A simple arduino library provisioning a client to connect with Cloud Providers, via MQTT. It is looking for agnostic connection.
This library is based on other amazing projects, for MQTT connection PubSubClient is included. The connection should be secured with your cloud providers, to get current time NTPClient is also included.
- Azure (IoT Hub), using MQTT and X.509 as authentication
You must include AlmaviosLitMqtt.h to use the library, the below code is the representation of a basic connection with Azure. This example uses x.509 as authentication, so you must have a cert and key file.
The CN of the certification will be the same of your IoT device. The CA cert must be in the Azure hub, otherwise the connection will be refused. In future versions, we will allow SAS connection. Your cert and key file must be provided to LitCloudProvider, we recommend for development openssl to get it in binary form.
Nowadays, AlmaviosLitMqtt have a basic support using arduino of ESP32 and ESP8266. This project aims agnostic connection to cloud providers, but to be almost play-and-plug we are trying to reduce the over configuration for each supported container(board).
An example using ESP8266 with Arduino, version 2.5.2 of the boards. The certs will be in binary form
#include <AlmaviosLitMqtt.h>
#include "certs.h"
#define SSID_ "YourWifiSSID"
#define PASSWORD_ "writeyourpassword"
void setup(){
Serial.begin(115200);
LitCloudAzure.begin(
"nameofyourhub", "yourdeviceid",
device_crt, device_crt_len,
device_key, device_key_len
);
LitMqtt.begin(SSID_, PASSWORD_, LitCloudAzure);
}
void loop(){
LitMqtt.run();
// ...
LitMqtt.publish("An important message");
}An example using ESP32 with Arduino, version 1.0.4 of the boards. The certs will be const char*
#include <AlmaviosLitMqtt.h>
#include "certs.h"
#define SSID_ "YourWifiSSID"
#define PASSWORD_ "writeyourpassword"
void setup(){
Serial.begin(115200);
LitCloudAzure.begin( "nameofyourhub", "yourdeviceid", device_crt, device_key);
LitMqtt.begin(SSID_, PASSWORD_, LitCloudAzure);
}
void loop(){
LitMqtt.run();
// ...
LitMqtt.publish("An important message");
}All the examples show below, are using the same parent structure. It does not matter the cloud provider or container you are using, the code will be the same. For simplicity, the snippets are from the sendMsg() function.
As you can see in the below code, Azure provider is being used, you can replace it without a problem in the setup.
#include <AlmaviosLitMqtt.h>
#include "certs.h"
#define SSID_ "YourWifiSSID"
#define PASSWORD_ "writeyourpassword"
long lastMsg = 0;
void setup(){
// Feel free to setup your cloud provider
Serial.begin(115200);
LitCloudAzure.begin( "nameofyourhub", "yourdeviceid", device_crt, device_key);
LitMqtt.begin(SSID_, PASSWORD_, LitCloudAzure);
}
void sendMsg(){
// {{ The magic occurs here }}
}
void loop(){
LitMqtt.run();
long now = millis();
if (now - lastMsg > 16000) {
lastMsg = now;
sendMsg();
}
} All the magic is inside the publish common method. The default topic, you can not change it yet, is in the form asked by your provider. Therefore, your code will be easier to read and you can focus on other important things. Nowadays the support types are String, std::string, int, float, double and boolean.
LitMqtt.publish(555);
// Or
LitMqtt.publish("555");The boolean output will be true and false. All the data is parsed to ASCII characters, we are still working to handle it in binary form; it is important if you are looking to reduce the weight of each message.
If you are looking to send multiple attributes, you can format your data manually. LitMqtt helps you with a simple format CSV. In this format, the values are separeted by commas. You can reach this format using an array and our helper method publishCSV(). For this publisher, you have two options, create the array outside the method or be explicit with the method.
The external path, you can create an array with the supported types(the same as publish)
float values[] = {speed, 30.2, ..., light};
LitMqtt.publishCSV(values);The next option, avoid the creation of a variable, but you need to write the datatype and the array length.
LitMqtt.publishCSV<bool,4>({0, 4, false, true});If the length does not correspond with the written number, an error can be throw be the IDE.
JSON is a format more complex than CSV, it is easier for humans to read and many computer languages support it. It contains plain characteres, so it is not as optimized as other solutions, the advantage is we can send data without rememering the order stablished in our cloud provider. AlmaviosLitMqtt has a basic support for it.
There are only supported plain objects, the datatypes are the same from publish, they included to the keys and the values. As a note, all the keys are transformed to JSON strings. In another hand, you can use publishJSON() as external or explicit.
External, the arrays must be from the same size, and previous variables are required
float values[] = {temperature, humidity, ..., light, 50.34};
String keys[] = {"temp_key", "humidity", ..., "light", "other"};
LitMqtt.publishJSON(values, keys);Explicit, no variables are required, but you have to provide the datatype of the values, the datatype of the keys and the lenght of the arrays(same for both of them)
LitMqtt.publishJSON<float, String, 4>({temperature, humidity, light, 50.34}, {"temp_key", "humidity", "light", "other"});