Connecting esp8266 using Arduino I am trying to connect to esp8266 using Arduino UNO. There are various things on the internet having mixed information and hence I am seeking some clarity.

I followed these instructions, but could not get to connect to ESP8266 using AT command. http://cordobo.com/2300-flash-esp8266-01-with-arduino-uno/

I have following questions:


Can I connect ESP8266 directly to Tx/Rx without voltage divider or level shifter? I also suspect that the voltage divider connections are wrong. As per my understanding, the Tx from Arduino should be divided, and the divider output should be connected to ESP8266.
When I connected the shield as described, the shield gets hot. Is there any way to conclude if the shield is damaged or not?
When I connect the device using voltage divider the blue LED on the shield also lights up. Without divider, it does not light up. What is the significance of the blue LED?


Hardware

ESP8266-01 pinout



Circuit using voltage divider



Circuit without voltage divider
There are a number of issues with the tutorial you've listed there.

Firstly, a voltage divider is very highly recommended as the ESP8266 cannot handle more than 3.3V, however, the connections for the voltage divider in the tutorial you linked to are the wrong way round (as you suspected).

Secondly, you cannot power the ESP8266 directly from the Arduino, as the power requirements are higher than the Arduino's on board 3.3V regulator. A separate power supply or regulator is recommended. This might be cause of it getting hot (the onboard regulator maybe - but I can't be sure as there is not enough information from your initial post as to exactly what is getting hot).

There are 2 LED's on the ESP8266 shield (the one used in the tutorial you've linked to) one is power and the blue one is wifi communication.

The other potential issue with the tutorial you've linked to is that they have used Arduino pins 0 and 1 to connect to the ESP8266 - while this will work, the problem is that the Arduino uses pins 0 and 1 to communicate over USB with a computer, which means that in in that configuration you cannot use Serial monitor to send/receive data.