Converting double to char

Community General Discussion
1

I want make a ESP8266 webserver but I can only send char* format. I need convert double type to char type.

Code:

#include <ESP8266WebServer.h>
#include <SFE_BMP180.h>
#include <Wire.h>
 
const char* ssid = "TTNET_ZTE_2NPS";
const char* password = "mJmZuN6Uwq";
bool success = false;
double T, P;
char status;

ESP8266WebServer server(80);
SFE_BMP180 bmp;

void setup () {
  Serial.begin(115200);
  //BMP180
  bool success = bmp.begin();

  if (success) {
    Serial.println("BMP180 init success");
  }
  else{
    Serial.println("BMP180 FAIL");
  }
  
  //WiFi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println("Bağlandı ");
  Serial.println("IP adresi: ");
  Serial.println(WiFi.localIP());

  //Server
  server.on("/pressure", pressureUpdate);
  
  server.begin();
  Serial.println("HTTP başladı");
}
 
void loop() {
  //BMP180
   bmp.startTemperature();
   bmp.getTemperature(T);
   bmp.startPressure(3);
   bmp.getPressure(P, T);

  //Server
  server.handleClient();
  delay(1000);
  Serial.print("Basınç:");
  Serial.println(P);
}

void pressureUpdate(){
     char *html = to_chars(P);
     server.send(200, "text/html", html);
     delay(100);
     }
2

you need a buffer large enough to host the text, then there are functions to convert a double to its ASCII representation for example:

void pressureUpdate() {
  char html[20];
  snprintf(html, sizeof html, "P = %lf", P);
  server.send(200, "text/html", html);
}
3

This works fine. Thanks for help.

4

have fun !

5

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