invalid conversion from 'int' to 'char*' [-fpermissive]

Using Arduino Programming Questions
1

Please help me solve this error

my code:
#include "FS.h"
#include <ESP8266WiFi.h>
#include <PubSubClient.h>// allows you to send and receive mqtt messages
#include <NTPClient.h> // include time information from the internet
#include <WiFiUdp.h>

int Gas_analog = A0; // used for ESP8266
int Gas_digital = D1; // used for ESP8266

// Update these with values suitable for your network.

const char* ssid = "dg1";
const char* password = "Ashi@98563";

WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, "pool.ntp.org");

const char* AWS_endpoint = "arufwoersqlu4-ats.iot.us-east-2.amazonaws.com"; //MQTT broker ip

void callback(char* topic, byte* payload, unsigned int length) {
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i < length; i++) {
Serial.print((char)payload*);*
}
Serial.println();
}
WiFiClientSecure espClient;
PubSubClient client(AWS_endpoint, 8883, callback, espClient); //set MQTT port number to 8883 as per //standard
#define BUFFER_LEN 256
char msg[BUFFER_LEN];
long lastMsg = 0;
int value = 0;
byte mac[6];
char mac_Id[18];
void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
espClient.setBufferSizes(512, 512);
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
timeClient.begin();
while(!timeClient.update()){
timeClient.forceUpdate();
}
espClient.setX509Time(timeClient.getEpochTime());
}
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Attempt to connect
if (client.connect("ESPthing")) {
Serial.println("connected");
// Once connected, publish an announcement...
client.publish("outTopic", "hello");
// ... and resubscribe
client.subscribe("inTopic");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
char buf[256];
espClient.getLastSSLError(buf,256);
Serial.print("WiFiClientSecure SSL error: ");
Serial.println(buf);
// Wait 5 seconds before retrying
delay(5000);
}
}
}
void setup() {

  • Serial.begin(115200); *
  • pinMode(Gas_digital, INPUT);*
  • Serial.setDebugOutput(true);*

setup_wifi();
delay(1000);
if (!SPIFFS.begin()) {
Serial.println("Failed to mount file system");
return;
}
Serial.print("Heap: "); Serial.println(ESP.getFreeHeap());
// Load certificate file
*File cert = SPIFFS.open("/cert.der", "r"); *
if (!cert) {
Serial.println("Failed to open cert file");
}
else
Serial.println("Success to open cert file");
delay(1000);
if (espClient.loadCertificate(cert))
Serial.println("cert loaded");
else
Serial.println("cert not loaded");
// Load private key file
*File private_key = SPIFFS.open("/private.der", "r"); *
if (!private_key) {
Serial.println("Failed to open private cert file");
}
else
Serial.println("Success to open private cert file");
delay(1000);
if (espClient.loadPrivateKey(private_key))
Serial.println("private key loaded");
else
Serial.println("private key not loaded");
// Load CA file
File ca = SPIFFS.open("/ca.der", "r"); //replace ca eith your uploaded file name
if (!ca) {
Serial.println("Failed to open ca ");
}
else
Serial.println("Success to open ca");
delay(1000);
if(espClient.loadCACert(ca))
Serial.println("ca loaded");
else
Serial.println("ca failed");
Serial.print("Heap: "); Serial.println(ESP.getFreeHeap());
//===========================================================================
WiFi.macAddress(mac);
snprintf(mac_Id, sizeof(mac_Id), "%02x:%02x:%02x:%02x:%02x:%02x",
mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
Serial.print(mac_Id);
//============================================================================
}
//int AirQualityIndex = analogRead(Gas_analog);
//int gassensorDigital = digitalRead(Gas_digital);
int gassensorAnalog = analogRead(Gas_analog);
int gassensorDigital = digitalRead(Gas_digital);
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
long now = millis();
if (now - lastMsg > 2000) {
lastMsg = now;
++value;
String macIdStr = mac_Id;
String airquality = String(gassensorAnalog).c_str();
snprintf (gassensorAnalog, BUFFER_LEN, "{"mac_Id" : "%s", "AirQualityIndex" : %s}", macIdStr.c_str(), airquality.c_str());

  • Serial.print("Gas Sensor: ");*

  • Serial.print(gassensorAnalog);*

  • Serial.print("\t");*

  • Serial.print("Gas Class: ");*

  • Serial.print(gassensorDigital);*

  • Serial.print("\t");*

  • Serial.print("\t");*

  • if (gassensorAnalog > 1000) {*

  • Serial.println("Gas");*

  • }*

  • else {*

  • Serial.println("No Gas");*

  • }*

  • delay(100);*
    }
    client.publish("outTopic", airquality);
    Serial.print("Heap: "); Serial.println(ESP.getFreeHeap()); //Low heap can cause problems
    }

2

Please post your code using code tags according to the forum guidelines:

Read this before posting a programming question ...

Also, it would help to know what line of code the compiler is complaining about.

3

This is a problem:

  for (int i = 0; i < length; i++) {
    Serial.print((char)payload);
  }

Since payload is a byte*. I assume the payload must be ASCII so you should index, dereference and then typecast to char

  for (int i = 0; i < length; i++) {
    Serial.print((char) *(payload + i));
  }
4

ToddL1962:
This is a problem:

  for (int i = 0; i < length; i++) {

Serial.print((char)payload);
 }

The code actually says:

  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }

Because the code was not within code tags, the array indexing was treated as an 'italics' tag.

5

johnwasser:
The code actually says:

  for (int i = 0; i < length; i++) {

Serial.print((char)payload[i]);
 }



Because the code was not within code tags, the array indexing was treated as an 'italics' tag.

It figures...