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.

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  • esp8266 SoftwareSerial doesn't work reliably
    – Juraj
    Oct 10, 2018 at 18:33
  • @Juraj: Thanks. Can I use default Tx and Rx? are those reliable?
    – Learner
    Oct 10, 2018 at 18:38
  • yes of course. esp8266 has second hw Serial interface, but only TX of it can be used
    – Juraj
    Oct 10, 2018 at 18:42
  • That means I can transmit data to Atmega328 but could not get it back.
    – Learner
    Oct 10, 2018 at 18:46
  • low pulse is being generated where is it being generated?
    – jsotola
    Oct 10, 2018 at 20:01

1 Answer 1


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.

  • Many thanks Juraj. It’s solved our problem. Many many thanks as we are struggling with this quite many days.
    – Learner
    Oct 11, 2018 at 15:21

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