How to avoid delays in the loop() function?

Question

vI have this functions in my loop() and it publishes temperature reading to Ubidots(an IoT cloud service) using the #include library but it seems it returns a boolean and so the loop is delayed until a true or false value is return and this takes a while there by slowing down my loop() function and other functions in it. Is there a way I can call this function without it having to slow the loop?

#include <math.h>
#include <Wire.h>
#include <Servo.h> 
#include <WiFi.h>
#include <Ubidots.h>
#include "rgb_lcd.h"
#include "Timer.h"
//#include <SoftwareSerial.h>

//SoftwareSerial mySerial(11, 10); // RX, TX


char ssid[] = "ROSTALECOM_6916";                                                 //your network SSID (name) 
char pass[] = "6PTDFYJD";                                                         //your network password (use for WPA, or use as key for WEP)
String api = "875c4a17d995ce4977bdfc1ace55233fd0591c7ce";                             //your API Key number
String idvari = "567d623a762542205cbc517f";                                          //the number of the Ubidots variable
String ctext = "{\"color\":\"blue\",\"status\":\"active\"}";
Ubidots ubiclient(api);                                                             //with that you call the api with the prefix ubiclient

byte p5[8] = {
  0x1F,
  0x1F,
  0x1F,
  0x1F,
  0x1F,
  0x1F,
  0x1F,
  0x1F
  };

int a;
int temperature;
int B=3975;                  //B value of the thermistor
float resistance;

String readString;
int val;
int hum = 70.35;
unsigned char base = 10;

//Temperature Limits
int maxTemp = 29;
int minTemp = 28.5;

//Declarations
rgb_lcd lcd;
Servo winServo;

//Ubidots timer
Timer t;

void setup() 
{    
    //Loading character
    lcd.createChar(0, p5);

Serial1.begin(9600);
Serial.begin(9600); 
winServo.attach(3);
lcd.begin(16, 2);
//mySerial.begin(9600);


//Start Screen
lcd.print("--SmartGarden--");
for (int i = 0; i < 16; i++) 
{
        // scroll one position left:
        lcd.setCursor(i, 1);
        lcd.write((uint8_t)0);
        delay(400);
 }
lcd.clear();
lcd.print("Connecting...");
//connect to  wifi network
boolean response;                                                                
int status = WL_IDLE_STATUS;                                                                                                          
response = ubiclient.WifiCon(ssid, pass, status, api);                            
Serial.println(response);

//
t.every(1000, sendToUbi);

}


void readTemp()
{
   a=analogRead(0);
   resistance=(float)(1023-a)*10000/a;  
   temperature=1/(log(resistance/10000)/B+1/298.15)-273.15;

   //Send temperature via Bluetooth
   Serial.print(temperature);

   //print temperature to LCD
   lcd.clear();
   lcd.setCursor(0,0);
   lcd.print("Tmp:");
   lcd.print(temperature);
   //print humidity to LCD
   lcd.setCursor(8,0);
   lcd.print("Hm:");
   lcd.print("50");

   delay(1000);

}
void writeServo()
 {
  if (val != 0)
  {  
  //val = map(val, 0, 1023, 0, 180);     
  winServo.write(val);                  
  delay(100);    
  } 
 } 

 void sendToUbi()
 {
 ubiclient.save_value(idvari, String(temperature));                                                  //this function is to post to ubidots and return True or False depending on the connection status
 Serial.println("The sensor value " + String(temperature) + " was sent to Ubidots");                //print the sensor value     
 }                    

void timerMax()
{
  for (int i = 0; i < 60; i++) 
  {

   }
   winServo.write(180);
 }

void loop() 
{
  //read temperature
  readTemp();

  //Update ubidots timer
   t.update();

  while (Serial1.available()) {
    delay(3);  
    char c = Serial1.read();
    readString += c; 
  }
  if (readString.length() >0)
    {
      Serial.println(readString);
      delay(15);

       val = readString.toInt();
       if (val != 0)
       {  
       //val = map(val, 0, 1023, 0, 180);     
        winServo.write(val);                  
       delay(100); 
       readString = "";   
       } 
       //writeServo();


    if (readString == "1")     
       {
        digitalWrite(13, HIGH);
       }
     if (readString == "0")
       {
        digitalWrite(13, LOW);
       }
     readString = "";
  } 

  if (temperature >= maxTemp)
  {
    timerMax();

  }

}

Answer 1

How to avoid delays in the loop() function?

The question is why all the delays? Is there some logic missing? What are you trying to design?

Using delays is often a sign of an attempt to synchronize with external events. Wait for additional input, etc.

Let us walk through some of them:

void readTemp()
{
   ...
  delay(1000);
}

What is this about? The function does read an analog input BUT then there is a lot of output to Serial and LCD and last this delay. Why?

void writeServo()
{
  ...                
 delay(100);    
} 

Again the same pattern. Now for your question "delays in the loop()".

void loop() 
{
   readTemp(); // hidden 1000 ms delay

  while (Serial1.available()) {
    delay(3);  
    ... 
  }
  if (readString.length() >0)
  {
     ...
     delay(15);
     ...
     if (val != 0)
     {  
       winServo.write(val);  // Possible hidden 100 ms delay                
       delay(100); 
       ...
     } 
     ...
}

Consider using some logic instead of the delays. There seem to be a common pattern you are using.

Answer 2

As short reply and a general note, there is the millis() function that will be faster than a delay(). It returns the number of milliseconds since the Arduino board began running the current program. You use maths to check if you've waited long enough.

Like this:

  // check to see if it's time to do something; that is, if the
  // difference between the current time and last time you blinked
  // the LED is bigger than the interval at which you want to
  // blink the LED.
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // do something after the waiting interval here

   }

Edit: One should also be aware of Interrupts, but be warned they must be used correctly.