user50229: Thanks in advance..
We are having esp8266-12E chip and Atmega328 connected as follows, 
ESP 12 pin as Tx,13 pin as Rx && Atmega328 13pin as Rx, 12pin as Tx. Everything works fine, but while communicating via serial some low pulse is being generated. We couldn't find the issue with multimeter anyway but got it by oscilloscope signal.
When this false low pulse during communication happens Atmega328 connected pins also getting low for the same duration.
We tried using separated logic execution for ESP and Atmega and both were worked perfectly, but only during communicating via Software serial its flickers getting started. 
Please help us getting this resolved.


user37622: Don't use SoftwareSerial in esp8266. Connect the 328p's SoftwareSerial pins to Serial interface pins of the esp8266. ESP8266 has second Serial interface named Serial1. It has only TX (io 2), but it is enough for debug prints.
To change the firmware or sketch in esp8266 you can use ArduinoOTA library, but you should be ready to disconnect the esp8266 Serial pins from the 328p and use them for Serial upload if the OTA upload fails.
You should use logic level converter from 5 V to 3.3 V to protect the esp8266 RX pin. 

50229: <p>Thanks in advance..</p>

<p>We are having esp8266-12E chip and Atmega328 connected as follows, 
ESP 12 pin as Tx,13 pin as Rx &amp;&amp; Atmega328 13pin as Rx, 12pin as Tx. Everything works fine, but while communicating via serial some low pulse is being generated. We couldn't find the issue with multimeter anyway but got it by oscilloscope signal.</p>

<p>When this false low pulse during communication happens Atmega328 connected pins also getting low for the same duration.</p>

<p>We tried using separated logic execution for ESP and Atmega and both were worked perfectly, but only during communicating via Software serial its flickers getting started. </p>

<p>Please help us getting this resolved.</p>

<p><a href="https://i.stack.imgur.com/IteHq.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IteHq.jpg" alt="enter image description here"></a></p>
 37622: <p>Don't use SoftwareSerial in esp8266. Connect the 328p's SoftwareSerial pins to Serial interface pins of the esp8266. ESP8266 has second Serial interface named Serial1. It has only TX (io 2), but it is enough for debug prints.</p>

<p>To change the firmware or sketch in esp8266 you can use ArduinoOTA library, but you should be ready to disconnect the esp8266 Serial pins from the 328p and use them for Serial upload if the OTA upload fails.</p>

<p>You should use logic level converter from 5 V to 3.3 V to protect the esp8266 RX pin. </p>
