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();
 }
}

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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.