Hi can anyone hel me with this? I'm trying to add another device_token with a same variables but I always gets an error. I'm trying to add const char*

Projects Programming
1 
#include <SPI.h>
#include <MFRC522.h>
//NodeMCU--------------------------
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
//************************************************************************
#define SS_PIN  D2  //D2
#define RST_PIN D1  //D1
//************************************************************************
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance.
//************************************************************************
/* Set these to your desired credentials. */
const char *ssid = "wifi";
const char *password = "123456789";
const char* device_token  = "c93080ec3f675356"; 
//************************************************************************
String URL = "http://192.168.101.8/rfidattendance/getdata.php"; //computer IP or the server domain
String getData, Link;
String OldCardID = "";
unsigned long previousMillis = 0;
//************************************************************************
void setup() {
  delay(1000);
  Serial.begin(9600);
  SPI.begin();  // Init SPI bus
  mfrc522.PCD_Init(); // Init MFRC522 card
  //---------------------------------------------
  connectToWiFi();
}
//************************************************************************
void loop() {
  //check if there's a connection to Wi-Fi or not
  if(!WiFi.isConnected()){
    connectToWiFi();    //Retry to connect to Wi-Fi
  }
  //---------------------------------------------
  if (millis() - previousMillis >= 15000) {
    previousMillis = millis();
    OldCardID="";
  }
  delay(50);
  //---------------------------------------------
  //look for new card
  if ( ! mfrc522.PICC_IsNewCardPresent()) {
    return;//got to start of loop if there is no card present
  }
  // Select one of the cards
  if ( ! mfrc522.PICC_ReadCardSerial()) {
    return;//if read card serial(0) returns 1, the uid struct contians the ID of the read card.
  }
  String CardID ="";
  for (byte i = 0; i < mfrc522.uid.size; i++) {
    CardID += mfrc522.uid.uidByte[i];
  }
  //---------------------------------------------
  if( CardID == OldCardID ){
    return;
  }
  else{
    OldCardID = CardID;
  }
  //---------------------------------------------
//  Serial.println(CardID);
  SendCardID(CardID);
  delay(1000);
}
//************send the Card UID to the website*************
void SendCardID( String Card_uid ){
  Serial.println("Sending the Card ID");
  if(WiFi.isConnected()){
    HTTPClient http;    //Declare object of class HTTPClient
    //GET Data
    getData = "?card_uid=" + String(Card_uid) + "&device_token=" + String(device_token); // Add the Card ID to the GET array in order to send it
    //GET methode
    Link = URL + getData;
    http.begin(Link); //initiate HTTP request   //Specify content-type header
    
    int httpCode = http.GET();   //Send the request
    String payload = http.getString();    //Get the response payload

//    Serial.println(Link);   //Print HTTP return code
    Serial.println(httpCode);   //Print HTTP return code
    Serial.println(Card_uid);     //Print Card ID
    Serial.println(payload);    //Print request response payload

    if (httpCode == 200) {
      if (payload.substring(0, 5) == "login") {
        String user_name = payload.substring(5);
    //  Serial.println(user_name);

      }
      else if (payload.substring(0, 6) == "logout") {
        String user_name = payload.substring(6);
    //  Serial.println(user_name);
        
      }
      else if (payload == "succesful") {

      }
      else if (payload == "available") {

      }
      delay(100);
      http.end();  //Close connection
    }
  }
}
//********************connect to the WiFi******************
void connectToWiFi(){
    WiFi.mode(WIFI_OFF);        //Prevents reconnection issue (taking too long to connect)
    delay(1000);
    WiFi.mode(WIFI_STA);
    Serial.print("Connecting to ");
    Serial.println(ssid);
    WiFi.begin(ssid, password);
    
    while (WiFi.status() != WL_CONNECTED) {
      delay(500);
    }
    Serial.println("");
    Serial.println("Connected With Wi-Fi");
  
    Serial.print("IP address: ");
    Serial.println(WiFi.localIP());  //IP address assigned to your ESP
    
    delay(1000);
}
2

I'm trying to add another const char*

3

Welcome and thanks for using code tags in your first post :+1:

Please post the complete error message (again using code tags).

It does not sound like you have a problem with the IDE but a programming problem; hence your topic has been moved.

1 Like
4

I don't have error in the code but I want to declare another const char* device_token = " " with the same variables.

5

The simplest way would be something like

const char* device_token  = "c93080ec3f675356"; 
const char* device_token2  = "12345";

This however is not scalable and it would be better to use arrays; something like

const char* device_token[]  = 
{
  "c93080ec3f675356",
  "12345",
};

I suggest that you read up on arrays if you're not familiar with them.

6

hello sir sterretje. I'm getting an error like this
C\Users\ASUS\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266/WString.h:57:9: note: String::String(const String&)
String(const String &str);
^
C:\Users\ASUS\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266/WString.h:57:9: note: no known conversion for argument 1 from 'const char* [2]' to 'const String&'

exit status 1

Compilation error: call of overloaded 'String(const char* [2])' is ambiguous

7

Please post your updated code (in a new reply).

8 
#include <SPI.h>
#include <MFRC522.h>
//NodeMCU--------------------------
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
//************************************************************************
#define SS_PIN  D2  //D2
#define RST_PIN D1  //D1
//************************************************************************
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance.
//************************************************************************
/* Set these to your desired credentials. */
const char *ssid = "wifi";
const char *password = "123456789";
const char* device_token  = "c93080ec3f675356"; 
const char* device_token2 = "424b8af2d53545cd"
//************************************************************************
String URL = "http://192.168.101.8/rfidattendance/getdata.php"; //computer IP or the server domain
String getData, Link;
String OldCardID = "";
unsigned long previousMillis = 0;
//************************************************************************
void setup() {
  delay(1000);
  Serial.begin(9600);
  SPI.begin();  // Init SPI bus
  mfrc522.PCD_Init(); // Init MFRC522 card
  //---------------------------------------------
  connectToWiFi();
}
//************************************************************************
void loop() {
  //check if there's a connection to Wi-Fi or not
  if(!WiFi.isConnected()){
    connectToWiFi();    //Retry to connect to Wi-Fi
  }
  //---------------------------------------------
  if (millis() - previousMillis >= 15000) {
    previousMillis = millis();
    OldCardID="";
  }
  delay(50);
  //---------------------------------------------
  //look for new card
  if ( ! mfrc522.PICC_IsNewCardPresent()) {
    return;//got to start of loop if there is no card present
  }
  // Select one of the cards
  if ( ! mfrc522.PICC_ReadCardSerial()) {
    return;//if read card serial(0) returns 1, the uid struct contians the ID of the read card.
  }
  String CardID ="";
  for (byte i = 0; i < mfrc522.uid.size; i++) {
    CardID += mfrc522.uid.uidByte[i];
  }
  //---------------------------------------------
  if( CardID == OldCardID ){
    return;
  }
  else{
    OldCardID = CardID;
  }
  //---------------------------------------------
//  Serial.println(CardID);
  SendCardID(CardID);
  delay(1000);
}
//************send the Card UID to the website*************
void SendCardID( String Card_uid ){
  Serial.println("Sending the Card ID");
  if(WiFi.isConnected()){
    HTTPClient http;    //Declare object of class HTTPClient
    //GET Data
    getData = "?card_uid=" + String(Card_uid) + "&device_token=" + String(device_token),  "&id=" + String(id);** // Add the Card ID to the GET array in order to send it

    //GET methode
    Link = URL + getData;
    http.begin(Link); //initiate HTTP request   //Specify content-type header
    
    int httpCode = http.GET();   //Send the request
    String payload = http.getString();    //Get the response payload

//    Serial.println(Link);   //Print HTTP return code
    Serial.println(httpCode);   //Print HTTP return code
    Serial.println(Card_uid);     //Print Card ID
    Serial.println(payload);    //Print request response payload

    if (httpCode == 200) {
      if (payload.substring(0, 5) == "login") {
        String user_name = payload.substring(5);
    //  Serial.println(user_name);

      }
      else if (payload.substring(0, 6) == "logout") {
        String user_name = payload.substring(6);
    //  Serial.println(user_name);
        
      }
      else if (payload == "succesful") {

      }
      else if (payload == "available") {

      }
      delay(100);
      http.end();  //Close connection
    }
  }
}
//********************connect to the WiFi******************
void connectToWiFi(){
    WiFi.mode(WIFI_OFF);        //Prevents reconnection issue (taking too long to connect)
    delay(1000);
    WiFi.mode(WIFI_STA);
    Serial.print("Connecting to ");
    Serial.println(ssid);
    WiFi.begin(ssid, password);
    
    while (WiFi.status() != WL_CONNECTED) {
      delay(500);
    }
    Serial.println("");
    Serial.println("Connected With Wi-Fi");
  
    Serial.print("IP address: ");
    Serial.println(WiFi.localIP());  //IP address assigned to your ESP
    
    delay(1000);
}
9

here is the updated

10

Missing something here in the second line:

const char* device_token  = "c93080ec3f675356"; 
const char* device_token2 = "424b8af2d53545cd"

a7

11

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