I'm trying to upload the code from here to work with an ESP8266. So I copy/pasted the code to the Arduino IDE and I get this error:

C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFi.h:79:9: error: initializing argument 1 of 'int WiFiClass::begin(char*, const char*)' [-fpermissive]

int begin(char* ssid, const char *passphrase); ^

exit status 1 invalid conversion from 'const char*' to 'char*' [-fpermissive]

Can anyone help me with this?


This begin() method expects a modifiable character array as its first argument. That's what you should provide:

char ssid[]           = "YOUR_SSID";      // this is changed
const char* password  = "YOUR_PASSWORD";  // this is fine
WiFi.begin(ssid, password);
  • When I try to upload it I get: warning: espcomm_sync failed error: espcomm_open failed. Do you know if it is from the code? – Physther Jun 21 '17 at 20:04
  • @Physther: I don't know. It's ESP specific and I have no experience with those devices. But see this GitHub issue – Edgar Bonet Jun 21 '17 at 20:18
  • Regarding the espcomm_sync failed error, see github.com/esp8266/Arduino/blob/master/doc/faq/… – per1234 Jun 22 '17 at 0:41
  • It's more likely that the WiFi library is simply unwise in its declaration. There's no real need for the ssid argument to be mutable - the ssid and passphrase are in fact treated identically internally. – Chris Stratton Nov 4 '17 at 19:25

The location where you are calling the function begin, has as first parameter a parameter of type const char* instead of char* ... remove the const from this argument type.

Probably you have something like

const char* s = ....


...begin(s, ...)

Change class s to

char* s = ...
  • The same question as for Edgar. Can this: warning: espcomm_sync failed error: espcomm_open failed be caused by the code? – Physther Jun 21 '17 at 20:06
  • It could be ... I have also no experience with them like Edgar Bonet. Trace back where you call the function that fails and check the parameter values (and compare it to examples). – Michel Keijzers Jun 21 '17 at 21:21

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