String Manipulation giving unexpected results

my arduino project electrical monitoring system using: arduino 1 (plus ethernet shield),  voltage , ampere sensors (0-5v), , external server in digitalocean. sketch collect , posts information real time database (influxdb) , representing collected data using grafana. these projects combination, easy use , produce nce result.

mi first test has been collecting voltage inside house, , working charm. time expand adquisition of new variable (amp), , including computation of instant power, , posting information server. @ end have included full arduino sketch.

however 3 variables, having big issues trying build json object has http posted real time database server. unfotunately not expert in processing/c++, find pyhon more string friendly, , lost.

in code trying build json object according influxdb specifications, tried following code 2 variables (vac , iac):

code: [select]

string data;
   data = "[{"
           "\"name\":\"voltamppot\","
           "\"columns\":[\"vacrms\""
                      ",\"iacrms\""
                     // ",\"pac\""
                      "],"
           "\"points\":[[" + string(valuevolt) + ","
                           //+ string(valueamp) + ","
                           //+ string(valuekw) + ","
                      "]]"
           "}]";
    
  serial.println(data);

this working, can deal 2 realtime variables. in example above valuevolt, valueamp , valuekw float elements. result in serial console more or less following:

code: [select]

[{"name":"voltamppot","columns":["vacrms","iacrms"],"points":[[168.91,]]}]
[{"name":"voltamppot","columns":["vacrms","iacrms"],"points":[[145.60,]]}]
[{"name":"voltamppot","columns":["vacrms","iacrms"],"points":[[139.88,]]}]
[{"name":"voltamppot","columns":["vacrms","iacrms"],"points":[[135.92,]]}]
etc

however adding 3 variables (voltage, intensity , power), not working, when print object, string data empty, has not been built.

code: [select]

string data;
   data = "[{"
           "\"name\":\"voltamppot\","
           "\"columns\":[\"vacrms\""
                      ",\"iacrms\""
                      ",\"pac\""
                      "],"
           "\"points\":[[" + string(valuevolt) + ","
                                + string(valueamp) + ","
                                + string(sensoramp) + ","
                           "]]"
           "}]";
    
  serial.println(data);

no results in serial console. why can expand json object include 3 varaibles?, hint?. know there ways concatenate strings, seen in different examples in ide, in way find more direct , clear make later changes.

thank in advanced!


full code, based in thingspeak.com sketch :

code: [select]

// librerias ethernet + http
#include <ethernet.h>
#include <spi.h>

// definicion variables globales
unsigned long tiempo_updatepost = 1*1000; // 1 sg para http post
unsigned long tiempo_updateled = 500;     // 0.5 sg para led
unsigned long previousmillis = 0;
unsigned long currentmillis = 0;

int voltpin = a0;
int sensorvolt = 0; // voltaje integer (0-1023)
float valuevolt = 0.0; // voltaje vacrms (0-450v)  

int amppin = a1;  
int sensoramp = 0 ; // amperaje integer (0-1023)
float valueamp = 0.0; // amperios (0-25a)

float valuekw = 0.0; // kw = volt (450v) x amp (25a) = 11.250 kw

byte mac[] = { 0x90, 0xa2, 0xda, 0x0d, 0xfe, 0xed };

ethernetclient client;
string server[] = "xxxxxx";

long int lastconnectiontime = 0;  
boolean lastconnected = false;
int failedcounter = 0;        

void setup() {
 
  // 1. inicializacin de pins digitales
  //pinmode(ledpin, output);
    
  // 2. inicializacin puerto serie
  serial.begin(9600);
  serial.println("--------------------- setup -------------------");  
  serial.println("");
  serial.println("--- 1. setup: inicializacion serial completada ---");
  serial.println("");
    
  // 3. iniciacion ethernet stack
  startethernet();
  
  serial.println("------------------ fin setup ------------------");  
  serial.println("");
}


void loop () {
  
  // 1. lectura red ethernet
  if (client.available())  
  {
     char c=client.read();
     serial.print(c);
  }
  
  if (!client.connected() && lastconnected) {
     serial.println("...desconectado de red ethernet");
     client.stop();
  }
  
  // 2. calculo de variables / datos postear
  sensorvolt = analogread(voltpin);
  valuevolt = (float(sensorvolt) / 1023.0 ) * 450.0 ; // rango sensor 0-450v
  sensoramp = analogread(amppin);
  valueamp = (float(sensoramp) / 1023.0 ) * 25.0 ; // rango sensor 0-50a
  valuekw = valueamp * valuevolt;
  
   string data;
   data = "[{"
           "\"name\":\"voltamppot\","
           "\"columns\":[\"vacrms\""
                      ",\"iacrms\""
                     // ",\"pac\""
                      "],"
           "\"points\":[[" + string(valuevolt) + ","
                           //+ string(valueamp) + ","
                           //+ string(sensoramp) + ","
                      "]]"
           "}]";
    
  serial.println(data);
  
  // 3. http post :
  
  if (!client.connected() && ((millis() - lastconnectiontime) > tiempo_updatepost))
  {
    updatehttppost(data);  // funcion postea datos servidor
  }
  
  // resetear la conexion internet si ha habido 3 fallos de conexion
  if (failedcounter > 3) {
    failedcounter = 0;
    startethernet();
  }
  
  lastconnected = client.connected();

}

  
/////////////////////////////
// funcion:startethernet() //
/////////////////////////////
void startethernet()
{
  client.stop();
  serial.println("--- 2. setup: startethernet(): conectando red ethernet ...");
  delay(1000);
  
  
  if (ethernet.begin(mac) == 0) {
    serial.println("--- 2. setup: startethernet(): fallo configuracion ethernet ---");
    serial.println("");
  }
  else{
    serial.print("--- 2. setup: startethernet(): conexion dhcp, ip: ");
    serial.print(ethernet.localip());
    serial.println(" ---");
    serial.println();
  }
}


/////////////////////////////
//   funcion: httppost()   //
/////////////////////////////
void updatehttppost(string postdata)
{
  
  if (client.connect("xxxxxxx", 8086)) // conexion servidor
  {
    serial.println("--------------start post-------------------------");
    // cabeceras (http post headers)
    client.print("post /db/test_voltios/series?u=root&p=root http/1.1\n");  
          serial.print("post /db/test_vakw/series?u=root&p=root http/1.1\n");  
    client.println("host: xxxxxx");  
          serial.println("host: xxxxx");  
    client.print("user-agent: arduino/1.0\n");  
          serial.print("user-agent: arduino/1.0\n");  
    client.print("connection: close\n");
          serial.print("connection: close\n");
    client.print("content-type: application/x-www-form-urlencoded\n");  
          serial.print("content-type: application/x-www-form-urlencoded\n");  
    client.print("content-length: ");
          serial.print("content-length: ");
    client.print(postdata.length());
          serial.print(postdata.length());
    client.print("\n\n");   // se necesitan dos line breaker para cerrar header
          serial.print("\n\n");
          
    // cuerpo del mensaje (http post body)
    client.print(postdata);
          serial.print(postdata);
    
    lastconnectiontime = millis();

    // chequeo sigo conectado -> post con exito
    if (client.connected())
    {
      serial.println();
      serial.println("----------------fin post-------------------------");
      serial.println();
      serial.println();
      failedcounter=0;
    } else {
      failedcounter++;
      serial.println("conexion con servidor perdida");
      serial.print("conexion perdida nº ");
      serial.println(string(failedcounter));
      serial.println();
    }
    
  }
  else  // no sido capaz de conectar con el servidor
  {
     failedcounter++;
     serial.println("no puedo conectarme servidor");
     serial.print("conexion perdida num. ");
     serial.println(string(failedcounter));
     serial.println();
     lastconnectiontime = millis();
  }
}

how memory have available? i'm guessing string usage killing memory. there no reason use strings. trying can done using strings, no dynamic memory allocation fragmenting memory.

http://playground.arduino.cc/code/availablememory

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