Yesterday I took my RGB LED strip project and upgraded it to use MQTT instead of the simple terminal server I was using before. I couldn’t get it working using my WiFly shield, the system would work fine for five minutes or so and then crash. I did a little digging around, thinking it may be a memory issue, put came up blank. So ditch the WiFly shield and dig out an Ethernet shield…
Arduino Ethernet RGB Lights
Then installed the Nick O’Leary’s Arduino MQTT library, and got coding:
/*
* Ethernet RGB LEDS with MQTT
* (c) Mark McKillen
*
*/
#include <SPI.h>
#include <Ethernet.h>
#include <PubSubClient.h>
#define MQTT_SERVER "<Mosquitto Server IP>"
byte MAC_ADDRESS[] = { 0x91, 0xA3, 0xAA, 0x00, 0x01, 0x03 };
char message_buff[30];
int redPin = 3; // Red LED, connected to digital pin 9
int greenPin = 5; // Green LED, connected to digital pin 10
int bluePin = 6; // Blue LED, connected to digital pin 11
EthernetClient ethClient; // Ethernet object
PubSubClient client( MQTT_SERVER, 1883, callback, ethClient); // MQTT object
void setup() {
Serial.begin(9600);
Serial.println("Net begin");
if (Ethernet.begin(MAC_ADDRESS) == 0) // Get connected!
{
Serial.println("Failed to configure Ethernet using DHCP");
return;
}
Serial.print("IP: "); // A little debug.. show IP address
Serial.println(Ethernet.localIP());
if (client.connect("arduinoClient")) { // connect to MQTT server
client.subscribe("rgblight"); // subscribe to topic "rgblight"
Serial.println("Connected to MQTT"); // let us know this has happened
}
}
void loop()
{
client.loop(); // loop for ever waiting for MQTT event
}
// handles message arrived on subscribed topic
void callback(char* topic, byte* payload, unsigned int length) {
int i = 0;
// create character buffer with ending null terminator (string)
for(i=0; i<length; i++) {
message_buff[i] = payload[i];
}
message_buff[i] = '\0';
long colorVal = strtol( message_buff, NULL, 16);
analogWrite(redPin, (colorVal&0xff0000)>>16 );
analogWrite(greenPin, (colorVal&0x00ff00)>>8 );
analogWrite(bluePin, (colorVal&0x0000ff)>>0 );
}
Really simple, that is the cool thing about MQTT, it’s so easy and powerful.
To light the lights all I need to do is:
mosquitto_pub -h <mqtt server> -t rgblight -m "ff0000" # All red
mosquitto_pub -h <mqtt server> -t rgblight -m "00ff00" # All green
mosquitto_pub -h <mqtt server> -t rgblight -m "0000ff" # All blue
The lights respond quickly, much faster than my last version. Success!
After I install the i2c tools, I was able to drive the relays and monitor the inputs no problem.
