ESP32 Mongoose OS Interface MQTT

 

Mongoose OS Credentials configure

Two way to configure the MQTT Credentials  in Mongoose OS file. This Example tested with mongoose os , demo-js app, windows 10, 64bit, mos tool, ESP32 DevKitC from ESPressif. ESP32 Mongoose OS Interface MQTT

• First one is using mos tool  UI
  • GO to 127.0.0.1:1992/  –> Device Config  –> Change the MQTT Credential in MQTT Setting  and Save with Reboot
  • Afterwards its generate the new file name is conf9.json
• Second methods is change the mqtt Credential in conf0.json  file

 

Required

• ESP32 Any kind of boards
• Mongoose OS firmware
• Mos Tool
• MQTT Server Credentials
• WiFi Crendentials

Note : This ESP32 Mongoose OS interface – MQTT is tested with Windows 10 64bit machine, mos tool(Web Browser based IDE for Mongoose OS), ESp32 DevkitC board from ESPressif.

 

Follow

• Make sure already set your WiFi Credentials (otherwise MQTT is not work, also check the MQTT Connected status in Terminal windows)

 

Code : init.js  file

The code is designed to:

1. Monitor a physical button on a microcontroller.
2. Collect system information (RAM usage).
3. Publish this info to an MQTT topic when the button is pressed.
4. Monitor network connectivity events and print status to the console.

It uses the Mongoose OS APIs: GPIO, MQTT, System, Event, and Config.

load('api_config.js');
load('api_events.js');
load('api_gpio.js');
load('api_mqtt.js');
load('api_sys.js');

let button = Cfg.get('pins.button');
let topic = '/devices/' + Cfg.get('device.id') + '/events';

print('button GPIO:', button);

let getInfo = function() {
  return JSON.stringify({
    total_ram: Sys.total_ram(),
    free_ram: Sys.free_ram()
  });
};

// Publish to MQTT topic on a button press. Button is wired to GPIO pin 0
GPIO.set_button_handler(button, GPIO.PULL_UP, GPIO.INT_EDGE_NEG, 20, function() {
  let message = getInfo();
  let ok = MQTT.pub(topic, message, 1);
  print('Published:', ok, topic, '->', message);
}, null);

// Monitor network connectivity.
Event.addGroupHandler(Net.EVENT_GRP, function(ev, evdata, arg) {
  let evs = '???';
  if (ev === Net.STATUS_DISCONNECTED) {
    evs = 'DISCONNECTED';
  } else if (ev === Net.STATUS_CONNECTING) {
    evs = 'CONNECTING';
  } else if (ev === Net.STATUS_CONNECTED) {
    evs = 'CONNECTED';
  } else if (ev === Net.STATUS_GOT_IP) {
    evs = 'GOT_IP';
  }
  print('== Net event:', ev, evs);
}, null);

 

Output

• Results : {“free_ram”:148676,”total_ram”:229296}
• Topic : /device/esp32_0255EC/events

Code Explanation

Loading Required APIs

load('api_config.js');
load('api_events.js');
load('api_gpio.js');
load('api_mqtt.js');
load('api_sys.js');

• api_config.js → Access device configuration (pins, device ID, etc.).
• api_events.js → Handle system and network events.
• api_gpio.js → Control GPIO pins, read/write buttons and LEDs.
• api_mqtt.js → Publish/subscribe messages to MQTT broker.
• api_sys.js → Access system-level info like RAM, uptime, etc.

---

Button and MQTT Topic Setup

let button = Cfg.get('pins.button');
let topic = '/devices/' + Cfg.get('device.id') + '/events';
print('button GPIO:', button);

• Reads the GPIO pin number for the button from configuration.
• Defines the MQTT topic dynamically using the device ID.
• Prints the GPIO pin for debugging.

---

System Info Function

let getInfo = function() {
  return JSON.stringify({
    total_ram: Sys.total_ram(),
    free_ram: Sys.free_ram()
  });
};

• Creates a function that returns system RAM info as a JSON string.
• Sys.total_ram() → Total RAM on the device.
• Sys.free_ram() → Free RAM available.

---

Button Press Handler and MQTT Publish

GPIO.set_button_handler(button, GPIO.PULL_UP, GPIO.INT_EDGE_NEG, 20, function() {
  let message = getInfo();
  let ok = MQTT.pub(topic, message, 1);
  print('Published:', ok, topic, '->', message);
}, null);

• Configures the button with pull-up resistor.
• Trigger occurs on falling edge (button pressed).
• Debounce interval: 20 ms.
• On press:
  1. Reads system info using getInfo().
  2. Publishes it to the MQTT topic with QoS = 1.
  3. Prints confirmation to the console.

---

Network Event Monitoring

Event.addGroupHandler(Net.EVENT_GRP, function(ev, evdata, arg) {
  let evs = '???';
  if (ev === Net.STATUS_DISCONNECTED) {
    evs = 'DISCONNECTED';
  } else if (ev === Net.STATUS_CONNECTING) {
    evs = 'CONNECTING';
  } else if (ev === Net.STATUS_CONNECTED) {
    evs = 'CONNECTED';
  } else if (ev === Net.STATUS_GOT_IP) {
    evs = 'GOT_IP';
  }
  print('== Net event:', ev, evs);
}, null);

• Monitors network events from the NET event group.
• Prints the current network status:
  • DISCONNECTED → Not connected to WiFi.
  • CONNECTING → Attempting connection.
  • CONNECTED → WiFi connected but no IP yet.
  • GOT_IP → Successfully connected with IP.

---

Real-Time Usage

1. IoT Device Monitoring: Track device health via MQTT on-demand.
2. Remote Diagnostics: Send system RAM info when a physical button is pressed.
3. Network Status Debugging: Real-time feedback on connectivity for troubleshooting.
4. Embedded Projects: Useful in ESP32/ESP8266 or Mongoose OS projects for sensor monitoring, alerts, or control systems.

 

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