Has anyone tried the upload program from the nextion library with arduino?
Can anyone from ITEAD give me few hints on to get it working'''
Also, does it require an additional SD card to load the tft file? How does it work?
The upload protocol is a bit more of an advanced application used for swapping TFT files (compiled HMIs) out on the fly. As such, this would need to be done from the MCU side via serial.
Few MCUs (such as the Intel Edison) have their own storage sufficient to house multiple TFTs (my Edison has something like 2.7GB of user space). MCUs such as an Arduino Mega2560 would indeed require an MCU side SD.
NexUpload.cpp is an implementation of the Upload protocol, similar to what you see occurring within the Nextion Editor. The details of the Upload protocol can be seen implemented in the code, or in the Itead Blog posting where the Upload protocol was publically published.
Blog : Nextion HMI Upload Protocol (blog post)