ESP8266 SSID String to a char* -- HOW?

Projects Programming
1

Hey falks,

why is so difficult to convert a String, to a char* :confused: I searched the whole internet and found nothing.

I have an ESP8266. I am using a String for the SSID of the ESP. This is the original code to connect the ESP to my router:

char* ssid = "Netgear";
char* password = "redacted";

WiFi.begin(ssid,password);

I have stored the ssid in a file via SPIFFS. The file is read as a string, like this:

File f = SPIFFS.open("/ssid.txt", "r");
String SatzSSID=f.readStringUntil('\n');  // this String is the SSID

It has to be a char* in the WiFi.begin();

Therefore, I have to convert it from STring, to a char*

How can I do it in the simpliest way ?

2

A String has a function named c_str that does this. In your case SatzSSID.c_str() should do the trick.

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3

That would be "SatzSSID.c_str()", wouldn't it?
"password" is a simple C string, and has no member functions.

The whole Internet except the most obvious part, the language reference.

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4

That is a better example, yes. OP has not mentioned what the name of the new password variable is. I updated my reply, thanks.

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5

thanks, will try it later in the evening ;D

I just came home from night-shift (Germany) :smiley:

6

Hmm... you might want to include some more useful search terms... the Internet has quite a lot of useful stuff.

https://www.google.com/search?q=convert+string+c+string+arduino

7 
// the SSID is stored in the ip.txt as following:
// %1%Netgear%1q2w3e4r
File n = SPIFFS.open("/ssid.txt", "r");
String FileContent=n.readStringUntil('\n');


// the followig Part splits the content with a deleminiter '%'
index1 = FileContent.indexOf('%');
index2 = FileContent.indexOf('%', index1+1);
index3 = FileContent.indexOf('%', index2+1);
index4 = FileContent.indexOf('%', index3+1);
StringA = FileContent.substring(index1+1, index2);
StringB = FileContent.substring(index2+1, index3); // <-- the SSID
StringC = FileContent.substring(index3+1, index4); // <-- the passwd


char* ssid = StringB .c_str();
char* password = StringC .c_str();
  
WiFi.begin(StringB,StringB);

It still does not work. The Errormessage is:

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

8

Should this not be:

WiFi.begin(ssid, password);
9

Like that?

10

yes, but that is only a name of variables... so does the name of a variable matter ? wait, will try.

11

The name does not matter, but in the snippet you shared, StringB is of type String.

12

yeah, at the top I used another name for this variable. Just changed it to show you the other parts of the could.

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