Can i acess a serial LCD through an actual serial port (DB9) via Arduino

I am trying to use my UNO to control a serial LCD that is hooked up to teh back of my computer through the DB9 serial connection. is this possible.

I haven't had any success connecting to my Matrix Orbital Serial LCD's via hooking them right into Arduino. I know my displays work via RS232 and a serial cable hooked to the back of my PC because they all work perfectly using LCDC software to drive them. Yes i soldered the jumpers after that to convert it to TTL serial.

This should be possible i hope? talking to the display through Arduino via USB then into the pc then out the serial and into the display?

any help would be appreciated. along with a very basic confirmed general "hello world" sketch would be awesome.

Could you give a link to that display ? (just copy the url in a post).

You should be able to connect it to an Arduino.
Sometimes a serial port is able to switch between 'real' RS232 and TTL-level serial data, but sometimes also the signal has to be inverted. The 'real' RS232 higher voltage signal uses inverted levels.

It should even be possible that the Arduino acts as if it is a display.


lk202-25-v 20x2 LCD 1U HMI with RS232, TTL,USB


I have all these matrix orbital serial displays. some can handle ttl with jumpers they are all rs-232 capable.

I am basically wondering if instead of opening the serial monitor you can just open another port that the display is using and export to that. No physical connection of the display directly to the arduino and i would be using non ttl levels this way.

What do you want ?
Using the LCDC software works, but what is the next step ?
Do you want serial ports on your PC to connect a few displays ? or do you want usb plugs to connect to the displays ? Or perhaps a single Arduino that controls a whole bunch of them ?

If you want a simple serial terminal, you could try the Q Serial Terminal,
That way you don't have to start the Arduino IDE.

I thought i explained it but ill try again, I have a serial lcd display 5 of them actually. I have a serial connector on the back of my computer. I dont have a serial connector on the back of the arduino. I want to use the arduino to write things on the serial LCD as its hooked up to my computer. Why mainly right now because i cant get the damn things hooked up to the arduino itself.

so basically i want to know if the arduino is capable of sending the serial data through the IDE and istead of printing it on my computer screen in the serial monitor it just sends it to the serial lcd hooked up to the serial port on my computer.

I know the displays work plugged into the back of my pc but soldering jumpers etc just havent worked out as of yet hooking it through the arduino. So i want to use what i know works and plus its more convenient if ti works this way for learning debugging etc. because it sucks not knowing if the code is wrong or the thing isn't wired up correctly i can eliminate one of the two.

anyway yeah to the last guy asking what i want to do its actually all summed up in the one sentence title for this thread but i went ahead adn wrote out a few paragraphs as i havent had much success on this forum communicating i guess.

i found this excerpt from the arduino cookbook

Your Arduino sketch can use the serial port to indirectly access (usually via a proxy program written in a language like Processing) all the resources (memory, screen, keyboard, mouse, network connectivity, etc.) that your computer has. Your computer can also use the serial link to interact with sensors or other devices connected to Arduino.

It says i can gain all the resources my pc has all i want to do is send data out of the serial connector on my pc to my LCD so i dont have to solder and unsolder a ton of jumpers just to learn a few things. plus if the lcd goes bad i need to connect it that way to reset it there is soldering 4 more sets of jumpers to get it back to plug into the arduino etc.etc. i hope it makes sense.

So you want to connect the displays to the Arduino board ?

Which Arduino board do you have ?
I would like to use the normal serial connection (via the usb) for uploading the sketch and for the serial monitor of the Arduino IDE.

You need (a few) extra serial ports.
The Arduino Mega has 3 extra serial ports.
The Arduino Leonardo has 1 extra serial ports.
The Arduino Uno has no extra serial ports.

The SoftwareSerial library is included in the Arduino software.

You can use it to create more serial ports. So you still will be able to connect a few displays to the Arduino Uno for example.

Next step: connect the display to the Arduino.
If you could make the serial communication TTL level, that would make things a lot easier. Normally connect RX to TX and TX to RX. But sometimes the signal is inverted.
The SoftwareSerial has a (undocumented) feature for inverted serial data.

If you want to connect the higher voltage 'real' RS232 signal to the Arduino, you need a RS232 converter board. Most of them have a MAX232 or MAX2323 chip.

You won't have any trouble with inverted serial data with those converter boards, but they still could have the label "RX" for RX or TX and "TX" could be TX or RX. So you still have to try and see what works.

Or ... Do you you want to control the displays with an Arduino, while the displays are connected to the PC ?

Could you make a drawing of what you want. I still don't understand it.

Or ... Do you you want to control the displays with an Arduino, while the displays are connected to the PC ?

Yes this is what i want. I have an uno and i want to use the arduino to control the displays while they are still hooked up to my pc.

So it goes like this ARDUINO USB--->to my pc---> then to serial port on my pc--->LCD

Sorry it took a while XD , I was thinking what the Arduino could do, but you want to run a program on the PC.

It would require a program on the computer that communicates with the Arduino via a serial connection (the virtual serial port of the Arduino board) and with the displays also via a serial connection.

Are you familiar with creating software for a PC ? It is possible with Java, Python, C++ and many more.
The best thing to do is to find an example program that uses the serial port.
Try a few links in the Communication section of the Playground:

For example using a serial port in Delphi, Delphi tutorial: Bi-directional serial comms- dt4q
The Windows PowerShell is able to use the serial port,