Nextion - controllino mini (Arduino uno) communication issue

So, i have been working with nextion display enhanced version and controllino mini(Arduino uno) or controllino maxi automation (arduino mega) for almost 2 years. I have made a few projects that work really well and one day suddenly only one side of communication works (from arduino to display)
this is third day i am trying to figure it out and im at the end. I have no other ideas why it works just one sided. i have tried using old microcontroller or old display it just doesnt work. only old projects work. I took old nextion display from my project uploaded same code to it and now communication doesnt work on that project. I dont think that theres issue with my code but it could be there. I have made a simple code but the results were the same (it only works from arduino to nextion) It just doesnt make sense why it would work only on one side - that means that baudrate is the same that configuration is ok and so on...

The obvious answer, the one you don't want to hear, is that the Nextion Tx pin is faulty in some way. Baud rate is the same both ways, no way to make it different. Do you have an oscilloscope to look at the data from the Nextion? Serial is high when idle and pulses low for data. If you don't have an oscilloscope then try an LED with a 1k Ohm resistor:
Disconnect the Nextion Tx from the Arduino Rx
Put the LED - resistor between the Nextion Tx* and 0V, it should be on. Try sending something from the Nextion, you should see it flicker (maybe).
Put the LED - resistor between the Nextion Tx* and +5V, it should be off. Try sending something from the Nextion, it should flicker on.
This works best with the baud rate as low as possible.

  • Make sure you get the polarity right or the LED will just be off all the time.