I have a Nexion HMI that i would like to control my PCA9685 Hat, I have Node-Red communicating with the servos and it works nicely, But now i need to control the Flow with a Nexion HMI via a usb UART connection. i cant seem to find anything on the internet to help me.
I don't believe there is a direct way. I think that your display is designed to be controlled at a lower level so you have to send the correct commands to it and build the display from a low-level.
You use Nextion's interface creator programme and upload that direct to the display. From that you get data out of its serial connection that you can then interface to Node-RED.