MQTT subscribe question

Projects Programming
1

Hello everyone, I'm learning so please be gentle. I'm really in the ''cut and paste'' part of my learning journey.
I've managed to put the code together but now i want to subscribe to a MQTT topic but I just can't work it out!!
I'd like to receive a reading from an temp sensor (via mqtt) and display in on the graph / logger as well as the locally logged temperature data.
And code help would be appreciated.

#include <Wire.h>
#include <SPI.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <ESP8266WiFi.h>
#include <Ticker.h>
#include <AsyncMqttClient.h>
#include <PubSubClient.h>
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"
#include <Fonts/FreeSerif9pt7b.h> // set font - must be included above at top. https://learn.adafruit.com/adafruit-gfx-graphics-library/using-fonts
#include <Fonts/FreeSans9pt7b.h>
#include <NTPClient.h>
#include <WiFiUdp.h>


//----------------------------------------------------------------------------------------------------
// For the Adafruit shield, these are the default.
#define TFT_DC D4
#define TFT_CS D8
#define WIFI_SSID "*****"
#define WIFI_PASSWORD "*********"

// Raspberri Pi Mosquitto MQTT Broker
#define MQTT_HOST IPAddress(192, 168, 1, 118)
// For a cloud MQTT broker, type the domain name
//#define MQTT_HOST "example.com"
#define MQTT_PORT 1883

// Temperature MQTT Topics
#define MQTT_PUB_TEMP "esp/ds18b20/temperature"


//https://en.wikipedia.org/wiki/List_of_UTC_time_offsets
// offset for Sydney is + 10 or 11 hours dependant of daylight saving.
// offset is seconds calculated as follows: +10hours = 10x60x60=36000 11x60x60=39600
const long utcOffsetInSeconds = 3600;

char daysOfTheWeek[7][12] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

// Define NTP Client to get time
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, "pool.ntp.org", utcOffsetInSeconds);


// GPIO where the DS18B20 is connected to
const int oneWireBus = 5; //(GPIO5 - D1)

OneWire oneWire(oneWireBus);
DallasTemperature sensors(&oneWire);

float temp;
float xscale;
float del;
//float temp_readings;
//float temperature;
// Use hardware SPI (on Uno use #13, #12, #11) and the above for CS/DC
Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC);

float min_temp = 100, max_temp = -100;

#define max_readings 290

#define del 599250 // 599250 for 48 hours -measurement rate in ms - take off 750ms for the time needed to update temp readings.

float history6;
float history12;
float history18;
float history24;
float history30;
float history36;
float history42;
float history48;
float historyA;
float historyB;
float historyC;
float historyD;
float historyE;
float historyF;
float historyG;
float historyH;
float temp_error_offset;

float temp_readings[max_readings+1] = {0};
int   reading = 290; //  starting point of graph

#define temp_error_offset   0  // calibration factor?

#define autoscale_on  true
#define autoscale_off false
#define barchart_on   true
#define barchart_off  false

// Assign names to common 16-bit color values:
#define BLACK       0x0000
#define BLUE        0x001F
#define RED         0xF800
#define GREEN       0x07E0
#define CYAN        0x07FF
#define YELLOW      0xFFE0
#define WHITE       0xFFFF
#define MAGENTA     0xF81F
#define GREY        0x4228
//----------------------------------------------------------------------------------------------------
 /* (C) D L BIRD
 *  This function will draw a graph on a TFT / LCD display, it requires an array that contrains the data to be graphed.
 *  The variable 'max_readings' determines the maximum number of data elements for each array. Call it with the following parametric data:
 *  x_pos - the x axis top-left position of the graph
 *  y_pos - the y-axis top-left position of the graph, e.g. 100, 200 would draw the graph 100 pixels along and 200 pixels down from the top-left of the screen
 *  width - the width of the graph in pixels
 *  height - height of the graph in pixels
 *  Y1_Max - sets the scale of plotted data, for example 5000 would scale all data to a Y-axis of 5000 maximum
 *  data_array1 is parsed by value, externally they can be called anything else, e.g. within the routine it is called data_array1, but externally could be temperature_readings
 *  auto_scale - a logical value (TRUE or FALSE) that switches the Y-axis autoscale On or Off
 *  barchart_on - a logical value (TRUE or FALSE) that switches the drawing mode between barhcart and line graph
 *  barchart_colour - a sets the title and graph plotting colour
 *  If called with Y!_Max value of 500 and the data never goes above 500, then autoscale will retain a 0-500 Y scale, if on, it will increase the scale to match the data to be displayed, and reduce it accordingly if required.
 *  auto_scale_major_tick, set to 1000 and autoscale with increment the scale in 1000 steps.
 */


 
 void DrawGraph(int x_pos, int y_pos, int width, int height, int Y1Max, String title, float DataArray[max_readings], boolean auto_scale, boolean barchart_mode, int graph_colour) {
  #define auto_scale_major_tick 5 // Sets the autoscale increment, so axis steps up in units of e.g. 5
  #define yticks 15                // 5 y-axis division markers
  int maxYscale = 0;
  if (auto_scale) {
    for (int i=1; i <= max_readings; i++ ) if (maxYscale <= DataArray[i]) maxYscale = DataArray[i];
    maxYscale = ((maxYscale + auto_scale_major_tick + 2) / auto_scale_major_tick) * auto_scale_major_tick; // Auto scale the graph and round to the nearest value defined, default was Y1Max
    if (maxYscale < Y1Max) Y1Max = maxYscale; 
  }
  //Graph the received data contained in an array
  // Draw the graph outline
  tft.drawRect(x_pos,y_pos,width+2,height+3,WHITE);
  tft.setTextSize(2);
  tft.setTextColor(graph_colour);
  tft.setCursor(x_pos + (width - title.length()*12)/2,y_pos-20); // 12 pixels per char assumed at size 2 (10+2 pixels)
  tft.print(title);
  tft.setTextSize(1);
  // Draw the data
  int x1,y1,x2,y2;
  for(int gx = 1; gx <= max_readings; gx++){
    x1 = x_pos + gx * width/max_readings; 
    y1 = y_pos + height;
    x2 = x_pos + gx * width/max_readings; // max_readings is the global variable that sets the maximum data that can be plotted 
    y2 = y_pos + height - constrain(DataArray[gx],0,Y1Max) * height / Y1Max + 1;
    if (barchart_mode) {
      tft.drawLine(x1,y1,x2,y2,graph_colour);
    } else {
      tft.drawPixel(x2,y2,graph_colour);
      tft.drawPixel(x2,y2-1,graph_colour); // Make the line a double pixel height to emphasise it, -1 makes the graph data go up!
      
    }
  }
  //Draw the Y-axis scale
  for (int spacing = 0; spacing <= yticks; spacing++) {
    #define number_of_dashes 80
    for (int j=0; j < number_of_dashes; j++){ // Draw dashed graph grid lines
      if (spacing < yticks) tft.drawFastHLine((x_pos+1+j*width/number_of_dashes),y_pos+(height*spacing/yticks),width/(2*number_of_dashes),GREY);
    }

    tft.setFont(); 
    tft.setTextSize(1);
    tft.setTextColor(YELLOW);
    tft.setCursor((x_pos-20),y_pos+height*spacing/yticks-4);
    tft.print(Y1Max - Y1Max / yticks * spacing);
    tft.setFont(); 
    
  }

  tft.drawRect(x_pos,y_pos,width+2,height+3,WHITE);
  tft.setTextSize(2);
  tft.setTextColor(graph_colour);
  tft.setCursor(x_pos + (width - title.length()*12)/2,y_pos-20); // 12 pixels per char assumed at size 2 (10+2 pixels)
  tft.print(title);
  tft.setTextSize(1);




}

AsyncMqttClient mqttClient;
Ticker mqttReconnectTimer;

WiFiEventHandler wifiConnectHandler;
WiFiEventHandler wifiDisconnectHandler;
Ticker wifiReconnectTimer;

unsigned long previousMillis = 0;   // Stores last time temperature was published
const long interval = 10000;        // Interval at which to publish sensor readings

void connectToWifi() {
  Serial.println("Connecting to Wi-Fi...");
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
 
}

void onWifiConnect(const WiFiEventStationModeGotIP& event) {
  Serial.println("Connected to Wi-Fi.");
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:Fail");
  tft.setTextColor(GREEN);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:OK");
  connectToMqtt();
}

void onWifiDisconnect(const WiFiEventStationModeDisconnected& event) {
  Serial.println("Disconnected from Wi-Fi.");
  mqttReconnectTimer.detach(); // ensure we don't reconnect to MQTT while reconnecting to Wi-Fi
  wifiReconnectTimer.once(2, connectToWifi);
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:OK");
  tft.setTextColor(RED);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:Fail");
 
  
}

void connectToMqtt() {
  Serial.println("Connecting to MQTT...");
  mqttClient.connect();
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(0,233);
  tft.print("Remote Database: Disconnected (Try: Restart PI)");
  tft.setTextColor(YELLOW);
  tft.setTextSize(1);
  tft.setCursor(0,233);
  tft.print("Remote Database: Connecting.....");
 
}

void onMqttConnect(bool sessionPresent) {
  Serial.println("Connected to MQTT.");
  Serial.print("Session present: ");
  Serial.println(sessionPresent);
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(0,233);
  tft.print("Remote Database: Connecting.....");
  tft.setTextColor(GREEN);
  tft.setTextSize(1);
  tft.setCursor(0,233);
  tft.print("Remote Database: Conneted");
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(270,0);
  tft.print("DB:FAIL");
  tft.setTextColor(GREEN);
  tft.setTextSize(1);
  tft.setCursor(265,0);
  tft.print("DB  :OK");

 
}

void onMqttDisconnect(AsyncMqttClientDisconnectReason reason) {
  Serial.println("Disconnected from MQTT.");
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(0,233);
  tft.print("Remote Database: Connecting.....");
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(0,233);
  tft.print("Remote Database: Connected");
  tft.setTextColor(RED);
  tft.setTextSize(1);
  tft.setCursor(0,233);
  tft.print("Remote Database: Disconnected (Try: Restart PI)");
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(265,0);
  tft.print("DB  :OK");
  tft.setTextColor(RED);
  tft.setTextSize(1);
  tft.setCursor(270,0);
  tft.print("DB:FAIL");
  

  if (WiFi.isConnected()) {
    mqttReconnectTimer.once(2, connectToMqtt);

  }
}

void onMqttPublish(uint16_t packetId) {
  Serial.print("Publish acknowledged.");
  Serial.print("  packetId: ");
  Serial.println(packetId);
  tft.setTextColor(GREEN);
  tft.setTextSize(1);
  tft.setCursor(265,0);
  tft.print("DB  :OK");
  //tft.print(packetId);
}

void setup(){

 timeClient.begin();

  
  Serial.begin(9600);

  wifiConnectHandler = WiFi.onStationModeGotIP(onWifiConnect);
  wifiDisconnectHandler = WiFi.onStationModeDisconnected(onWifiDisconnect);

  mqttClient.onConnect(onMqttConnect);
  mqttClient.onDisconnect(onMqttDisconnect);
  //mqttClient.onSubscribe(onMqttSubscribe);
  //mqttClient.onUnsubscribe(onMqttUnsubscribe);
  mqttClient.onPublish(onMqttPublish);
  mqttClient.setServer(MQTT_HOST, MQTT_PORT);
  // If your broker requires authentication (username and password), set them below
  //mqttClient.setCredentials("REPlACE_WITH_YOUR_USER", "REPLACE_WITH_YOUR_PASSWORD");
  
  connectToWifi();
  

  
  tft.begin(); // Start the TFT display
  tft.setRotation(3);
  tft.setTextSize(2);
  tft.setTextColor(BLACK);
  tft.fillScreen(BLACK);   // Clear the screen

  sensors.begin();
  sensors.requestTemperatures(); 
  delay(1000);
  temp = sensors.getTempCByIndex(0)+ temp_error_offset;


  
  analogWriteFreq(500);    // Enable TFT display brightness
  analogWrite(D0, 750);    // Set display brightness using D0 as driver pin, connects to TFT Backlight pin

  for (int x = 0; x <= max_readings; x++){
    temp_readings[x] = 0;
    
  } // Clears the arrays
  // Preset the max and min values of temperature and humidity

 tft.setFont();//reset font
  
xscale = (290 * ((((del+750) / 1000))/60)/60);

timeClient.update();

delay(2000);

}



void loop(){

Serial.begin(9600);
timeClient.update();

if ((timeClient.getHours() >=18) && (timeClient.getHours() <=6)) { analogWrite(D0,050);}  // time for screen to go off and onn
else { analogWrite(D0,750);}

xscale = (290 * ((((del+750) / 1000))/60)/60);

tft.fillScreen(BLACK);

  tft.setFont();             //reset font
  tft.setTextColor(YELLOW);
  tft.setTextSize(1);
  
 // tft.setCursor(15,205);
 // tft.drawLine(20,202,20,204,BLACK);
 // tft.setTextSize(1);
//  tft.print(xscale,0); // if using a smaller scale chnage out the 0 for a 1 to give decimal points



//-48 hours
  tft.setCursor(6,205);
  history24 = (timeClient.getHours()-24);
  history48 = (timeClient.getHours()-48);
  if (history48 <0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history48 < -24) {tft.setTextColor(CYAN);}
  if (history24 <0){historyD = history24 + 24;}
  if (history24 <0){
    if (historyD<10) {tft.print("0");}
    tft.print(historyD,0);
  }
  else {
    if (history24<10) {tft.print("0");}
    tft.print(history24,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(20,20,20,204,GREY);

// past 42 hours
  tft.setCursor(42,205);
  history18 = (timeClient.getHours()-18);
  history42 = (timeClient.getHours()-42);
  if (history42 <0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history42 < -24) {tft.setTextColor(CYAN);}
  if (history18 <0){historyC = history18 + 24;}
  if (history18 <0){
    if (historyC<10) {tft.print("0");}
    tft.print(historyC,0);
  }
  else {
    if (history18<10) {tft.print("0");}
    tft.print(history18,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(56,20,56,204,GREY);




//- 36 hours (based on 48 hours)

  tft.setCursor(78,205);
  history12 = (timeClient.getHours()-12);
  history42 = (timeClient.getHours()-36);
  if (history42 <0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history42 < -24) {tft.setTextColor(CYAN);}
  if (history12 <0){historyB = history12 + 24;}
  if (history12 <0){
    if (historyB<10) {tft.print("0");}
    tft.print(historyB,0);
  }
  else {
    if (history12<10) {tft.print("0");}
    tft.print(history12,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(92,20,92,204,GREY);

 
// -30 hours (based on 48 hours)
  tft.setCursor(114,205);
  history6 = (timeClient.getHours()-30);
  if (history6 < 0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history6 <-24) {tft.setTextColor(CYAN);}
  if (history6 <0){historyA = history6 + 24;}
  if (history6 <0){
    if (historyA<10) {tft.print("0");}
    tft.print(historyA,0);
  }
  else {
    if (history6<10) {tft.print("0");}
    tft.print(history6,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(128,20,128,204,GREY);



// -24 hours (based on 48hour trend)
  tft.setCursor(150,205);
  history24 = (timeClient.getHours()-24);
  if (history24 <0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history24 <-24) {tft.setTextColor(CYAN);}
  if (history24 <0){historyD = history24 + 24;}
  if (history24 <0){
    if (historyD<10) {tft.print("0");}
    tft.print(historyD,0);
  }
  else {
    if (history24<10) {tft.print("0");}
    tft.print(history24,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(164,20,164,204,GREY);


// -18 hours (based on 48hour trend)  
  tft.setCursor(186,205);
  history18 = (timeClient.getHours()-18);
  if (history18 <0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history18 <0){historyC = history18 + 24;}
  if (history18 <0){
    if (historyC<10) {tft.print("0");}
    tft.print(historyC,0);
  }
  else {
    if (history18<10) {tft.print("0");}
    tft.print(history18,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(200,20,200,204,GREY);






  tft.setCursor(222,205);
  history12 = (timeClient.getHours()-12);
  if (history12 <0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history12 <0){historyB = history12 + 24;}
  if (history12 <0){
    if (historyB<10) {tft.print("0");}
    tft.print(historyB,0);
  }
  else {
    if (history12<10) {tft.print("0");}
    tft.print(history12,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(236,20,236,204,GREY);
  Serial.print("his12");
  Serial.print (history12);
  Serial.print("hisB");
  Serial.print (historyB);


// -6 hours (based on 48hour trend) xscale = (290 * ((((del+750) / 1000))/60)/60);
  tft.setCursor(258,205);
  history6 = (timeClient.getHours()-6);
  if (history6 <0) {tft.setTextColor(MAGENTA);}
  else {tft.setTextColor(YELLOW);}
  if (history6 <0){historyA = history6 + 24;}
  if (history6 <0){
    if (historyA<10) {tft.print("0");}
    tft.print(historyA,0);
  }
  else {
    if (history6<10) {tft.print("0");}
    tft.print(history6,0);
    }
  tft.print(":");
  if (timeClient.getMinutes() <10)tft.print("0");
  tft.print(timeClient.getMinutes(),1);
  tft.drawLine(272,20,272,204,GREY);


//NOW
  tft.setCursor(300,205);
  tft.drawLine(309,202,309,204,BLACK);
  tft.print("NOW");
  


  tft.setFont(&FreeSans9pt7b); // set font - must be included above at top. https://learn.adafruit.com/adafruit-gfx-graphics-library/using-fonts
  tft.setTextColor(YELLOW);
  tft.setTextSize(1);
  tft.setCursor(200,230);
  tft.print("NOW ");
  tft.print(temp,1);
  tft.print(char(247));            //Deg-C symbol
  tft.print("C");
  temp_readings[reading] = temp;
  
  if (temp > max_temp) max_temp = temp;
  if (temp < min_temp) min_temp = temp;
 
  tft.setTextSize(1);
  // Now display max and min temperature readings
  tft.setTextColor(RED);
  tft.setCursor(10,230);
  tft.print(max_temp,1);
  tft.print(char(247));          // Deg-C symbol
  tft.print("C max");
  tft.setTextColor(CYAN);
  tft.setCursor(100,230);
  tft.print(min_temp,1);
  tft.print(char(251));          // Deg-C symbol
  tft.print("C min");

  tft.setFont();             //reset font
  tft.setTextColor(YELLOW);
  tft.setFont(&FreeSans9pt7b);
  tft.setCursor(120,13);
  tft.setTextSize(1);
  tft.print("Temperature");
 // tft.print(xscale,1);
 // tft.print(" hrs");
  
 
 tft.setFont();//reset font
  

unsigned long currentMillis = millis();
  // Every X number of seconds (interval = 10 seconds) 
  // it publishes a new MQTT message
  if (currentMillis - previousMillis >= interval) {
    // Save the last time a new reading was published
    previousMillis = currentMillis;
    // New temperature readings
    sensors.requestTemperatures(); 
    // Temperature in Celsius degrees
    temp = sensors.getTempCByIndex(0)+ temp_error_offset;
    // Temperature in Fahrenheit degrees
    //temp = sensors.getTempFByIndex(0);
    // Publish an MQTT message on topic esp/ds18b20/temperature
    uint16_t packetIdPub1 = mqttClient.publish(MQTT_PUB_TEMP, 1, true, String(temp).c_str());                            
    Serial.printf("Publishing on topic %s at QoS 1, packetId: %i ", MQTT_PUB_TEMP, packetIdPub1);
    Serial.printf("Message: %.2f \n", temp);
   
}
// Display temperature readings on graph
// DrawGraph(int x_pos, int y_pos, int width, int height, int Y1_Max, String title, float data_array1[max_readings], boolean auto_scale, boolean barchart_mode, int colour)
DrawGraph(20,20,290,180,30,"",temp_readings, autoscale_off,  barchart_off, RED); //YI_Max is the Y scale max figure.

reading = reading + 1;
  if (reading > max_readings) { // if number of readings exceeds max_readings (e.g. 100) then shift all array data to the left to effectively scroll the display left
    reading = max_readings;
    for (int i = 1; i < max_readings; i++) {
      temp_readings[i] = temp_readings[i+1];
      
    }
    temp_readings[reading] = temp;
    
  }

  if (WiFi.status() == 3) {
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:Fail");
  tft.setTextColor(GREEN);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:OK");
  }
  if (WiFi.status() == 6) {
  tft.setTextColor(BLACK);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:OK");
  tft.setTextColor(RED);
  tft.setTextSize(1);
  tft.setCursor(265,10);
  tft.print("WiFi:Fail");
  }


// Prints time in TOP LEFT corner.

tft.setTextColor(YELLOW);
tft.setTextSize(1);
tft.setCursor(1,1); 
tft.print("Last Update:");
tft.print(timeClient.getHours());
tft.print(":");
if (timeClient.getMinutes() <10)tft.print("0");
tft.print(timeClient.getMinutes());




delay(del); //Data logging rate. (allowing 750ms for temp updtate)
  
//tft.fillScreen(BLACK);

  
}






/*  Examples of various display commands
  tft.setTextSize(2); 
  tft.fillScreen(colour);
  tft.setTextColor(txt_colour);
  tft.setCursor(x, y);
  tft.println("text...");
  tft.drawCircle(x,y,diameter,colour);
  tft.fillCircle(x,y,diameter,colour);
  tft.drawRoundRect(x1,y1,x2,y2,curve_diameter,colour);
  tft.drawLine(x1, y1, x2, y2,colour);
  tft.drawChar(x,y,char,bgcolour,color,size);
*/
2

What is going to publish the data to the MQTT broker ?

3

In that function you cannot add the code MQTTclient.subscribe( TheTopicToSUbcribeTo );? Why not?

4

an ispindel Electronic Hydrometer will publish to the MQTT

5

Your first step should be to write a small sketch that subscribes to the topic on the MQTT broker and when the hydrometer publishes data to it, read the data and print it

Forget all about the graphing the data until that works. Have you looked at the examples from the PubSubClient library ? Which Arduino board are you using ?

Is the MQTT broker a local one or is it on the Internet and if so what is its address and the name of the topic to which the data will be published ?

6

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