MQTTGateway

This sketch will turn an ESP-01 into a UART to MQTT gateway. It uses a very simple serial protocol to configure the WiFi and MQTT serrtings, and to subscribe to and publish messages to topics.

Requires my CLI library: https://github.com/MajenkoLibraries/CLI

The default baud rate is 9600.

Commands

set <key> <value>

Sets a configuration value. Current values are:

• ssid - the WiFi SSID to connect to
• psk - the pre-shared key (password) for your WiFi connection
• server - the MQTT server to connect to
• port - the port of the MQTT server (1883)
• devid - the client "device ID" of this unit
• user - login username for the MQTT server
• pass - login password for the MQTT server

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get [key]

Gets all the (or one specified) configuration values.

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unset <key>

Clears the value associated with one of the configuration settings

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status

Displays the current status of the system: connection status of both WiFi and MQTT, IP addresses, and any topics subscribed to.

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sub <topic>

Subscribe to a topic.

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unsub <topic>

Unsubscribe from a topic.

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pub [retain] <topic> <message>

Publish (and optionally retain) a message to a topic. If the topic contains spaces it should be wrapped in quotes.

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All commands return either "OK" or "ERR" followed by an error message. Any extra information is returned before the OK or ERR and is prefixed by |

Unsolicited messages (event and publish notifications) are prefixed with %. There are two basic types:

• Event notifications

These all start with %EVT and notify you of system events, including WiFi connection and disconnection and MQTT connection and disconnection. For example:

%EVT WiFi connected
%EVT WiFi disconnected
%EVT MQTT connected
%EVT MQTT disconnected

• Publication events

When a message is published to one of the topics you are subscribed to the topic and message are given to you as a PUB event. For instance:

%PUB topic/you/sub/to This is your message

Or:

%PUB weather/temperature 34.2

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Example Arduino Sketch

#include <SoftwareSerial.h>

SoftwareSerial ESP(10, 11);

void setup() {
    ESP.begin(9600);

    ESP.println("set ssid MyWifi");
    ESP.find('\n');
    ESP.println("set psk MyWifiPassword");
    ESP.find('\n');

    ESP.println("set server io.adafruit.com");
    ESP.find('\n');
    ESP.println("set port 1883");
    ESP.find('\n');
    ESP.println("set devid MyDevice");
    ESP.find('\n');
    ESP.println("set user myname");
    ESP.find('\n');
    ESP.println("set pass mypass");
}

void loop() {
    ESP.print("pub analog/read/0 ");
    ESP.println(analogRead(0));
    ESP.find('\n');

    ESP.print("pub analog/read/1 ");
    ESP.println(analogRead(1));
    ESP.find('\n');

    ESP.print("pub analog/read/2 ");
    ESP.println(analogRead(2));
    ESP.find('\n');

    ESP.print("pub analog/read/3 ");
    ESP.println(analogRead(3));
    ESP.find('\n');

    ESP.print("pub analog/read/4 ");
    ESP.println(analogRead(4));
    ESP.find('\n');

    ESP.print("pub analog/read/5 ");
    ESP.println(analogRead(5));
    ESP.find('\n');

    delay(5000);
}