Hi,
I recently moved a code from a nano to an ESP8266 and Im getting an error when I combine a String with a char[], which on the nano worked fine. Im thinking it must be due to a String object that is in a library that the nano loads automatically whereas the ESP8266 doesnt have it.
What is the best solution? Should I load an extra library onto the ESP8266 or should I parse this differently?
#include <ESP8266WiFi.h>
#include "DHT.h"
#define DHTPIN 2 // what pin we're connected to
#define DHTTYPE DHT22 // DHT 22 (AM2302)
DHT dht(DHTPIN, DHTTYPE);
const char* ssid = "myssid";
const char* password = "mypwd";
const char* host = "myserver.com";
unsigned long previousMillis = 0; // will store last time was updated
const long interval = 180000;
char tempString[20];
char humString[20];
void setup() {
Serial.begin(115200);
delay(100);
// We start by connecting to a WiFi network
Serial.println();
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
}
int value = 0;
void start_test () {
//For DHT22 Grove Pro
float h = dht.readHumidity();
float t = dht.readTemperature();
dtostrf(t, 4, 2, tempString); //convert flat to char
dtostrf(h, 4, 2, humString); //convert flat to char
}
void loop() {
///////////INSERTED millis-sample code
unsigned long currentMillis = millis();
if (currentMillis - previousMillis <= interval) { //when time elapsed is LESS than interval of 30 mins
} else { //if deltaTimeElapsed is GREATER than target interval, sample and post...
previousMillis = currentMillis; //sets previous-0 to current-3600
start_test(); //sample
}
delay(5000);
++value;
Serial.print("connecting to ");
Serial.println(host);
// Use WiFiClient class to create TCP connections
WiFiClient client;
const int httpPort = 80;
if (!client.connect(host, httpPort)) {
Serial.println("connection failed");
return;
}
// We now create a URI for the request
String url = "/emoncms/input/post.json?apikey=mykey&node=fortnite&json={\"t\":" + tempString + ",\"h\":" + humString + "}";
Serial.print("Requesting URL: ");
Serial.println(url);
client.print(String("GET ") + url + " HTTP/1.1\r\n" +
"Host: " + host + "\r\n" +
"Connection: close\r\n\r\n");
delay(500);
while(client.available()){
String line = client.readStringUntil('\r');
Serial.print(line);
}
Serial.println();
Serial.println("closing connection");
}
Error:
exit status 1
invalid operands of types 'const char [90]' and 'char [20]' to binary 'operator+'