RPi 3 using a 4.3" inch touch screen

It comes down to the datasheet for the LCD in question. After getting the electrical correct, the software driver would be the next challenge. No one answer here will predetermine success or failure.

Clem

In general: Raspberry pi has HDMI and "composite" out.

Your screen needs that as an input to be able to work. I bought a 'composite 4.3"  lcd screen' 20 years ago, and tried it on my pi. The quality is horrible. More modern stuff may be a bit better, but part of the ugliness comes from the composite "protocol" to transfer the video data.

4.3" screens usually do NOT work directly with HDMI. So you could get some sort of adapter. Those boards exist, but are usually bigger than the pi and the 4.3" screen. Not useful if you want to stay within a certain size.

That leaves getting the pi to speak the protocol of the 4.3" screen. There are lots of screens that can be controlled using a few GPIOs by a microcontroller like an arduino. The PI can of course do the same as the arduino.

The problem however is to get the driver for the raspberry pi. It is possible to write a driver that checks what should be on the screen periodically and then updates the screen accordingly. If you buy a 4.3" screen on Ebay suitable for raspberry pi, they will have written such a driver.

I've bough such a screen, and when I was ready to try it a few months later, it turned out that as a driver they had a kernel image with the driver included. This kernel was outdated and didn't support the recent versions of the raspberry pi. And illegally they did not want to provide the source to the driver.

So... If you manage to find a "4.3 inch screen for raspberry pi", be sure you check out how the software works before you buy.

EDIT: I checked out the market for what's available "NOW", and it is a bit better than before. Now you can get a 4.3" screen plus HDMI converter for $33. Not a touch screen though. You'd have to look a bit further for that....

You are right to be concerned about connections and protocols.

The 'Official' 7" touchscreen works as follows,

The 800 x 480 display connects via an adapter board which handles power and signal conversion. Only two connections to the Pi are required; power from the Pi’s GPIO port and a ribbon cable that connects to the DSI port present on all Raspberry Pi’s. Touchscreen drivers with support for 10-finger touch and an on-screen keyboard are available on the latest Raspbian OS for full functionality without a physical keyboard or mouse.

The DSI port is a special connector on the Raspberry Pi. Some other Raspberry Pi touchscreens work via pins on the GPIO header and very different protocols and drivers. If your project requires the use of the GPIO pins you may find such screens prevent the use of the pins you need.

I think you need to research touch displays that are designed to use the Raspberry Pi DSI socket. You cannot assume that it will be as easy to set them up as it is for the 'Official' display because the official displays have specific support from the latest versions of the Raspbian operating system. I suggest you get them from Raspberry Pi accessory dealers that give full documentary support for connecting screens and setting up the operating system for the specific display and touch screen system. Try to get close to the 800 x 480 screen resolution so that your project does not require major revision to work with a smaller screen.

Most generic touch displays don't use a DSI port connection. Note that the 7" display comes with a custom made adapter board to interface with DSI. Getting a generic display to work on a Raspberry Pi is a job for someone with extensive related software and hardware expertise.

You say

My team had been given a 4.3" screen with custom-made cover, as it'd been using by our seniors during the earlier stage of product development.

If it is not made to use the Raspberry Pi DSI socket, is not a touch screen or does not come with Raspberry Pi set-up documentation, I can't see what use it would be.

Thank you for your comment, you'd enlighten me on this issue.

So it seems that the Pi screen has an adapter board special designed to allow the screen to communicate under DSI, I will talk to the customer support and see what can we do with the project.

Thank you for the comments

So I think I would required to check the current drivers for alternatives screen to ensure they are supported before I choose them, am I right?

GPIO based screen... hmm, I guess we need to discuss onto this matter before deciding items to be included in the recommandation list

Anyway, thank you.

Thank you for the reply

So, what should I look for, in the datasheet of LCDs, to confirm the compatibility of the relative screen?

Software driver would be another issue we need to further research in parallel with solving this, I guess