A newbie in Arduino- and I'm trying to concatenate string and chars ( well in python it is quite different ).
I'm trying to post a MQTT message- constructed following format to the client.publish(outTopic, "["+outTopic+"]"+ msg)
while outTopic
is a char* variable, and msg
is char- but I get an error for such concatenation.
please your help
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
// GPIOs on SONOFF board
int LED_SONOFF = 13;
int REL_SONOFF = 12;
int PIN_SW = 14;
const char* ssid = "HomeNetwork_2.4G";
const char* password = "pswd";
const char* mqtt_server = "192.168.2.113";
WiFiClient espClient;
PubSubClient client(espClient);
char msg[50];
const char* outTopic = "HomePi/Dvir/Messages";
const char* inTopic = "HomePi/Dvir/Windows/SONOFF";
const char* inTopic2 = "HomePi/Dvir/Windows/All";
const char* clientID = "Sonoff#1";
String m1, m2;
void start_wifi() {
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
Serial.print("IP address: ");
Serial.println(WiFi.localIP());
}
void setup() {
start_wifi(); // start wifi service
Serial.begin(115200); // start serial service
delay(10);
// define sonoff gpios
pinMode(LED_SONOFF, OUTPUT);
pinMode(REL_SONOFF, OUTPUT);
pinMode(PIN_SW, INPUT_PULLUP); // GPIO14 has a pullup resistor
digitalWrite(LED_SONOFF,HIGH); // LED high is OFF
digitalWrite(REL_SONOFF,LOW);
// start mqtt
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
}
void switch_on() {
digitalWrite(REL_SONOFF,HIGH);
digitalWrite(LED_SONOFF, LOW); // LED ON
pub_mqtt("Switch ON");
}
void switch_off() {
digitalWrite(REL_SONOFF,LOW);
digitalWrite(LED_SONOFF, HIGH); // LED OFF
pub_mqtt("Switch OFF");
}
void callback(char* topic, byte* payload, unsigned int length) {
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i < length; i++) {
Serial.print((char)payload[i]);
}
Serial.println();
if ((char)payload[0] == '1') {
switch_on();
}
if ((char)payload[0] == '0') {
switch_off();
Serial.print("payload: ");
Serial.println(payload[0]);
}
}
void reconnect() {
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
if (client.connect("ESP8266Client")) {
Serial.println("connected");
client.publish(outTopic, "Connected");
client.subscribe(inTopic);
m1="Subscribed to: "+inTopic;
client.publish(outTopic, m1);
if (inTopic2 !=""){
client.subscribe(inTopic2);
m2="Subscribed to: ";//+ String(inTopic2);
client.publish(outTopic, m2);
}
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
delay(5000);
}
}
}
void pub_mqtt(char* msg) {
client.publish(outTopic, msg);
}
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
if (digitalRead(PIN_SW)==1) {
if (digitalRead(REL_SONOFF)!=LOW) {
switch_off();
}
}
else if (digitalRead(PIN_SW)==0) {
if (digitalRead(REL_SONOFF)!=HIGH){
switch_on();
}
}
delay(100);
}