Display Hookup  - Page 1
Forum section: electronics / beginners

author: vidarr
author_rank: Frequent Contributor
timestamp: October 05, 2018, 01:26:52 pm
content: I have a 3.5 Nextion display that has some empty pads. One of them looks like it could be for a micro-usb (was included loose with the display new). I look at the circuit and it looks like it very well could be. Can someone else please take a look. I am new at this, so surely there are much smarter folks than me around.Attached is the back of the display. The J4 pads are at the bottom. Notice the circuit goes by the battery location, thru some switches, capacitors, resistors, timer? Maybe for charging the battery? Then some lines look maybe go to the processor chip? If a better pic is needed, let me know.Thank you!Vidarr

author: janoc
author_rank: Super Contributor
timestamp: October 05, 2018, 01:37:38 pm
content: That cannot be a micro USB. Micro USB connector has 5 small signal pads (+D, -D, Vbus, GND and ID signals) and 4 (or more) mechanical pads around it.Like this (look from the bottom):https://media.rs-online.com/t_large/F0435706-01.jpgThat J4 footprint looks like some sort of power connector - notice that one pin is on the top copper pour, likely ground, and the other one goes to the D6 diode (below the U7 chip), most likely a reverse polarity protection. And the circuitry is certainly not a charger, the button cells are not rechargeable (in fact, they will likely explode/burst if you try to charge them!). The battery holder is there as a backup for the real time clock in the STM32F103 microcontroller in the center.But why are you speculating about what the connectors are for like this? They are certainly documented in the Nextion documentation, no? These smart LCDs generally use a normal serial port (UART) to communicate.See here:https://nextion.itead.cc/resources/datasheets/And this is maybe what the micro USB connector that you have found included in the box was meant for:https://nextion.itead.cc/wp-content/uploads/2017/09/Nextion_Power_Supply_Test_Board_05.pngI.e. to connect the display to a phone charger as a 5V power supply in order to test it.

author: vidarr
author_rank: Frequent Contributor
timestamp: October 05, 2018, 02:18:59 pm
content: OK, so it is some kind of power and not any usb. Thanks.I already used the included usb for power like it said in the docs to quickly test it. But, I have a breadboard with another power source so it is not really needed.Yes, they sell uart adapters like this:https://www.amazon.com/RobotDyn-Serial-Converter-adapter-CH340G/dp/B072637KDKI was hoping to send data to and from the device without using an adapter (I live in Brazil and shipping takes almost 6-8 months). Right now, I have to use a microsd card back and forth to the computer, which is ridiculous.There is also, on the side, some pads for some on-board programming I think?Maybe do something *kind of like* this:http://fab.cba.mit.edu/content/archive/projects/fabisp/Thanks,Vidarredit: I don't know if I make sense. Translate the technical is hard so I try to make it short, but it seems not right. When I read what I wrote above, it is not exactly what I want to say.Maybe I say to make sense:Need to read/write to display without transferring data with microsd card, or buying a uart/usb adapter. Is there some connections I can make to the circuit board to do this? There was no documentation coming with the display. Nothing on Nextion site to explain this. Contacted Nextion - they said closed and will not discuss.

author: vidarr
author_rank: Frequent Contributor
timestamp: October 06, 2018, 01:01:06 pm
content: Can someone please help me? I think I started this post wrong I got too stuck on the J4 question when it really wasn't my question.I need help to do this. If I wrote wrong in English I try to explain better. I just need help.Thank you.

author: bob225
author_rank: Frequent Contributor
timestamp: October 06, 2018, 01:45:05 pm
content: Have you downloaded there editor ?https://nextion.itead.cc/resources/download/nextion-editor/you connect to the display with a usb - ttl adapter or you can program it via sd card - you may be able to program it via arduinoTBH im not familiar with these displays as I use 4d system displays with there own ide

author: janoc
author_rank: Super Contributor
timestamp: October 06, 2018, 06:04:53 pm
content: Quote from: vidarr on October 06, 2018, 01:01:06 pmI am afraid that unless you buy a serial to USB adapter somewhere (that should be possible to buy locally even in Brazil, it is a very cheap and generic item used for a lot of industrial stuff too) or you use something like an Arduino to talk to the LCD, you aren't going to get anywhere.Depending on which Arduino you have you could even use the USB to serial converter on the Arduino board to talk to the display.The microcontroller on the board does have build-in USB interface but if the PCB is not designed to use it and the firmware isn't written for it it won't help you. There is nothing on that board that can talk directly to a PC.

author: vidarr
author_rank: Frequent Contributor
timestamp: October 06, 2018, 08:20:30 pm
content: OK. Thanks. I have an ESP32 dev board and a Mega, but they are already in use and will be pain to take all apart for this. It would be nice to just plug this into the computer with usb, like everything else.There might be an adapter here locally, but this is the north of Barzil, which is like Afrika, so it will be difficult to find and is going to cost 10x more than it does everywhere else.Do you think this one would work?http://electronics-diy.com/electronic_schematic.php?id=1006I see so many adapters I don't know the right one for this display. Before I go and order one that won't be here until April of next year, I try to find here for sale and also investigate making it.Thank you very much!

author: admiralk
author_rank: Regular Contributor
timestamp: October 07, 2018, 12:30:10 am
content: When you say talk to the display, I assume you mean program. In that case, I do not think your esp or arduino will be of much help for that. What you need, instead of using a card, is something likethis. A search on ebay, using "USB to TTL", will bring up several, some under $1. The same search other places will give you similar results. What you need is +5V, GND, RX, and TX pins opposite the USB connector.I have one like the one I linked and use it for arduino pro mini also.

author: janoc
author_rank: Super Contributor
timestamp: October 07, 2018, 10:01:45 am
content: Quote from: vidarr on October 06, 2018, 08:20:30 pmNO!You must not use an RS232 adapter! That will reliably destroy your board because it uses +12/-12V signalling!Your board expects 5V TTL levels - if you want to use that schematics, you will have to remove the MAX3243 level converter chip and only use the TXD and RXD lines from the CP2102 chip.These USB to TTL adapters are often sold as an "FTDI cable" (after the chip used on them) and similar. You need something like this:https://www.sparkfun.com/products/9718(the connector you will need to adapt, that's normal).Or one of these:https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20181007020439&SearchText=usb+to+uart+adapter

author: bob225
author_rank: Frequent Contributor
timestamp: October 07, 2018, 11:37:47 am
content: a quick google brings uphttps://www.smartprojectsbrasil.com.br/https://produto.mercadolivre.com.br/MLB-1102508393-modulo-conversor-usb-serial-uart-ttl-cp2102-win10-_JM