user11019: I am integrating Arduino Uno with the WiFi module ESP8266.  I have already made the connections between the ESP8266 and the Arduino Uno which are :
txd uno -> rxd esp8266 
rxd uno -> txd esp8266  
gnd uno -> gnd esp8266

The VCC and chid pind of ESP8266 are connected to an external supply of voltage 3.3V and 160mA current. The code is getting uploaded onto the Arduino and the ESP8266 is also getting powered on.But i am facing a problem while i send the AT commands on the serial monitor. It is not responding even though the red led is on constantly and when i press enter after sending the command , the blue led blinks for a few seconds.
Do i have to update the firmware of the ESP8266?

user8033: Okay, I'll just summarize the stuff I've seen in the comments and answers. It's quite a basic issue? You'll find a lot resources on it on the web.
Current (draw of chip too high?):
Wireless communication can take a lot of current. You should have a good power supply. Arduino usually can't supply enough current. Check the datasheet of the chip to see it max current draw.
Rx/Tx (Wiring):
Be sure you send through the Tx pin, into the Receive (Rx) pin of the other device.
Also, you can't use the same Tx pins for USB communication AND to connect to the ESP, that basically won't work.
Voltage (3.3V vs 5V):
The arduino runs on 5V, but, the ESP on 3.3V you shouldn't want to mix these up.
It'll do in some cases. Putting 3.3V (Tx of ESP) on the Rx of arduino (5V) won't damage it. But the other way around is strongly discouraged. Use a logic level shifter or voltage divider between it.
Chip might be broken
If the chip isn't doing anything at all, you should take in consideration that it's possible the chip is broken... I've spent too many hours on debugging my code while the chip simply wasn't working. Also after having applied 5V to the ESP8266, this becomes quite likely.

user32933: We had a similar issue and landed up spending a lot of time figuring out what was going wrong, the following certainly helped us resolve the issue:

We set the Baud rate of the Serial communication to 1200. This started showing the responses from ESP correctly with no / minimal junk
We set the baud rate of communication with ESP to 115200. This ensured that the ESP received correct commands.
We ensured that each command we send is terminated by a CR for e.g. ESP8266.println(espCmd + "\r"); // where ESP8266 is SoftwareSerial ESP8266 (rxPin, txPin);
Also, powering the ESP module with 5V gave no responses from ESP. When we powered it with 3.3V only then it started to provide any response - initially response looked like junk due to mismatched baud settings.

Hope this helps.
(Sometime you may need to use both \r\n....)
Regards

user14623: I had same problem. It helped to connect GNDs of both power supplies namely the one powering the arduino and the 3.3V one powering the ESP8266.

11019: <p>I am integrating Arduino Uno with the WiFi module ESP8266.  I have already made the connections between the ESP8266 and the Arduino Uno which are :</p>

<pre><code>txd uno -&gt; rxd esp8266 
rxd uno -&gt; txd esp8266  
gnd uno -&gt; gnd esp8266
</code></pre>

<p>The VCC and chid pind of ESP8266 are connected to an external supply of voltage 3.3V and 160mA current. The code is getting uploaded onto the Arduino and the ESP8266 is also getting powered on.But i am facing a problem while i send the AT commands on the serial monitor. It is not responding even though the red led is on constantly and when i press enter after sending the command , the blue led blinks for a few seconds.
Do i have to update the firmware of the ESP8266?</p>
 8033: <p>Okay, I'll just summarize the stuff I've seen in the comments and answers. It's quite a basic issue? You'll find a lot resources on it on the web.</p>

<p><strong>Current (draw of chip too high?):</strong></p>

<p>Wireless communication can take a lot of current. You should have a good power supply. Arduino usually can't supply enough current. Check the datasheet of the chip to see it max current draw.</p>

<p><strong>Rx/Tx (Wiring):</strong></p>

<p>Be sure you send through the Tx pin, into the Receive (Rx) pin of the other device.
Also, you can't use the same Tx pins for USB communication AND to connect to the ESP, that basically won't work.</p>

<p><strong>Voltage (3.3V vs 5V):</strong></p>

<p>The arduino runs on 5V, but, the ESP on 3.3V you shouldn't want to mix these up.
It'll do in some cases. Putting 3.3V (Tx of ESP) on the Rx of arduino (5V) won't damage it. But the other way around is strongly discouraged. Use a logic level shifter or voltage divider between it.</p>

<p><strong>Chip might be broken</strong></p>

<p>If the chip isn't doing anything at all, you should take in consideration that it's possible the chip is broken... I've spent too many hours on debugging my code while the chip simply wasn't working. Also after having applied 5V to the ESP8266, this becomes quite likely.</p>
 32933: <p>We had a similar issue and landed up spending a lot of time figuring out what was going wrong, the following certainly helped us resolve the issue:</p>

<ol>
<li>We set the Baud rate of the Serial communication to 1200. This started showing the responses from ESP correctly with no / minimal junk</li>
<li>We set the baud rate of communication with ESP to 115200. This ensured that the ESP received correct commands.</li>
<li>We ensured that each command we send is terminated by a CR for e.g. ESP8266.println(espCmd + "\r"); // where ESP8266 is SoftwareSerial ESP8266 (rxPin, txPin);</li>
<li>Also, powering the ESP module with 5V gave no responses from ESP. When we powered it with 3.3V only then it started to provide any response - initially response looked like junk due to mismatched baud settings.</li>
</ol>

<p>Hope this helps.</p>

<p>(Sometime you may need to use both \r\n....)</p>

<p>Regards</p>
 14623: <p>I had same problem. It helped to connect GNDs of both power supplies namely the one powering the arduino and the 3.3V one powering the ESP8266.</p>
