TWIL 0007 | 24w44 | Arduino - ESP
Arduino Uno with ESP8266
I bought a board that is two boards in one place. Of course I didn’t know that beforehand - the price for learning everything on the fly. I found some firmware for ESP, that should do everything out of box so I need to care only about Uno. But never got that working.
What I need is to connect to MQTT (Mosquitto) and pub/sub messages from that. Turned out the chips communicate between each other through serial and that can be used for passing messages. Life-saving tutorial on how to make it work.
Code is hacky, but working.
My ESP code:
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
// Update these with values suitable for your network.
// TODO to config file
const char* ssid = "";
const char* password = "";
const char* mqtt_server = "192.168.x.y";
const int mqtt_port = 1883;
const char* log_queue = "log";
WiFiClient espClient;
PubSubClient client(espClient);
unsigned long lastMsg = 0;
#define MSG_BUFFER_SIZE (15)
char msg[MSG_BUFFER_SIZE];
String msg_s = "";
int value = 0;
void setup_wifi() {
delay(10);
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
}
}
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
// Create a random client ID
String clientId = "ESP8266Client-";
clientId += String(random(0xffff), HEX);
// Attempt to connect
if (client.connect(clientId.c_str())) {
// Once connected, publish an announcement...
client.publish(log_queue, "connected");
// ... and resubscribe
client.subscribe("queue");
} else {
// Wait 5 seconds before retrying
delay(500);
}
}
}
void callback(char* topic, byte* payload, unsigned int length) {
/**
* callback function takes a msg from MQTT, prepends "ESP|" and pass it into Serial
*/
msg_s = "";
for (int i = 0; i < length; i++) {
msg_s.concat((char)payload[i]);
}
Serial.println("ESP|" + msg_s);
}
void setup() {
Serial.begin(115200);
setup_wifi();
client.setServer(mqtt_server, mqtt_port);
client.setCallback(callback);
}
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
/**
* Here we transfer msgs from Uno to Log queue
*/
if (Serial.available()) {
String serialMsg = Serial.readString();
if (serialMsg.startsWith("UNO|")) {
// here you can also trim "UNO|" if you need to
serialMsg.toCharArray(msg, MSG_BUFFER_SIZE);
client.publish(log_queue, msg);
}
}
delay(5); // to keep it sane
}
So the messages from the MQTT are prepended with “ESP|” and printed to the Serial. Messages from the Uno have “UNO|” prepended and those are routed to the log_queue.
Uno code:
#include <Arduino.h>
String msg;
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
Serial.flush();
}
void loop() {
// put your main code here, to run repeatedly:
if (Serial.available()) {
msg = Serial.readString();
if (msg.startsWith("ESP|")) {
// DO MAGIC HERE
// SEND MESSAGE TO QUEUE
Serial.println("UNO|MESSAGE");
}
}
delay(20); // to keep it sane
}
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Everything is a nail
