user19910: I want to connect an Esp8266 Wifi module to an Arduino nano. I am wondering if I need to implement level-shifting for the Arduino TX line to Esp RX line?
I find different schema's on the net. Some with, some without level-shifting:
With:
http://community.blynk.cc/t/robot-with-esp8266-shield-and-arduino-nano/3316/8
Without:
Arduino Nano v3.0 with ESP8266
Some use a capacitor between GND and Esp CH_PD pin, others use a 10K resister between the 3.3V and the CH_PD pin (https://blogs.msdn.microsoft.com/abhinaba/2016/01/23/esp8266-wifi-with-arduino-uno-and-nano/)...
What is the most basic but required setup for a Arduino Nano and a Esp8266?
(I have Esp8266-12e modules)
Thanks!

user1675: The arduino nano v3's logic is 5v, and the ESP8266's logic is 3.3V, so you need to do level shifting between both.
Using a voltage divider drains more current (guess not an issue in this case) and it's ok only when going from 5V to 3.3V (when the signal must be shifted from 3.3V to 5V in the links you provide, it looks like it's based on that 3.3V is still considered "HIGH" on a TTL signal). 
I personally prefer using a level shifter, it just complicates a bit the Bill Of Materials, but you won't have to debug the level shifting part.
And better than that, using an arduino mini pro @3.3v working directly at 3.3V gets rid of this hassle.

user2881: You could use a simple diode, between the Arduino TX and ESP RX. That's what the Adafruit Huzzah uses.
It takes advantage of the internal pull-up on the RX pin of the ESP. The diode will allow a LOW, to pull the signal low, through the diode. But it will block a HIGH 5 Volt signal from going into the ESP.

19910: <p>I want to connect an Esp8266 Wifi module to an Arduino nano. I am wondering if I need to implement level-shifting for the Arduino TX line to Esp RX line?</p>

<p>I find different schema's on the net. Some with, some without level-shifting:</p>

<p>With:
<a href="http://community.blynk.cc/t/robot-with-esp8266-shield-and-arduino-nano/3316/8" rel="nofollow noreferrer">http://community.blynk.cc/t/robot-with-esp8266-shield-and-arduino-nano/3316/8</a></p>

<p>Without:
<a href="https://arduino.stackexchange.com/questions/17590/arduino-nano-v3-0-with-esp8266">Arduino Nano v3.0 with ESP8266</a></p>

<p>Some use a capacitor between GND and Esp CH_PD pin, others use a 10K resister between the 3.3V and the CH_PD pin (<a href="https://blogs.msdn.microsoft.com/abhinaba/2016/01/23/esp8266-wifi-with-arduino-uno-and-nano/" rel="nofollow noreferrer">https://blogs.msdn.microsoft.com/abhinaba/2016/01/23/esp8266-wifi-with-arduino-uno-and-nano/</a>)...</p>

<p>What is the most basic but required setup for a Arduino Nano and a Esp8266?
(I have Esp8266-12e modules)</p>

<p>Thanks!</p>
 1675: <p>The <strong>arduino nano v3</strong>'s logic is 5v, and the ESP8266's logic is 3.3V, so you need to do level shifting between both.
Using a voltage divider drains more current (guess not an issue in this case) and it's ok only when going from 5V to 3.3V (when the signal must be shifted from 3.3V to 5V in the links you provide, it looks like it's based on that 3.3V is still considered "HIGH" on a TTL signal). </p>

<p>I personally prefer using a level shifter, it just complicates a bit the Bill Of Materials, but you won't have to debug the level shifting part.</p>

<p>And better than that, using an arduino mini pro @3.3v working directly at 3.3V gets rid of this hassle.</p>
 2881: <p>You could use a simple diode, between the Arduino TX and ESP RX. That's what the <a href="https://cdn-learn.adafruit.com/assets/assets/000/024/745/original/adafruit_products_schem.png?1429900999" rel="nofollow">Adafruit Huzzah uses</a>.</p>

<p>It takes advantage of the internal pull-up on the RX pin of the ESP. The diode will allow a LOW, to pull the signal low, through the diode. But it will block a HIGH 5 Volt signal from going into the ESP.</p>
