io if you are using live demo server.

#include <DHTesp.h>         // DHT for ESP32 library
#include <WiFi.h>           // WiFi control for ESP32
#include <ThingsBoard.h>    // ThingsBoard SDK

// Helper macro to calculate array size
#define COUNT_OF(x) ((sizeof(x)/sizeof(0[x])) / ((size_t)(!(sizeof(x) % sizeof(0[x])))))

// WiFi access point
#define WIFI_AP_NAME        "WIFI_AP"
// WiFi password
#define WIFI_PASSWORD       "WIFI_PASSWORD"

// See https://thingsboard.io/docs/getting-started-guides/helloworld/ 
// to understand how to obtain an access token
#define TOKEN               "TOKEN"
// ThingsBoard server instance.
#define THINGSBOARD_SERVER  "demo.thingsboard.io"

// Baud rate for debug serial
#define SERIAL_DEBUG_BAUD    115200

// Initialize ThingsBoard client
WiFiClient espClient;
// Initialize ThingsBoard instance
ThingsBoard tb(espClient);
// the Wifi radio's status
int status = WL_IDLE_STATUS;

// Array with LEDs that should be lit up one by one
uint8_t leds_cycling[] = { 25, 26, 32 };
// Array with LEDs that should be controlled from ThingsBoard, one by one
uint8_t leds_control[] = { 19, 22, 21 };

// DHT object
DHTesp dht;
// ESP32 pin used to query DHT22
#define DHT_PIN 33

// Main application loop delay
int quant = 20;

// Initial period of LED cycling.
int led_delay = 1000;
// Period of sending a temperature/humidity data.
int send_delay = 2000;

// Time passed after LED was turned ON, milliseconds.
int led_passed = 0;
// Time passed after temperature/humidity data was sent, milliseconds.
int send_passed = 0;

// Set to true if application is subscribed for the RPC messages.
bool subscribed = false;
// LED number that is currenlty ON.
int current_led = 0;

// Processes function for RPC call "setValue"
// RPC_Data is a JSON variant, that can be queried using operator[]
// See https://arduinojson.org/v5/api/jsonvariant/subscript/ for more details
RPC_Response processDelayChange(const RPC_Data &data)
{
  Serial.println("Received the set delay RPC method");

  // Process data

  led_delay = data;

  Serial.print("Set new delay: ");
  Serial.println(led_delay);

  return RPC_Response(NULL, led_delay);
}

// Processes function for RPC call "getValue"
// RPC_Data is a JSON variant, that can be queried using operator[]
// See https://arduinojson.org/v5/api/jsonvariant/subscript/ for more details
RPC_Response processGetDelay(const RPC_Data &data)
{
  Serial.println("Received the get value method");

  return RPC_Response(NULL, led_delay);
}

// Processes function for RPC call "setGpioStatus"
// RPC_Data is a JSON variant, that can be queried using operator[]
// See https://arduinojson.org/v5/api/jsonvariant/subscript/ for more details
RPC_Response processSetGpioState(const RPC_Data &data)
{
  Serial.println("Received the set GPIO RPC method");

  int pin = data["pin"];
  bool enabled = data["enabled"];

  if (pin < COUNT_OF(leds_control)) {
    Serial.print("Setting LED ");
    Serial.print(pin);
    Serial.print(" to state ");
    Serial.println(enabled);

    digitalWrite(leds_control[pin], enabled);
  }

  return RPC_Response(data["pin"], (bool)data["enabled"]);
}

// RPC handlers
RPC_Callback callbacks[] = {
  { "setValue",         processDelayChange },
  { "getValue",         processGetDelay },
  { "setGpioStatus",    processSetGpioState },
};

// Setup an application
void setup() {
  // Initialize serial for debugging
  Serial.begin(SERIAL_DEBUG_BAUD);
  WiFi.begin(WIFI_AP_NAME, WIFI_PASSWORD);
  InitWiFi();

  // Pinconfig

  for (size_t i = 0; i < COUNT_OF(leds_cycling); ++i) {
    pinMode(leds_cycling[i], OUTPUT);
  }

  for (size_t i = 0; i < COUNT_OF(leds_control); ++i) {
    pinMode(leds_control[i], OUTPUT);
  }

  // Initialize temperature sensor
  dht.setup(DHT_PIN, DHTesp::DHT22);
}

// Main application loop
void loop() {
  delay(quant);

  led_passed += quant;
  send_passed += quant;

  // Check if next LED should be lit up
  if (led_passed > led_delay) {
    // Turn off current LED
    digitalWrite(leds_cycling[current_led], LOW);
    led_passed = 0;
    current_led = current_led >= 2 ? 0 : (current_led + 1);
    // Turn on next LED in a row
    digitalWrite(leds_cycling[current_led], HIGH);
  }

  // Reconnect to WiFi, if needed
  if (WiFi.status() != WL_CONNECTED) {
    reconnect();
    return;
  }

  // Reconnect to ThingsBoard, if needed
  if (!tb.connected()) {
    subscribed = false;

    // Connect to the ThingsBoard
    Serial.print("Connecting to: ");
    Serial.print(THINGSBOARD_SERVER);
    Serial.print(" with token ");
    Serial.println(TOKEN);
    if (!tb.connect(THINGSBOARD_SERVER, TOKEN)) {
      Serial.println("Failed to connect");
      return;
    }
  }

  // Subscribe for RPC, if needed
  if (!subscribed) {
    Serial.println("Subscribing for RPC...");

    // Perform a subscription. All consequent data processing will happen in
    // callbacks as denoted by callbacks[] array.
    if (!tb.RPC_Subscribe(callbacks, COUNT_OF(callbacks))) {
      Serial.println("Failed to subscribe for RPC");
      return;
    }

    Serial.println("Subscribe done");
    subscribed = true;
  }

  // Check if it is a time to send DHT22 temperature and humidity
  if (send_passed > send_delay) {
    Serial.println("Sending data...");

    // Uploads new telemetry to ThingsBoard using MQTT. 
    // See https://thingsboard.io/docs/reference/mqtt-api/#telemetry-upload-api 
    // for more details

    TempAndHumidity lastValues = dht.getTempAndHumidity();    
    if (isnan(lastValues.humidity) || isnan(lastValues.temperature)) {
      Serial.println("Failed to read from DHT sensor!");
    } else {
      tb.sendTelemetryFloat("temperature", lastValues.temperature);
      tb.sendTelemetryFloat("humidity", lastValues.humidity);
    }

    send_passed = 0;
  }

  // Process messages
  tb.loop();
}

void InitWiFi()
{
  Serial.println("Connecting to AP ...");
  // attempt to connect to WiFi network

  WiFi.begin(WIFI_AP_NAME, WIFI_PASSWORD);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("Connected to AP");
}

void reconnect() {
  // Loop until we're reconnected
  status = WiFi.status();
  if ( status != WL_CONNECTED) {
    WiFi.begin(WIFI_AP_NAME, WIFI_PASSWORD);
    while (WiFi.status() != WL_CONNECTED) {
      delay(500);
      Serial.print(".");
    }
    Serial.println("Connected to AP");
  }
}

Data visualization and GPIO control

In live-demo server:

• login: your live-demo username (email)
• password: your live-demo password

See live-demo page for more details how to get your account.

Go to “Devices” section and locate “Magicbit”, open device details and switch to “Latest telemetry” tab. If all is configured correctly you should be able to see latest values of “temperature” and “humidity” in the table.

After, open “Dashboards” section then locate and open “Magicbit Dashboard”. As a result, you will see a time-series chart displaying temperature and humidity level (similar to dashboard image in the introduction).

You should also observe a GPIO control for your device. It consists of two widgets: one is for controlling LED blink speed (in milliseconds) and second for turning individual LEDs on and off.

You can switch status of GPIOs using control panel. As a result, you will see LEDs status change on the device. To control LED blink speed, simply turn a knob and observe a speed change.