dtostrf() alternative for concatenating a float and a string

Using Arduino Programming Questions
11

Dear,

I tried all the tips posted above, but none of them worked for me. I put my code below to see if anyone has a suggestion. The problem just seems damn 'float'. Since I can not turn it into string, it does not work my insertion into the database using the library mysql.h.

#include "SPI.h"
#include "Ethernet.h"
#include "sha1.h"
#include "mysql.h"

// Network conf. 
byte mac_addr[] = { 0x54, 0x55, 0x4F, 0x11, 0x0F, 0x2C };
EthernetClient client;
//Server address
IPAddress server_addr(1, 1, 1, 1);

//Data variables
int pinosensor = 0;
int valorlido = 0; 
float temperatura = 0; 
int porta = 8;

//Configuracao da conexao com o arduino
Connector my_conn; // The Connector/Arduino reference

char user[] = "arduino";
char password[] = "arduino";

void read_dados(){
  pinMode(porta, INPUT); 
  //Medidor de Temperatura
  valorlido = analogRead(pinosensor);
  temperatura = (valorlido * 0.00488); 
  temperatura = temperatura * 100; 
  Serial.print("Temperatura atual: ");
  Serial.println(temperatura);
  Serial.print("\n");
}

char *dtostrf (double val, signed char width, unsigned char prec, char *sout) {
  char fmt[20];
  sprintf(fmt, "%%%d.%df", width, prec);
  sprintf(sout, fmt, val);
  return sout;
}

void insert_data(){
 
  //Don't work - this is a test from toppic 103935.0
  String strLab = "Temperatura = ";
  char tmp[10];
  dtostrf(temperatura,1,2,tmp);
  String strOut = strLab + tmp;
  Serial.println(strOut);
  //the result of this serial.println is Temperatura = ?
  
  //Don't work - this is a test from toppic 103935.0
  char voltageMsg[25];
  sprintf(voltageMsg, "Temperatura : %f", temperatura);
  Serial.println(voltageMsg);
  //the result of this serial.println is Temperatura : ?

    
  //Just function 'now()' is inputed correctly in Database
  char buf[256];
  sprintf(buf, "INSERT INTO datacenter.tb_teste (data, temp) VALUES (now(), %d)", temperatura);
  my_conn.cmd_query(buf);

}

void setup() {
  
  // start the serial library:
  Serial.begin(9600);
  // start the Ethernet connection:
  if (Ethernet.begin(mac_addr) == 0) {
    Serial.println("DHCP Failed");
    // no point in carrying on, so do nothing forevermore:
    for(;;)
      ;
  }
  
  // print your local IP address:
  Serial.println(Ethernet.localIP());
  delay(1000);
  //database connection 
  Serial.println("Connecting...");
  if (my_conn.mysql_connect(server_addr, 3306, user, password)){
  delay(500);
      Serial.println("Connected!"); 
    }else{
      Serial.println("Connection failed!");
    }
      
}

void loop() {
  
 read_dados();
 insert_data();
 delay(10000);
  
}//end