Strange experience with LT7381 display - now what?

Other Hardware Displays
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Back in March I purchased a 5in Hunda LT7381 for Arduino. See this thread for details of the display:

The listing clearly states it is for Arduino so I thought I would be safe buying this. It has an I2C interface as well as a UART interface and came with a USB-to-Serial adapter based on the CH340 chip. Unfortunately I couldn't get it to work.

The seller provided links to and test Arduino sketch as well as a program called Visual LCD Studio. I compiled and uploaded the Arduino sketch to a Nano, connected the display, plugged in the USB lead and .... nothing.

I then tried installing the Visual LCD Studio program. This installed fine although I did find that some controls have spelling errors. Undeterred, I opened the example project and successfully compiled and uploaded it to the display. Nothing appeared on the display, although it did show "Downloading..." during the upload process. The application has a button that shows whatever is in the program design window on the display, but still nothing showed. I ran through the process several times checking each step before finally giving up.

Assuming the LCD was faulty I started a refund. Here is where things get a bit weird. I had to send the LCD back to China and the the last I heard was that the refund would be issued once the supplier receives the item back. Fast forward 6 months to the end of September and the package arrives battered, bruised and split open in the post. The contents are still within it and on the package there is a sticker in both Chinese and English stating delivery had been refused. I contact eBay an discover that a refund had been issued some time ago and the case is closed. Not had this happen before.

Thinking that I will probably keep the adapter and leads and throw the LCD, I thought nevertheless to give it another test. I connected it to a spare UNO this time, uploaded the sketch and still nothing. However, by chance I then opened the Serial Monitor - something I had no real reason to do - and to my astonishment the display sprung to life showing the icons featured in the listing images! Apparently, opening a serial connection triggers the program to show the display!

It seems then, that the display is actually working and the problems are with the demo sketch and the Visual LCD Studio software. Since the display seems to be working, I will probably explore this a bit further and take a closer look at how the Arduino program works.

I had already purchased another display for my project and have been using the Bodmer TFT_eSPI library which works nicely. However, as this LT7381 display is I2C, I was wondering whether whether there is an equivalent of the Bodmer library for I2C, or a specific library that supports the LT7381 chip? I would also be interested to hear from anyone who might have successfully used this display with an Arduino or ESP, and if so, what libraries and resources were required to make it work?

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It is not a good idea to believe what you read on an eBay seller's site. There is no quality control whatsoever, and a very large fraction of the cheap stuff from China consists of counterfeits, rejects and recycled parts.

Sometimes the items work fine, so it may be worth taking the chance.

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I do take your point, but there are quite a few of these listed in various sizes. They are not exactly cheap either, although definitely cheaper than, say, a genuine Nextion.

I had a look at the demo sketch and driver files. The basics are there, at least enough to show the demo graphics and some animation. There also appear to be some functions to draw rectangles and print text etc but these do not appear to be used in the demo. There are also a number of areas where it is apparent that both demo sketch and driver are incomplete and plans were laid for further features. Although the library is dated 2014, I couldn't find an updated version.

Still, there might be enough for me to work with here. The library comes with a separate Wire.h/Wire.cpp, I2C.h/I2C.cpp or twi.h/twi.cpp files, depending on which example one looks at. Since these days one just needs to include <Wire.h> in the sketch, some work will be required to make it compatible with the default Arduino Wire library. In addition, the calls will need documenting and then maybe missing features added. I might have a go at the first two items if I have time.

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