I have built an energy meter system using arduino and nextion display. But iam having a problem with changing the GUI dynamically as per the user's requirement. AT present, I have to disconnect the display unit, modify the sd card contents, assemble the unit again and subsequently change the arduino code for it to work. If GUI is not satisfactory, I have to dismantle the unit again. Is there any alternate method where I could change the contents of the sd card online similar to arduino?
You can program a Nextion through its serial port directly from the IDE. To do this you need a serial port connected to the Nextion, then you can upload to it. Obviously this doesn't quite meet your requirements because you still have to wire a serial port to the Nextion. Maybe some code on the Arduino could send serial data from your PC to the Nextion. I did try this unsuccessfully but I didn't put much effort into finding out why it didn't work, so don't let my failure put you off. Another option might be a physical switch to switch the Nextion serial port between the Arduino and a serial port on your PC.
But should I not store the GUI in SD Card?
The Nextion doesn't store its configuration on the SD card, that's just used as a way to transfer the configuration from the PC to the Nextion.
How is the Nextion packaged in the energy meter system.
I have always designed the units so the sd card slot is accessible so that reprogramming the Nextion does not require any disassembly.
Nextion is packaged on an enclosure. Serial port is internally connected to Arduino. I do not understand, how to engineer the configurability (PC vs arduino). I cannot provide any switch in the front panel as it goes against the users requirement. Please guide me towards good options
Can you package the Nextion so that the SD slot is accessible through a slit in the side of the enclosure.
This is an model of a 2.8" Nextion in a battery powered wireless remote control unit. The Nextion serial rx/tx are connected to an HC=12 module and there is a complementary HC=12 on Serial1 of a Nano Every. Note the access slot on the enclosure.
I think, I might have to resort to a multiplexer that either routes the data between PC or arduino. Selection is done through a switch
You can have different pages with Nextion display , so you could have a simple jpg on the sd card and modify its look with additional lines boxes , text, for each page.
This might be wrong but ….
Can’t recall , been a couple of years since I played with these ,but you may be able to change which image is loaded at boot by having different named images . Store name in epprom , force a restart with watchdog timer and load what ever image the epprom indicates ??
Intelligent nextions can be used as a dynamic photo frame - worth a google for how that works