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

code: [select]

#include <esp_adafruit_ssd1306.h>
#include <avr/pgmspace.h>
#include <softwareserial.h>
#include <wire.h>
#include <adafruit_gfx.h>

#define oled_reset 4
adafruit_ssd1306 display(oled_reset);
#if (ssd1306_lcdheight != 64)
#error("height incorrect, please fix adafruit_ssd1306.h!");
#endif

#define debug true

softwareserial esp8266(2, 3); // make rx arduino line pin 2, make tx arduino line pin 3.
// means need connect tx line esp arduino's pin 2
// , rx line esp arduino's pin 3
void setup()
{
  display.begin(ssd1306_switchcapvcc, 0x3c);  // initialize i2c addr 0x3d (for 128x64)

  display.cleardisplay();
  delay(5000);


  serial.begin(9600);
  esp8266.begin(9600); // esp's baud rate might different

  pinmode(11, output);
  digitalwrite(11, low);

  pinmode(12, output);
  digitalwrite(12, low);

  pinmode(13, output);
  digitalwrite(13, low);

  pinmode(10, output);
  digitalwrite(10, low);

  char atreset[11] progmem = "at+rst\r\n";
  char atcwmode[17] progmem = "at+cwmode=1\r\n";
  char atcwjap[37] progmem = "at+cwjap=\"rajahome\",\"rama2869\"\r\n";
  char atcifsr[13] progmem = "at+cifsr\r\n";
  char atcipmux[17] progmem = "at+cipmux=1\r\n";
  char atcipserver[22] progmem = "at+cipserver=1,80\r\n";

  sendcommand(atreset, 2000, debug); // reset module
  sendcommand(atcwmode, 2000, debug); // configure access point
  sendcommand(atcwjap, 3000, debug);
  delay(10000);
  sendcommand(atcifsr, 3000, debug); // ip address
  sendcommand(atcipmux, 1000, debug); // configure multiple connections
  sendcommand(atcipserver, 1000, debug); // turn on server on port 80

  serial.println(f("server ready"));
}

void loop()
{
  if (esp8266.available()) // check if esp sending message
  {


    if (esp8266.find("+ipd,"))
    {
      delay(1000); // wait serial buffer fill (read serial data)
      // connection id can disconnect
      int connectionid = esp8266.read() - 48; // subtract 48 because read() function returns
      // ascii decimal value , 0 (the first decimal number) starts @ 48

      esp8266.find("pin="); // advance cursor "pin="

      int pinnumber = (esp8266.read() - 48); // first number i.e. if pin 13 1st number 1
      int secondnumber = (esp8266.read() - 48);
      if (secondnumber >= 0 && secondnumber <= 9)
      {
        pinnumber *= 10;
        pinnumber += secondnumber; // second number, i.e. if pin number 13 2nd number 3, add first number
      }

      digitalwrite(pinnumber, !digitalread(pinnumber)); // toggle pin

      // build string send device requesting pin toggle
      char content[15] progmem="pin ";
      char pin[1] progmem={48};
      strcat(content,pin);
      strcat(content,"is");

      if (digitalread(pinnumber))
      {
        strcat(content,"on");
      }
      else
      {
        strcat(content,"off");
      }

      sendhttpresponse(connectionid, content);

      char closecommand[16] progmem = "at+cipclose=";
      // make close command
      char cid[2] progmem = {48}; //ascii value of 0 48

      strcat(closecommand, cid); //append connectionid
      strcat(closecommand, "\r\n");

      sendcommand(closecommand, 1000, debug); // close connection
    }
  }
}

/*
  name: senddata
  description: function used send data esp8266.
  params: command - data/command send; timeout - time wait response; debug - print serial window?(true = yes, false = no)
  returns: response esp8266 (if there reponse)
*/
char senddata(char command[], const int timeout, boolean debug)
{
  char response[100] progmem = "";

  int datasize = strlen(command);
  char data[datasize] progmem;
  //command.tochararray(data, datasize);

  esp8266.write(data, datasize); // send read character esp8266
  if (debug)
  {
    serial.println("\r\n====== http response arduino ======");
    serial.write(data, datasize);
    serial.println("\r\n========================================");
  }

  long int time = millis();

  while ( (time + timeout) > millis())
  {
    while (esp8266.available())
    {

      // esp has data display output serial window
      char c progmem= esp8266.read(); // read next character.
      strcat(response,c);
    }
  }

  if (debug)
  {
    serial.print(response);
  }

  return response;
}

/*
  name: sendhttpresponse
  description: function sends http 200, html utf-8 response
*/
void sendhttpresponse(int connectionid, char content[])
{
  contentlen=strlen(content);
  // build http response
  char httpresponse[100] progmem;
  char httpheader[100] progmem;
  // http header
  strcat(httpheader,"http/1.1 200 ok\r\ncontent-type: text/html; charset=utf-8\r\n");
  strcat(httpheader,"content-length: ");
  strcat(httpheader,contentlen);
  strcat(httpheader,"\r\n");
  strcat(httpheader,"connection: close\r\n\r\n");
 
  httpresponse = strcat(httpheader,content," "); // there bug in code: last character of "content" not sent, cheated adding space
  sendcipdata(connectionid, httpresponse);
}

/*
  name: sendcipdata
  description: sends cipsend=<connectionid>,<data> command

*/
void sendcipdata(int connectionid, char data[])
{
  char cipsend[40] progmem = "at+cipsend=";
  char cid[2]progmem = {48};
  datalen=strlen(data)
  strcat(cipsend, cid);
  strcat(cipsend, ",");
  strcat(cipsend,datalen));
  strcat(cipsend, "\r\n");
  sendcommand(cipsend, 1000, debug);
  senddata(data, 1000, debug);
}

/*
  name: sendcommand
  description: function used send data esp8266.
  params: command - data/command send; timeout - time wait response; debug - print serial window?(true = yes, false = no)
  returns: response esp8266 (if there reponse)
*/
char sendcommand(char command[], const int timeout, boolean debug)
{
  char response[50] progmem = "";

  esp8266.print(command); // send read character esp8266

  long int time = millis();

  while ( (time + timeout) > millis())
  {
    while (esp8266.available())
    {

      // esp has data display output serial window
      char c = esp8266.read(); // read next character.
      response += c;
    }
  }

  if (debug)
  {
    delay(2000);
    // text display tests
    display.settextsize(1);
    display.settextcolor(white);
    display.setcursor(0, 0);
    display.print(response);
    display.display();


    // clear buffer.
    display.cleardisplay();;
  }

  return response;
}

and error
c:\users\user\documents\arduino\espcontrll\espcontrll.ino: in function 'char senddata(char*, int, boolean)':

espcontrll:144: error: invalid conversion 'char' 'const char*' [-fpermissive]


i optimized code  something not working had used  c-string instead of string class  to save ram usage still not going right can me these

code: [select]

char response[50] progmem = "";good luck adding that.

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