Hello,
Nextion HMI display connected to Arduino Uno: Usually the display is connected to pins 8,9 via softwareserial / NeoICSerial so to keep the USB serial free for debugging and firmware updates.
How to upload new firmware to the Nextion HMI display when the arduino and Nextion display are built in somewhere and you cannot acces the nextion display directly?
I wrote a software for arduino Uno that will just do this: It will read firmware over the USB Serial port and forward all to the nextion HMI display connected .
A PC software is also supplied to upload the .tft file from PC.
Please see the code on GitHub - zweistein22/NextionFWUpload: firmware upload from pc over serial to Arduino Uno connected with softwareserial to nextion display
Andreas