How to subscribe to multiple variables using ESP32 mqtt and what is the difference between things.ubidots and industrial.ubidots ?
Good day @khaledmohsen1400 ,
Thank you for sharing your question with the community.
To subscribe to any topic via MQTT, please refer to our hardware documentation, where you will find examples. Now, our official URL is industrial.api.ubidots.com. The URL things.ubidots.com was used in our Ubidots for education platform that was shut down a couple of months ago and replace for Ubidots STEM, which offers an experience closer to Ubidots licenses., It has improved reliability compared to its predecessor. In summary to send and retrieve data you should always use industrial.api.ubidots.com.
All the best,
-Isabel
Hello @khaledmohsen1400
Ubidots has just released a MQTT library for the ESP32 that will ease your code programming to interact with the MQTT broker, both for publishing data and/or subscribing to it. I suggest:
- Following in the below guide:
- Read the Docs and Example in the Github repository to have a better feeling about the library operation.
At last, the below code will help you:
- Subscribe to the last value of 10 different relay variables in a Device labeled as “esp32”. You should change the device and variables labels according to your own.
- The
callback()function will receive the data and parse the variable label out of the subscription topic so you know which variable changed. - Based on the variable label, the
execute_cases()function will print the value based on its switch case.
#include "UbidotsEsp32Mqtt.h"
/****************************************
Define Constants
****************************************/
#define WIFISSID "" // Put your WifiSSID here
#define PASSWORD "" // Put your wifi password here
#define TOKEN "" // Put your Ubidots' TOKEN
#define VARIABLE_LABEL_SUB_1 "relay" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_2 "relay2" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_3 "relay3" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_4 "relay4" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_5 "relay5" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_6 "relay6" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_7 "relay7" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_8 "relay8" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_9 "relay9" // Assing the variable label to subscribe
#define VARIABLE_LABEL_SUB_10 "relay10" // Assing the variable label to subscribe
#define DEVICE_LABEL "esp32" // Assig the device label to subscribe
#define R1 15
#define R2 2
#define R3 4
#define R4 18
#define R5 19
#define R6 21
#define R7 22
#define R8 23
#define R9 32
#define R10 33
const uint8_t NUMBER_OF_VARIABLES = 10; // Number of variable to subscribe to
char *variable_labels[NUMBER_OF_VARIABLES] = {"relay", "relay2", "relay3", "relay4", "relay5", "relay6", "relay7", "relay8", "relay9", "relay10"}; // labels of the variable to subscribe to
float CONTROL1; // Name of the variable to be used within the code.
float CONTROL2; // Name of the variable to be used within the code.
float CONTROL3; // Name of the variable to be used within the code.
float CONTROL4; // Name of the variable to be used within the code.
float CONTROL5; // Name of the variable to be used within the code.
float CONTROL6; // Name of the variable to be used within the code.
float CONTROL7; // Name of the variable to be used within the code.
float CONTROL8; // Name of the variable to be used within the code.
float CONTROL9; // Name of the variable to be used within the code.
float CONTROL10; // Name of the variable to be used within the code.
float value; // To store incoming value.
uint8_t variable; // To keep track of the state machine and be able to use the switch case.
const int ERROR_VALUE = 65535; // Set here an error value
/****************************************
Initializate constructors for objects
****************************************/
Ubidots ubidots(TOKEN);
/****************************************
Auxiliar Functions
****************************************/
void callback(char *topic, byte *payload, unsigned int length)
{
char *variable_label = (char *)malloc(sizeof(char) * 30);
get_variable_label_topic(topic, variable_label);
Serial.println(variable_label);
value = btof(payload, length);
set_state(variable_label);
execute_cases();
free(variable_label);
}
// Parse topic to extract the variable label which changed value
void get_variable_label_topic(char *topic, char *variable_label)
{
Serial.print("topic:");
Serial.println(topic);
sprintf(variable_label, "");
for (int i = 0; i < NUMBER_OF_VARIABLES; i++)
{
char *result_lv = strstr(topic, variable_labels[i]);
if (result_lv != NULL)
{
uint8_t len = strlen(result_lv);
char result[100];
uint8_t i = 0;
for (i = 0; i < len - 3; i++)
{
result[i] = result_lv[i];
}
result[i] = '\0';
Serial.print("Label is: ");
Serial.println(result);
sprintf(variable_label, "%s", result);
break;
}
}
}
// cast from an array of chars to float value.
float btof(byte *payload, unsigned int length)
{
char *demo_ = (char *)malloc(sizeof(char) * 10);
for (int i = 0; i < length; i++)
{
demo_[i] = payload[i];
}
return atof(demo_);
}
// State machine to use switch case
void set_state(char *variable_label)
{
variable = 0;
for (uint8_t i = 0; i < NUMBER_OF_VARIABLES; i++)
{
if (strcmp(variable_label, variable_labels[i]) == 0)
{
break;
}
variable++;
}
if (variable >= NUMBER_OF_VARIABLES)
variable = ERROR_VALUE; // Not valid
}
// Function with switch case to determine which variable changed and assigned the value accordingly to the code variable
void execute_cases()
{
switch (variable)
{
case 0:
CONTROL1 = value;
// digitalWrite(R1, value);
Serial.print("CONTROL1: ");
Serial.println(CONTROL1);
Serial.println();
break;
case 1:
CONTROL2 = value;
// digitalWrite(R2, value);
Serial.print("CONTROL2: ");
Serial.println(CONTROL2);
Serial.println();
break;
case 2:
CONTROL3 = value;
// digitalWrite(R3, value);
Serial.print("CONTROL3: ");
Serial.println(CONTROL3);
Serial.println();
break;
case 3:
CONTROL4 = value;
// digitalWrite(R4, value);
Serial.print("CONTROL3: ");
Serial.println(CONTROL3);
Serial.println();
break;
case 4:
CONTROL5 = value;
// digitalWrite(R5, value);
Serial.print("CONTROL5: ");
Serial.println(CONTROL5);
Serial.println();
break;
case 5:
CONTROL6 = value;
// digitalWrite(R6, value);
Serial.print("CONTROL6: ");
Serial.println(CONTROL6);
Serial.println();
break;
case 6:
CONTROL7 = value;
// digitalWrite(R7, value);
Serial.print("CONTROL7: ");
Serial.println(CONTROL7);
Serial.println();
break;
case 7:
CONTROL8 = value;
// digitalWrite(R8, value);
Serial.print("CONTROL8: ");
Serial.println(CONTROL8);
Serial.println();
break;
case 8:
CONTROL9 = value;
// digitalWrite(R9, value);
Serial.print("CONTROL9: ");
Serial.println(CONTROL9);
Serial.println();
break;
case 9:
CONTROL10 = value;
// digitalWrite(R10, value);
Serial.print("CONTROL10: ");
Serial.println(CONTROL10);
Serial.println();
break;
case ERROR_VALUE:
Serial.println("error");
Serial.println();
break;
default:
Serial.println("default");
Serial.println();
}
}
/****************************************
Main Functions
****************************************/
void setup()
{
Serial.begin(115200);
pinMode(R1, OUTPUT);
pinMode(R2, OUTPUT);
pinMode(R3, OUTPUT);
pinMode(R4, OUTPUT);
pinMode(R5, OUTPUT);
pinMode(R6, OUTPUT);
pinMode(R7, OUTPUT);
pinMode(R8, OUTPUT);
pinMode(R9, OUTPUT);
pinMode(R10, OUTPUT);
// ubidots.setDebug(true); // uncomment this to make debug messages available
ubidots.connectToWifi(WIFISSID, PASSWORD);
ubidots.setCallback(callback);
ubidots.setup();
ubidots.reconnect();
for (uint8_t i = 0; i < NUMBER_OF_VARIABLES; i++)
{
ubidots.subscribeLastValue(DEVICE_LABEL, variable_labels[i]); // Insert the device and Variable's Labels
delay(100);
}
}
void loop()
{
if (!ubidots.connected())
{
ubidots.reconnect();
for (uint8_t i = 0; i < NUMBER_OF_VARIABLES; i++)
{
ubidots.subscribeLastValue(DEVICE_LABEL, variable_labels[i]); // Insert the device and Variable's Labels
delay(100);
}
}
ubidots.loop();
}
Best,
D