Print library value from function on display

Question

I'm trying to print the return value(WiFi.localIP) on my display from the library ESP8266WiFi. But I'm getting an error. For the display I'm using the SSD1306 library.

The purpose of this is to print the IP adress of the ESP8266 on the display.

ERROR:

Arduino: 1.8.16 (Windows 10), Board: "LOLIN(WEMOS) D1 R2 & mini, 80 MHz, Flash, Disabled (new aborts on oom), Disabled, All SSL ciphers (most compatible), 32KB cache + 32KB IRAM (balanced), Use pgm_read macros for IRAM/PROGMEM, 4MB (FS:2MB OTA:~1019KB), v2 Lower Memory, Disabled, None, Only Sketch, 115200"


C:\Users\lauwy\Documents\Arduino\Testsketch\Project\Code\WEB\V4.2\V4.2.ino: In function 'void connectToWifi()':

V4.2:38:32: error: taking address of rvalue [-fpermissive]

   38 |   String ipstat = &WiFi.localIP();

      |                    ~~~~~~~~~~~~^~

V4.2:38:19: error: conversion from 'IPAddress*' to non-scalar type 'String' requested

   38 |   String ipstat = &WiFi.localIP();

      |                   ^~~~~~~~~~~~~~~

exit status 1

taking address of rvalue [-fpermissive]

CODE:

#include <Wire.h>  
#include "SSD1306.h"
SSD1306  display(0x3C, D2, D5);

#include <ESP8266WiFi.h>
const char* ssid     = "*****************"; //Enter network SSID 
const char* password = "*****************"; //Enter network PASSWORD 

WiFiServer server(80);

void connectToWifi(){
  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());

  server.begin();

  String ipstat = &WiFi.localIP();
 
  display.init();
  display.flipScreenVertically();
  display.drawString(0, 0, ipstat);
  display.display();
  
}

hcheung · Accepted Answer · 2021-10-26 04:28:09Z

2

Used toString() method from the ESP8266WiFi library (line 162-173).

String ipstat = WiFi.localIP().toString();

edited Oct 26, 2021 at 4:28

hcheung

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answered Oct 25, 2021 at 19:49

Laurens

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Comments

Cpp_enjoyer · Accepted Answer · 2021-10-25 15:23:40Z

0

2 things:

You are affecting a pointer to initialize a no-pointer variable (with the '&')
The compiler does not manage to cast an object IPAddress in String.

The use of a function "to_string" would be better.

String ipstat = to_string(WiFi.localIP());

Of course you have to code this function if it does not exist ;)

answered Oct 25, 2021 at 15:23

Cpp_enjoyer

11 bronze badge

1 Comment

Juraj Over a year ago

it doesn't exist

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