How to optimize arduino code?

Question

Arduino

Good time of the day. How can I increase the speed of code execution in arduino?
Actually the code itself:

#include <SoftwareSerial.h>
SoftwareSerial ESPport(2, 3); 
////////////////////// RX, TX

// если у вас MEGA, то закомментируйте верхние две строчки и раскомментируйте нижеследующую.
// ESP подключите к Serial1 (18, 19), скорость можно сделать 57600
// HardwareSerial & ESPport = Serial1;

const int r1 =  4;
const int r2 =  5;
const int r3 =  6;
const int r4 =  7;           
int r1State = HIGH;
int r2State = HIGH;           
int r3State = HIGH;
int r4State = HIGH;
#define BUFFER_SIZE 128
char buffer[BUFFER_SIZE];
String vklotkl1;
String vklotkl2;
String vklotkl3;
String vklotkl4;
 
void setup() 
{ 
  pinMode(r1, OUTPUT); 
  pinMode(r2, OUTPUT); 
  pinMode(r3, OUTPUT); 
  pinMode(r4, OUTPUT);        
  Serial.begin(9600); // Терминал
  ESPport.begin(9600); // ESP8266  
  clearSerialBuffer();
  Serial.println("RESET 3,5 sek");
  delay(200);
  Serial.println(GetResponse("AT+RST",3400)); // перезагрузка ESP
  delay(200);
  Serial.println(GetResponse("AT+CWMODE=1",300)); // режим клиента
  delay(200);
  Serial.println(GetResponse("AT+CSYSWDTENABLE",300)); // сторож   
  delay(20);
  connectWiFi("testap","passfortestap"); // подключаемся к домашнему роутеру (имя точки, пароль) 
  delay(200);
  Serial.println(GetResponse("AT+CIPMODE=0",300)); // сквозной режим передачи данных. 
  delay(200);
  Serial.println(GetResponse("AT+CIPMUX=1",300)); // multiple connection.
  delay(200);
  Serial.print("Start TCP-server: ");
  delay(200);
  Serial.println(GetResponse("AT+CIPSERVER=1,88", 300)); // запускаем ТСР-сервер на 88-ом порту
  delay(200);
  Serial.println(GetResponse("AT+CIPSTO=2", 300)); // таймаут сервера 2 сек
  delay(200);
  Serial.println(GetResponse("AT+CIFSR", 300)); // узнаём адрес
  delay(200);
  digitalWrite(r1,r1State);
  digitalWrite(r2,r2State);
  digitalWrite(r3,r3State);
  digitalWrite(r4,r4State);
}
///////////////////основной цикл, принимает запрос от клиента/////////////////// 
void loop() 
{
 int ch_id, packet_len;
 char *pb;  
 ESPport.readBytesUntil('\n', buffer, BUFFER_SIZE);
  
 if(strncmp(buffer, "+IPD,", 5)==0) 
  {
   sscanf(buffer+5, "%d,%d", &ch_id, &packet_len);
   if (packet_len > 0) 
    {
      pb = buffer+5;
      while(*pb!=':') pb++;
      pb++;
      
      if(strncmp(pb, "GET / ", 6) == 0)
       {
        clearSerialBuffer();
        otvet_klienty(ch_id);
       }      
      
      //r1
      if(strncmp(pb, "GET /a", 6) == 0)
       {
        clearSerialBuffer();
        
        if(r1State == LOW) 
          {
            r1State = HIGH;
            vklotkl1 = "VKL";
          }
        
        else 
          {
            r1State = LOW;
            vklotkl1 = "OTKL";
          } 
        
        digitalWrite(r1, r1State);
        otvet_klienty(ch_id);
       } 
       
      //r2 
      if(strncmp(pb, "GET /b", 6) == 0)
       {
        clearSerialBuffer();
        
        if(r2State == LOW) 
          {
            r2State = HIGH;
            vklotkl2 = "VKL";
          }
        
        else 
          {
            r2State = LOW;
            vklotkl2 = "OTKL";
          } 
        
        digitalWrite(r2, r2State);
        otvet_klienty(ch_id);
       }   
  
      //r3
      if(strncmp(pb, "GET /c", 6) == 0)
       {
        clearSerialBuffer();
        
        if(r3State == LOW) 
          {
            r3State = HIGH;
            vklotkl3 = "VKL";
          }
        
        else 
          {
            r3State = LOW;
            vklotkl3 = "OTKL";
          } 
        
        digitalWrite(r3, r3State);
        otvet_klienty(ch_id);
       }       

//r4
      if(strncmp(pb, "GET /d", 6) == 0)
       {
        clearSerialBuffer();
        
        if(r4State == LOW) 
          {
            r4State = HIGH;
            vklotkl4 = "VKL";
          }
        
        else 
          {
            r4State = LOW;
            vklotkl4 = "OTKL";
          } 
        
        digitalWrite(r4, r4State);
        otvet_klienty(ch_id);
       }       

       
    }
  }
  clearBuffer();
}
//////////////////////формирование ответа клиенту////////////////////
void otvet_klienty(int ch_id) 
{
  String Header;

  Header =  "HTTP/1.1 200 OK\r\n";
  Header += "Content-Type: text/html\r\n";
  Header += "Connection: close\r\n";  
  
  String Content;
  
  Content = "<html><body>";
  Content += "<form action='a' method='GET'>r1 <input type='submit' value='VKL/OTKL'> " + vklotkl1 + "</form>";
  Content += "<form action='b' method='GET'>r2 <input type='submit' value='VKL/OTKL'> " + vklotkl2 + "</form>";
  Content += "<form action='c' method='GET'>r3 <input type='submit' value='VKL/OTKL'> " + vklotkl3 + "</form>";
  Content += "<form action='d' method='GET'>r4 <input type='submit' value='VKL/OTKL'> " + vklotkl4 + "</form>";
  Content += "</body></html>";
  
  Header += "Content-Length: ";
  Header += (int)(Content.length());
  Header += "\r\n\r\n";
  
  ESPport.print("AT+CIPSEND="); // ответ клиенту
  ESPport.print(ch_id);
  ESPport.print(",");
  ESPport.println(Header.length()+Content.length());
  delay(20);

  if(ESPport.find(">")) 
    {
      ESPport.print(Header);
      ESPport.print(Content);
      delay(200); 
    }
}
/////////////////////отправка АТ-команд/////////////////////
String GetResponse(String AT_Command, int wait)
{
  String tmpData;
  
  ESPport.println(AT_Command);
  delay(wait);
  while (ESPport.available() >0 )  
   {
    char c = ESPport.read();
    tmpData += c;
    
    if ( tmpData.indexOf(AT_Command) > -1 )         
      tmpData = "";
    else
      tmpData.trim();       
          
   }
  return tmpData;
}
//////////////////////очистка ESPport////////////////////
void clearSerialBuffer(void) 
{
       while ( ESPport.available() > 0 ) 
       {
         ESPport.read();
       }
}
////////////////////очистка буфера//////////////////////// 
void clearBuffer(void) {
       for (int i =0;i<BUFFER_SIZE;i++ ) 
       {
         buffer[i]=0;
       }
}
////////////////////подключение к wifi/////////////////////        
boolean connectWiFi(String NetworkSSID,String NetworkPASS) 
{
  String cmd = "AT+CWJAP=\"";
  cmd += NetworkSSID;
  cmd += "\",\"";
  cmd += NetworkPASS;
  cmd += "\"";
  Serial.println(cmd); 
  Serial.println(GetResponse(cmd,6500));
}

I wish it was faster and weighed less.

Answer 1

1) Work with an array, not with variables r1, r2, etc. This will allow the use of loops.
2) Move all string constants to PROGMEM. This will save a lot of RAM.

Answer 2

1) Get rid of tons of ifs with strncmp. You check a lot of superfluous enough to check the last character.
2) I think it is possible to optimize string concatenation, but I'm not sure about the implementation of String - how is it with allocations.