MQTT code error from arduino to RPi Nodered

#1

Hi.
I m using ADXL345 connected to Wemos D1 Mini and wish to send data via MQTT to RPi and Nodered.

The file attachment code works for DHT11 to Nodered but when i modify the codes for ADXL345 it has error.
The original ADXL345 code works on serial monitor on Arduino IDE.

Hope i can get some help on this

Thank you

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>

#include <ESP8266WiFi.h>
#include <PubSubClient.h>


// Change the credentials below, so your ESP8266 connects to your router
const char* ssid = "xxx";
const char* password = "xxxx";

// Change the variable to your Raspberry Pi IP address, so it connects to your MQTT broker
const char* mqtt_server = "xxxxx";

// Initializes the espClient. You should change the espClient name if you have multiple ESPs running in your home automation system
WiFiClient espClient;
PubSubClient client(espClient);



// Don't change the function below. This functions connects your ESP8266 to your router
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.print("WiFi connected - ESP IP address: ");
  Serial.println(WiFi.localIP());
}


// This functions is executed when some device publishes a message to a topic that your ESP8266 is subscribed to
// Change the function below to add logic to your program, so when a device publishes a message to a topic that 
// your ESP8266 is subscribed you can actually do something
void callback(String topic, byte* message, unsigned int length) {
  Serial.print("Message arrived on topic: ");
  Serial.print(topic);
  Serial.print(". Message: ");
  String messageTemp;
  
  for (int i = 0; i < length; i++) {
    Serial.print((char)message[i]);
    messageTemp += (char)message[i];
  }
  Serial.println();

}

// This functions reconnects your ESP8266 to your MQTT broker
// Change the function below if you want to subscribe to more topics with your ESP8266 
void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    /*
     YOU MIGHT NEED TO CHANGE THIS LINE, IF YOU'RE HAVING PROBLEMS WITH MQTT MULTIPLE CONNECTIONS
     To change the ESP device ID, you will have to give a new name to the ESP8266.
     Here's how it looks:
       if (client.connect("ESP8266Client")) {
     You can do it like this:
       if (client.connect("ESP1_Office")) {
     Then, for the other ESP:
       if (client.connect("ESP2_Garage")) {
      That should solve your MQTT multiple connections problem
    */
    if (client.connect("ESP8266Client")) {
      Serial.println("connected");  
      // Subscribe or resubscribe to a topic
      // You can subscribe to more topics (to control more LEDs in this example)
      client.subscribe("room/lamp");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}





/* Assign a unique ID to this sensor at the same time */
Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345);
 
void displaySensorDetails(void)
{
 sensor_t sensor;
 accel.getSensor(&sensor);
 Serial.println("------------------------------------");
 Serial.print ("Sensor: "); Serial.println(sensor.name);
 Serial.print ("Driver Ver: "); Serial.println(sensor.version);
 Serial.print ("Unique ID: "); Serial.println(sensor.sensor_id);
 Serial.print ("Max Value: "); Serial.print(sensor.max_value); Serial.println(" m/s^2");
 Serial.print ("Min Value: "); Serial.print(sensor.min_value); Serial.println(" m/s^2");
 Serial.print ("Resolution: "); Serial.print(sensor.resolution); Serial.println(" m/s^2"); 
 Serial.println("------------------------------------");
 Serial.println("");
 delay(500);
}
 
void displayDataRate(void)
{
 Serial.print ("Data Rate: "); 
 
 switch(accel.getDataRate())
 {
 case ADXL345_DATARATE_3200_HZ:
 Serial.print ("3200 "); 
 break;
 case ADXL345_DATARATE_1600_HZ:
 Serial.print ("1600 "); 
 break;
 case ADXL345_DATARATE_800_HZ:
 Serial.print ("800 "); 
 break;
 case ADXL345_DATARATE_400_HZ:
 Serial.print ("400 "); 
 break;
 case ADXL345_DATARATE_200_HZ:
 Serial.print ("200 "); 
 break;
 case ADXL345_DATARATE_100_HZ:
 Serial.print ("100 "); 
 break;
 case ADXL345_DATARATE_50_HZ:
 Serial.print ("50 "); 
 break;
 case ADXL345_DATARATE_25_HZ:
 Serial.print ("25 "); 
 break;
 case ADXL345_DATARATE_12_5_HZ:
 Serial.print ("12.5 "); 
 break;
 case ADXL345_DATARATE_6_25HZ:
 Serial.print ("6.25 "); 
 break;
 case ADXL345_DATARATE_3_13_HZ:
 Serial.print ("3.13 "); 
 break;
 case ADXL345_DATARATE_1_56_HZ:
 Serial.print ("1.56 "); 
 break;
 case ADXL345_DATARATE_0_78_HZ:
 Serial.print ("0.78 "); 
 break;
 case ADXL345_DATARATE_0_39_HZ:
 Serial.print ("0.39 "); 
 break;
 case ADXL345_DATARATE_0_20_HZ:
 Serial.print ("0.20 "); 
 break;
 case ADXL345_DATARATE_0_10_HZ:
 Serial.print ("0.10 "); 
 break;
 default:
 Serial.print ("???? "); 
 break;
 } 
 Serial.println(" Hz"); 
}
 
void displayRange(void)
{
 Serial.print ("Range: +/- "); 
 
 switch(accel.getRange())
 {
 case ADXL345_RANGE_16_G:
 Serial.print ("16 "); 
 break;
 case ADXL345_RANGE_8_G:
 Serial.print ("8 "); 
 break;
 case ADXL345_RANGE_4_G:
 Serial.print ("4 "); 
 break;
 case ADXL345_RANGE_2_G:
 Serial.print ("2 "); 
 break;
 default:
 Serial.print ("?? "); 
 break;
 } 
 Serial.println(" g"); 
}
 
void setup(void) 
{
 

Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
 
 //Serial.begin(9600);
 Serial.println("Accelerometer Test"); Serial.println("");
 
 /* Initialise the sensor */
 if(!accel.begin())
 {
 /* There was a problem detecting the ADXL345 ... check your connections */
 Serial.println("Ooops, no ADXL345 detected ... Check your wiring!");
 while(1);
 }
 
 /* Set the range to whatever is appropriate for your project */
 accel.setRange(ADXL345_RANGE_16_G);
 // displaySetRange(ADXL345_RANGE_8_G);
 // displaySetRange(ADXL345_RANGE_4_G);
 // displaySetRange(ADXL345_RANGE_2_G);
 
 /* Display some basic information on this sensor */
 displaySensorDetails();
 
 /* Display additional settings (outside the scope of sensor_t) */
 displayDataRate();
 displayRange();
 Serial.println("");
}
 
void loop(void) 
{

 if (!client.connected()) {
    reconnect();
  }
  if(!client.loop())
    client.connect("ESP8266Client");
    
 /* Get a new sensor event */ 
 sensors_event_t event; 
 accel.getEvent(&event);

// I need help here. 
  client.publish("sensor/adxl", event.acceleration.x);   
  
 
 /* Display the results (acceleration is measured in m/s^2) */
 Serial.print("X: "); Serial.print(event.acceleration.x); Serial.print(" ");
 Serial.print("Y: "); Serial.print(event.acceleration.y); Serial.print(" ");
 Serial.print("Z: "); Serial.print(event.acceleration.z); Serial.print(" ");
 //Serial.println("m/s^2 ");
 delay(500);
}
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#2

Soooo, your arduino code is not working and you are posting this on the Node-RED forum?

What is the error telling you?

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#3

I am connecting to nodered mqtt. I m sorry if its wrong to ask here.

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#4

tryadxl:247: error: no matching function for call to 'PubSubClient::publish(const char [12], float&)'

client.publish("sensor/adxl", event.acceleration.x);

this is the error i think i need to change it to string maybe.

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#5

What does the Arduino variable return on event.acceleration ?? Is it a string, integer, float ? etc ?

Craig

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#6

Here is a snippet of my Arduino code for pushing values out to an MQTT stream

void PublishValues(){
  
    String temp_str;
    char temp[5];

   
    temp_str = String(AvgTankTemp); //converting ftemp (the float variable above) to a string 
    temp_str.toCharArray(temp, temp_str.length() + 1); //packaging up the data to publish to mqtt whoa...

    Serial.print("Publish message to MQTT on Topic/Temperature: ");//all of these Serial prints are to help with debugging
    Serial.println(temp);  
    
    MQTT.publish("TankTemperature", temp); //money shot

    temp_str = String(AvgRoofTemp); //converting ftemp (the float variable above) to a string 
    temp_str.toCharArray(temp, temp_str.length() + 1); //packaging up the data to publish to mqtt whoa...
    

So you can see yes you have to convert your values to be a string and then when they get to the other end - reconstruct them

Craig

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#7

Hi @mshaz

this is a Node-RED forum, and this is not really a question about using Node-RED, rather help for debugging some other code entirely that you happen to want to use in a system that also involves Node-RED. So it is right at the limit of what we'd consider on-topic for this forum.

Now, I'm obviously slightly conflicted, because the question you ask is related to my other open source project - the arduino PubSubClient library.

As I think you've identified, the second argument to client.publish must be a String - so you'll need to convert the float value held in event.acceleration.x to a string.

How you go about doing that is a topic for an arduino forum - there are plenty of guides for doing that out there.

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#8

I knew you were not going to be able to sit back and not comment on that Unbelievably good and ubiquitous MQTT library !!

Just out of interest - why does everything have to be sent as a string ? i..e was there some design constraint ?

Craig

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#9

It doesn't - it can be either a String (const char[]) or byte array (byte[]) if an additional length parameter is provided - see https://pubsubclient.knolleary.net/api.html for the list of available publish functions.

There was an feature request to provide convenience functions to publish various data types - so we'd automatically string encode them. But it never happened.

PubSubClient doesn't get much of a look-in with my time these days. I'm not actively doing anything on Arduino/ESP type devices. There's a huge backlog of pull-requests - some worth considering, some not. At some point soon, I really should tidy it up and do a new release.

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#10

When they make each day 26 hours long i am sure you will get on top of everything !!

Craig

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