I’ve been experimenting with various ways to display information on my PiStar based hotspot, including the small OLED displays.
I found the the OLED is to far to small, so I splashed out and bought what I thought was an official Nextion 2.4 inch display, from a eBay vendor.
I was aware that there are clones of the Nextion, which don’t work with the official Nextion editor and don’t accept data files produced by the official Nextion editor.
But I specifically ordered a board which looked like a Nextion made by Itead and had a Nextion part number (beginning with NX)
The photo on the product I ordered looked like this.
When the display arrived, I noticed that the PCB did not match the photo in the eBay listing, but it did have the correct model number and also had what looked like the Nextion logo.
Clearly the board is completely different, despite seeming to have identical model numbers.
I became suspicious about whether this board was an authentic Nextion, when I was unable to upload the “TFT” configuration files via SD card.
The upload always stopped whilst displaying “SD Card Update…..” rather than going on to copy the graphics and configuration data from the SD card.
Assuming there was something wrong with the “TFT” file I got from the web, tried connecting the display via a USB to serial converter to my PC, and I managed to use the official Nextion editor to upload a set of screens I downloaded from the MMDVM github account (G4KLX)
The display then seemed to work OK with PiStar, but I thought I’d try a different screen layout, and this is when the problems started …
When I tried to upload the new layout using the Nextion editor and the USB to serial adaptor, I found that the Nextion editor would no longer connect to the display.
However, when I reconnected it to Pi Star, I found it was still working.
Not to be deterred, I thought I’d try to upload via SD card again, and after trying various micro SD cards, I eventually found an old 4Gb card, which was probably 4 years old, which was recognised by the display, and I was able to upload a different layout.
After removing the SD card and removing and reconnecting the 5v input to the Nextion, the new layout worked OK, but unfortunately this was the last time I was able to use the display.
Because I thought I’d try another different screen layout, and after uploading that layout using the micro SD card, when I removed the SD card and removed and reconnected the 5v input to the “Nextion”, I found it was no longer receiving any data from PiStar.
Just in case something had happened to my hotspot board, I connected the USB serial adaptor to the Nextion output on the hotspot and used a terminal program on the PC to confirm that the hotspot was still sending serial data to the display.
Currently I have no idea whether this board was an official Nextion or not. I didn’t buy it direct from ITead (my mistake), and instead bought it from an eBay vendor in China, via eBay, because the vendor offered free shipping.
The vendor claims it is an authentic Nextion, but offered $4 compensation, which I rejected because I’d rather give negative feedback on eBay and warn other potential buyers that these boards may not be genuine.
My advice to anyone who is thinking about attaching a Nextion to their PiStar hotspot, is to buy direct from ITead, even though its likely to cost $10 more (about 30% more) than from third party vendors, because you are guaranteed to get a genuine board, and are also likely to get support from ITead if you end up having the sorts of problems I’ve had.
Even if my board was not genuine, I still don’t understand why it failed.
What appears to have happened is that initially the serial Tx line probably stopped working, hence the Nextion editor would not connect to the display, but the display still seemed to work when I connected it to my hotspot, since PiStar only sends data to the display and does not expect a response from the display
Subsequently, I think the Rx line into the display probably also failed.
I’ve used STM32 microcontrollers a lot, and I’ve never had a problem before with the serial Tx and Rx lines, even if I connect them the wrong way around. So I find it surprising that the serial lines on this STM32F030 have failed one after the other.
I did not disconnect the serial Tx and Rx lines from the hotspot, when I removed and reconnected the 5v input wire, to the display, when I was uploading via micro SD card, but again I have never had a problem with other STM32’s with leaving input signals connected when the MCU is not being powered.
However perhaps the STM32F030 used on these nextion’s is not very robust, and leaving the serial wires connected when I power cycled the display was enough to damage them.
Now that I’m left with a “bricked” display, I’m going to try to connect to the 5 pads on the back of the PCB, which I presume are the SWD debugger / programmer connections, but I’m going to need to work out which pads are which connections, because the Nextion is not open source and there is no documentation about what these pads are connected to.
Hopefully I’ll be able to use the screen for something, but for the moment its going into my junk box 😉