I have cobbled together, from the library examples, a program to log temperature and humidity to an MQTT server. The SSID/password, MQTT server and port, and the MQTT publish path can all be set at run time. Once they are set, the device will remember and re-use the settings next time it boots.
I am using the Arduino IDE to program an ESP8266-01. It, in turn, talks to a DHT11 sensor for temperature and humidity data.
The program is found at https://github.com/PabluskiNC/TempHumidityLogger
#include <FS.h> //this needs to be first, or it all crashes and burns...
#include "DHT.h"
#define DHTPIN 2
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);
#include <ESP8266WiFi.h> //https://github.com/esp8266/Arduino
//needed for library
#include <DNSServer.h>
#include <ESP8266WebServer.h>
#include <WiFiManager.h> //https://github.com/tzapu/WiFiManager
#include <ArduinoJson.h> //https://github.com/bblanchon/ArduinoJson
#include <PubSubClient.h>
WiFiClient espClient;
PubSubClient client(espClient);
long mqtt_lastMsg = 0;
char mqtt_msg[50];
int mqtt_value = 0;
//define your default values here, if there are different values in config.json, they are overwritten.
char mqtt_server[40];
char mqtt_port[6] = "1883";
char mqtt_topic[34] = "OutTopic";
//flag for saving data
bool shouldSaveConfig = false;
//callback notifying us of the need to save config
void saveConfigCallback () {
Serial.println("Should save config");
shouldSaveConfig = true;
}
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
Serial.println();
//clean FS, for testing
//SPIFFS.format();
//read configuration from FS json
Serial.println("mounting FS...");
if (SPIFFS.begin()) {
Serial.println("mounted file system");
if (SPIFFS.exists("/config.json")) {
//file exists, reading and loading
Serial.println("reading config file");
File configFile = SPIFFS.open("/config.json", "r");
if (configFile) {
Serial.println("opened config file");
size_t size = configFile.size();
// Allocate a buffer to store contents of the file.
std::unique_ptr<char[]> buf(new char[size]);
configFile.readBytes(buf.get(), size);
DynamicJsonBuffer jsonBuffer;
JsonObject& json = jsonBuffer.parseObject(buf.get());
json.printTo(Serial);
if (json.success()) {
Serial.println("\nparsed json");
strcpy(mqtt_server, json["mqtt_server"]);
strcpy(mqtt_port, json["mqtt_port"]);
strcpy(mqtt_topic, json["mqtt_topic"]);
} else {
Serial.println("failed to load json config");
}
}
}
} else {
Serial.println("failed to mount FS");
}
//end read
// The extra parameters to be configured (can be either global or just in the setup)
// After connecting, parameter.getValue() will get you the configured value
// id/name placeholder/prompt default length
WiFiManagerParameter custom_mqtt_server("server", "mqtt server", mqtt_server, 40);
WiFiManagerParameter custom_mqtt_port("port", "mqtt port", mqtt_port, 5);
WiFiManagerParameter custom_mqtt_topic("topic", "mqtt topic", mqtt_topic, 32);
//WiFiManager
//Local intialization. Once its business is done, there is no need to keep it around
WiFiManager wifiManager;
//set config save notify callback
wifiManager.setSaveConfigCallback(saveConfigCallback);
//set static ip
//wifiManager.setSTAStaticIPConfig(IPAddress(10, 0, 1, 99), IPAddress(10, 0, 1, 1), IPAddress(255, 255, 255, 0));
//add all your parameters here
wifiManager.addParameter(&custom_mqtt_server);
wifiManager.addParameter(&custom_mqtt_port);
wifiManager.addParameter(&custom_mqtt_topic);
//reset settings - for testing
//wifiManager.resetSettings();
//set minimu quality of signal so it ignores AP's under that quality
//defaults to 8%
//wifiManager.setMinimumSignalQuality();
//sets timeout until configuration portal gets turned off
//useful to make it all retry or go to sleep
//in seconds
//wifiManager.setTimeout(120);
//fetches ssid and pass and tries to connect
//if it does not connect it starts an access point with the specified name
//here "AutoConnectAP"
//and goes into a blocking loop awaiting configuration
if (!wifiManager.autoConnect("AutoConnectAP", "password")) {
Serial.println("failed to connect and hit timeout");
delay(3000);
//reset and try again, or maybe put it to deep sleep
ESP.reset();
delay(5000);
}
//if you get here you have connected to the WiFi
Serial.println("connected...yeey :)");
//read updated parameters
strcpy(mqtt_server, custom_mqtt_server.getValue());
strcpy(mqtt_port, custom_mqtt_port.getValue());
strcpy(mqtt_topic, custom_mqtt_topic.getValue());
//save the custom parameters to FS
if (shouldSaveConfig) {
Serial.println("saving config");
DynamicJsonBuffer jsonBuffer;
JsonObject& json = jsonBuffer.createObject();
json["mqtt_server"] = mqtt_server;
json["mqtt_port"] = mqtt_port;
json["mqtt_topic"] = mqtt_topic;
File configFile = SPIFFS.open("/config.json", "w");
if (!configFile) {
Serial.println("failed to open config file for writing");
}
json.printTo(Serial);
json.printTo(configFile);
configFile.close();
//end save
}
client.setServer(mqtt_server, stringToNumber(mqtt_port));
client.setCallback(callback);
Serial.println("local ip");
Serial.println(WiFi.localIP());
dht.begin();
}
int stringToNumber(String thisString) {
int i, value, length;
length = thisString.length();
char blah[(length + 1)];
for (i = 0; i < length; i++) {
blah[i] = thisString.charAt(i);
}
blah[i] = 0;
value = atoi(blah);
return value;
}
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();
// Switch on the LED if an 1 was received as first character
if ((char)payload[0] == '1') {
digitalWrite(BUILTIN_LED, LOW); // Turn the LED on (Note that LOW is the voltage level
// but actually the LED is on; this is because
// it is acive low on the ESP-01)
} else {
digitalWrite(BUILTIN_LED, HIGH); // Turn the LED off by making the voltage HIGH
}
}
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
Serial.print(mqtt_server);
Serial.print(":");
Serial.print(mqtt_port);
Serial.print("...");
// Attempt to connect
if (client.connect("ESP8266Client")) {
Serial.println("connected");
// Once connected, publish an announcement...
client.publish(mqtt_topic, "Reconnected");
// ... and resubscribe
//client.subscribe("inTopic");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}
void loop() {
// put your main code here, to run repeatedly:
float h = dht.readHumidity();
float t = dht.readTemperature();
if (isnan(t) || isnan(h)) {
Serial.println("Failed to read from DHT");
} else {
Serial.print("Temp:");
Serial.print(t);
Serial.print( "*C Humidity:");
Serial.print(h);
Serial.println("%");
if (!client.connected()) {
reconnect();
}
client.loop();
//long now = millis();
//if (now - mqtt_lastMsg > 2000) {
// lastMsg = now;
// ++mqtt_value;
char temp[7];
dtostrf(t,4,2,temp); //convert float to char
snprintf (mqtt_msg, 50, "%s C", temp);
// Serial.print("Publish message: ");
// Serial.println(msg);
// client.publish(mqtt_topic, msg);
//}
char pub_topic[34];
strcpy(pub_topic,mqtt_topic);
strcat(pub_topic,"/temperature");
client.publish( pub_topic , mqtt_msg);
Serial.print("Publish: ");
Serial.print(pub_topic);
Serial.print(" , ");
Serial.println(mqtt_msg);
dtostrf(h,4,2,temp); //convert float to char
snprintf (mqtt_msg, 50, "%s %", temp);
strcpy(pub_topic,mqtt_topic);
strcat(pub_topic,"/humidity");
client.publish(pub_topic,mqtt_msg);
Serial.print("Publish: ");
Serial.print(pub_topic);
Serial.print(" , ");
Serial.println(mqtt_msg);
}
delay(5000);
}