int ch_pd = 3;

int io0 = 2;

void setup() {

  pinMode(ch_pd, OUTPUT);

  pinMode(io0, OUTPUT);

  digitalWrite(io0, LOW);

  digitalWrite(ch_pd, LOW);

  delay(1000);

  digitalWrite(ch_pd, HIGH);

}

void loop(){

}

#include <SoftwareSerial.h>

SoftwareSerial esp8266(4,5);

void setup() {

  Serial.begin(9600);

  Serial.println("Arduino...OK");

  esp8266.begin(115200);

  esp8266.write("AT+UART_DEF=9600,8,1,0,0\r\n");

  delay(1500);

  esp8266.begin(9600);

  Serial.println("ESP8266...OK");

}

void loop() {

  if (esp8266.available()) {

    Serial.write(esp8266.read());

    }

    if (Serial.available()) {

      esp8266.write(Serial.read());

      }

}