publish String in Adafruit IO Moderators: adafruit_support_bill, adafruit

[weal]

I want to Publish string but I got an error, Could you help me?
no matching function for call to 'Adafruit_MQTT_Publish::publish(String&)'

[brubell]

Could you post your entire code below?

[weal]

Code: Select all | TOGGLE FULL SIZE

/***************************************************

#include <ESP8266WiFi.h>
#include "Adafruit_MQTT.h"
#include "Adafruit_MQTT_Client.h"
#include <Arduino.h>
#include <Wire.h>
#include "Adafruit_SHT31.h"

bool enableHeater = false;
uint8_t loopCnt = 0;

Adafruit_SHT31 sht31 = Adafruit_SHT31();
const int AirValue = 520;   //you need to replace this value with Value_1
const int WaterValue = 260;  //you need to replace this value with Value_2
int intervals = (AirValue - WaterValue)/3;
int soilMoistureValue = 0;
/************************* WiFi Access Point *********************************/

#define WLAN_SSID       "************"
#define WLAN_PASS       "*****************"

/************************* Adafruit.io Setup *********************************/

#define AIO_SERVER      "io.adafruit.com"
#define AIO_SERVERPORT  1883                   // use 8883 for SSL
#define AIO_USERNAME    "************"
#define AIO_KEY         "*********************"

/************ Global State (you don't need to change this!) ******************/

// Create an ESP8266 WiFiClient class to connect to the MQTT server.
WiFiClient client;
// or... use WiFiClientSecure for SSL
//WiFiClientSecure client;

// Setup the MQTT client class by passing in the WiFi client and MQTT server and login details.
Adafruit_MQTT_Client mqtt(&client, AIO_SERVER, AIO_SERVERPORT, AIO_USERNAME, AIO_KEY);

/****************************** Feeds ***************************************/

// Setup a feed called 'photocell' for publishing.
// Notice MQTT paths for AIO follow the form: <username>/feeds/<feedname>
Adafruit_MQTT_Publish Sht31_temp = Adafruit_MQTT_Publish(&mqtt, AIO_USERNAME "/feeds/Sht31_temp");
Adafruit_MQTT_Publish Sht31_hum = Adafruit_MQTT_Publish(&mqtt, AIO_USERNAME "/feeds/Sht31_hum");
Adafruit_MQTT_Publish Moisture_state = Adafruit_MQTT_Publish(&mqtt, AIO_USERNAME "/feeds/Moisture_state");
// Setup a feed called 'onoff' for subscribing to changes.
//Adafruit_MQTT_Subscribe onoffbutton = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME "/feeds/onoff");

/*************************** Sketch Code ************************************/

// Bug workaround for Arduino 1.6.6, it seems to need a function declaration
// for some reason (only affects ESP8266, likely an arduino-builder bug).
void MQTT_connect();

void setup() {
  Serial.begin(9600);
  delay(10);
 sht31.begin(0x44);
  Serial.println(F("Adafruit MQTT demo"));
sht31.isHeaterEnabled();
  // Connect to WiFi access point.
  Serial.println(); Serial.println();
  Serial.print("Connecting to ");
  Serial.println(WLAN_SSID);

  WiFi.begin(WLAN_SSID, WLAN_PASS);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println();

  Serial.println("WiFi connected");
  Serial.println("IP address: "); Serial.println(WiFi.localIP());


}

uint32_t x=0;

void loop() {
  // Ensure the connection to the MQTT server is alive (this will make the first
  // connection and automatically reconnect when disconnected).  See the MQTT_connect
  // function definition further below.
  MQTT_connect();

  // this is our 'wait for incoming subscription packets' busy subloop
  // try to spend your time here

 



  // ping the server to keep the mqtt connection alive
  // NOT required if you are publishing once every KEEPALIVE seconds
  /*
  if(! mqtt.ping()) {
    mqtt.disconnect();
  }
  */

 float t = sht31.readTemperature();
  float h = sht31.readHumidity();

  if (! isnan(t)) {  // check if 'is not a number'
    Serial.print("Temp *C = "); Serial.print(t); Serial.print("\t\t");
  } else {
    Serial.println("Failed to read temperature");
  }
 
  if (! isnan(h)) {  // check if 'is not a number'
    Serial.print("Hum. % = "); Serial.println(h);
  } else {
    Serial.println("Failed to read humidity");
  }

//*******************************************************************
String A;
soilMoistureValue = analogRead(A0);  //put Sensor insert into soil

if(soilMoistureValue > WaterValue && soilMoistureValue < (WaterValue + intervals))
{
  Serial.println("Very Wet");
  A="Very Wet";
Moisture_state.publish(A);
}
else if(soilMoistureValue > (WaterValue + intervals) && soilMoistureValue < (AirValue - intervals))
{
  Serial.println("Wet");
  A="Wet";
  Moisture_state.publish(A);
}
else if(soilMoistureValue < AirValue && soilMoistureValue > (AirValue - intervals))
{
  Serial.println("Dry");
  A="Dry";
  Moisture_state.publish(A);
}
delay(100);




//***************************************************************

Sht31_hum.publish(h);
Sht31_temp.publish(t);

}
 
// Function to connect and reconnect as necessary to the MQTT server.
// Should be called in the loop function and it will take care if connecting.
void MQTT_connect() {
  int8_t ret;

  // Stop if already connected.
  if (mqtt.connected()) {
    return;
  }

  Serial.print("Connecting to MQTT... ");

  uint8_t retries = 3;
  while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
       Serial.println(mqtt.connectErrorString(ret));
       Serial.println("Retrying MQTT connection in 5 seconds...");
       mqtt.disconnect();
       delay(5000);  // wait 5 seconds
       retries--;
       if (retries == 0) {
         // basically die and wait for WDT to reset me
         while (1);
       }
  }
  Serial.println("MQTT Connected!");
}


}

[brubell]

The Adafruit MQTT library expects a payload in the following format:

Code: Select all | TOGGLE FULL SIZE

  bool publish(const char *topic, const char *payload, uint8_t qos = 0);

"A" is a string, you'll need to convert it to match the expected const char *payload variable.

[weal]

I still getting an error:
no matching function for call to 'Adafruit_MQTT_Publish::publish(String&)'

[weal]

bool publish(const char *topic, const char *payload, uint8_t qos = 0);

Where/how to use this code?