Hey guys I had a question; i am trying to get my OLED screen to print any MQTT message I sent to a specific topic. I've manage to cannibalize some code together and get everything working besides getting the OLED to print my MQTT message.
I have verified the OLED works, I can connect to the MQTT server, I can subscribe and publish messages.
Basically I am trying to get the OLED to display the MQTT subscribed message, but I am having no luck.
I would really appreciate any ones help. Thank you in advance!
I am getting the following error;
In file included from C:\Users\Scott Ramirez\Desktop\sketch_mar30a\sketch_mar30a.ino:2:0:
C:\Program Files (x86)\Arduino\libraries\OLED/OLED.h:32:8: error: initializing argument 1 of 'void OLED::print(char*, uint8_t, uint8_t)' [-fpermissive]
void print(char *s, uint8_t r=0, uint8_t c=0);
^
exit status 1
invalid conversion from 'char' to 'char*' [-fpermissive]
Here is the specific snippet of code Thats giving me issues; LINE 7
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]);
display.print(payload, 0, 5);
}
Complete Sketch, Board: ESP8266
/*
Basic ESP8266 MQTT example
This sketch demonstrates the capabilities of the pubsub library in combination
with the ESP8266 board/library.
It connects to an MQTT server then:
- publishes "hello world" to the topic "outTopic" every two seconds
- subscribes to the topic "inTopic", printing out any messages
it receives. NB - it assumes the received payloads are strings not binary
- If the first character of the topic "inTopic" is an 1, switch ON the ESP Led,
else switch it off
It will reconnect to the server if the connection is lost using a blocking
reconnect function. See the 'mqtt_reconnect_nonblocking' example for how to
achieve the same result without blocking the main loop.
To install the ESP8266 board, (using Arduino 1.6.4+):
- Add the following 3rd party board manager under "File -> Preferences -> Additional Boards Manager URLs":
http://arduino.esp8266.com/stable/package_esp8266com_index.json
- Open the "Tools -> Board -> Board Manager" and click install for the ESP8266"
- Select your ESP8266 in "Tools -> Board"
*/
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
#include "OLED.h"
OLED display(4, 5);
// Update these with values suitable for your network.
const char* ssid = "Scott's iPhone";
const char* password = "scott123";
const char* mqtt_server = "192.168.1.88";
WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;
void setup() {
display.begin();
display.print("PSI:", 0, 1);
delay(3*1000);
pinMode(BUILTIN_LED, OUTPUT); // Initialize the BUILTIN_LED pin as an output
Serial.begin(115200);
setup_wifi();
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
}
void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
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());
}
void callback(char* topic, byte* payload, unsigned int length) {
//display.print("test", 0, 5);
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i < length; i++) {
//Serial.print((char)payload[i]);
display.print(payload, 0, 5);
}
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...");
// Attempt to connect
if (client.connect("ESP8266Client")) {
Serial.println("connected");
// Once connected, publish an announcement...
client.publish("outTopic", "hello world");
// ... 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() {
if (!client.connected()) {
reconnect();
}
client.loop();
long now = millis();
if (now - lastMsg > 2000) {
lastMsg = now;
++value;
snprintf (msg, 75, "hello world #%ld", value);
Serial.print("Publish message: ");
Serial.println(msg);
client.publish("outTopic", msg);
//display.print(msg, 0, 5);
}
}