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Using the Nextion display: Hit a issue Part 2

A project log for Building the Thor robot

Building a 6-axis robot based on the Thor robot. When size DOES matter!

Olaf Baeyens 08/21/2017 at 20:492 Comments

This weekend I hit an issue when I tested my Thor controller code in combination with my Nextion display that drives me nuts.

Because I have a 5V to 3.3V converter I hooked up the logic analyzer to see if I had issues with noise.

Conclusion: I do not have a signal noise issue.


I press the E0 button, the Nextion display sends a command to the Thor controller. Above is the 5V digital and in blue its 5V analog signal.

Lower the 3.3V digital and below that its analog signal.

Conclusion it is very clear that the Thor controller receives the signal and should trigger the callbacl function by sending back something. But nothing happens also the debug LED does not pop up.


A second test with a different button makes me confused.

I press the rotation buttons 2 buttons below the E0 (digital signal in the middle. You clearly see the Thor controller responding. But what is weird is what is in front of it. That is the button down press of the E0 button I did not press.

When I test them on the other rotate buttons I never get this E0, E1, E2....  in front of it what is different?

The transmitted test text to see if the callback gets triggered  seems to be clear text: 'b14.txt="text_2"' in the logic analyzer output.

Discussions

Olaf Baeyens wrote 08/26/2017 at 23:35 point

Mystery solved, the dual state button implementation by Nextion for the Arduino seems to react when you do the "Touch release event" not on the "Touch press event". I see the Touch press event passing using the logic analyzer.

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Olaf Baeyens wrote 08/21/2017 at 21:14 point

I just noticed, that the signal voltage levels coming from the 5V Nextion display is very similar in voltage after the 5V/3.3V signal converter. I initially thought I measured the same signal but when you zoom in you see that it is a different signal.

This 7 Inch display may be compatible for 5V and 3.3V at the same time. Maybe the Nextion display operates at 3.3V itself.

Someone with a oscilloscope could verify this.

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