user14603: I am working on esp8266 with Arduino. 
I have connected pins like arduino-esp 3.3-vcc
gnd-gnd 3.3-CH_PD RX-TX TX-RX  and reset to gnd using 3k resistor. 
I couldn't send AT commands in serial monitor in Arduino IDE. 
Later I connected a capacitor between Vcc and Gnd. Now I could send AT commands and I am getting same commands back. Whatever I entered, I am getting the same back.
I didn't get reply as OK. And I got some random characters too. Can anyone help me with this?

user14130: Looks like your connection is somewhere missing.
Connect CH_PD and reset pin to high--i.e. 3.3v.

user38107: I made the following connection with Arduino Mega 2560 and AT commands was working perfectly well.
Connection:
ESP8266 - Arduino Mega 2560
Vcc, CH_PD, RST - 3.3V pin
GND - GND
Rx - Tx(18)
Tx - Rx(19)
Program:
void setup() {
  Serial.begin(115200);   // USB serial port of Due (PROGRAMMING)
  Serial1.begin(115200);  // ESP8266 on Serial Port 1 of Due (UART 1)
}

char rx_byte = 0;

void loop() {
  // send terminal byte to ESP8266
  if (Serial.available() > 0) {
    rx_byte = Serial.read();
    Serial1.print(rx_byte);
  }
  // send ESP8266 byte to terminal
  if (Serial1.available() > 0) {
    rx_byte = Serial1.read();
    Serial.print(rx_byte);
  }
}

Select Tools>Board> Arduino/Genuino Mega or Mega 2560. Upload the code. In serial monitor, select 115200 baud rate and Both NL & CR option.
Enter the AT command and it works!

14603: <p>I am working on esp8266 with Arduino. </p>

<p>I have connected pins like arduino-esp 3.3-vcc
gnd-gnd 3.3-CH_PD RX-TX TX-RX  and reset to gnd using 3k resistor. </p>

<p>I couldn't send AT commands in serial monitor in Arduino IDE. </p>

<p>Later I connected a capacitor between Vcc and Gnd. Now I could send AT commands and I am getting same commands back. Whatever I entered, I am getting the same back.</p>

<p>I didn't get reply as OK. And I got some random characters too. Can anyone help me with this?</p>
 14130: <p>Looks like your connection is somewhere missing.</p>

<p>Connect CH_PD and reset pin to high--i.e. 3.3v.</p>
 38107: <p>I made the following connection with Arduino Mega 2560 and AT commands was working perfectly well.</p>

<p><strong>Connection:</strong></p>

<p>ESP8266 - Arduino Mega 2560</p>

<p>Vcc, CH_PD, RST - 3.3V pin</p>

<p>GND - GND</p>

<p>Rx - Tx(18)</p>

<p>Tx - Rx(19)</p>

<p><strong>Program:</strong></p>

<pre><code>void setup() {
  Serial.begin(115200);   // USB serial port of Due (PROGRAMMING)
  Serial1.begin(115200);  // ESP8266 on Serial Port 1 of Due (UART 1)
}

char rx_byte = 0;

void loop() {
  // send terminal byte to ESP8266
  if (Serial.available() &gt; 0) {
    rx_byte = Serial.read();
    Serial1.print(rx_byte);
  }
  // send ESP8266 byte to terminal
  if (Serial1.available() &gt; 0) {
    rx_byte = Serial1.read();
    Serial.print(rx_byte);
  }
}
</code></pre>

<p>Select Tools>Board> Arduino/Genuino Mega or Mega 2560. Upload the code. In serial monitor, select 115200 baud rate and Both NL &amp; CR option.
Enter the AT command and it works!</p>
