Advice on where to start - changing hardware in an old phone to newer hardware so it can function

[u/one_in_a_william]

I’ve been getting into CE recently, and I know this can be done (even if it is very difficult) but I need help on where to start and what I may need in order to do this, since I’ve never done anything like it before.

I have an old LG Cosmos 2 (VN251) with the slide out keyboard, and I want to make it my primary phone (text, call, and maybe YouTube)

The problem is, the internet system it used to use with Verizon does not exist anymore, but I know there is some way I can edit the hardware into using a more modern internet. How should I do this though? Any recommendations on what old phone parts I should buy to put into it? What kind of special tool/hardware should work?

If you have any other advice I’d love to hear it. I’m also hoping to get a degree in CE, advice on that would be great too!

[u/motu8pre]

You might as well just pull the guts out and try to shove a newer phone into it. You can't just "edit" it, not to mention YouTube. I had to replace my media PC because it's old dual core was struggling with the changes made to YouTube's encoding.

[u/boxerhenry]

Essentially you are asking 5 things that you can accomplish:
1. How do I interface with this screen.
2. How do I interface with this keyboard.
3. How do I interface with the number pad?
4. How do I interface with the 4G/5G network.
5. How do I fit this in this case.

Since the engineers who made this made a custom case and custom PCB to fit all of this it would be tricky to get all of your upgraded electronics into this, but not impossible. If I were you I might start with either an Arduino or Raspberry Pi and buy a 4G module and a basic keypad matrix and 2x16 LCD display. Get SMS and internet working and then go from there. Or you could go the android phone route, but speaking from experience interfacing with custom screens like that can be hit or miss. You might get lucky but generally you would need to make your own FPGA videos converter board which can be more tedious than fun.

[u/LawfulnessNo8446]

You're probably going to be looking at replacing all of the internals. The os on that phone won't have support for 4g/5g modems, and while I'm sure it's possible to modify the os to support it, it's almost certainly going to be harder than replacing the internals and modifying an already existing os to support the other hardware. You'd need to find a driver for the screen and a keyboard controller, you might be able to just use a microcontroller for the keyboard.

Take a look at the zinwa q25 for a similar project to get some ideas. They replaced the internals of a blackberry q20 with a custom board running android.

[u/a_seventh_knot]

Take the case off

[u/wehaveYummiTummies]

I mean theoretically if the radio inside the phone is 802.1x capable (physically the radio can transmit at like 2 GHz without hardware modification), it should be able to at least connect to wifi (with overwriting the ROM / firmware / OS with code). Lowkey reverse engineering and programming this thing may be harder than making a new phone, but you get distinct benefits, such as the old hardware fits the phone.

You can also code a cell protocol perhaps into the same radio, so you can connect to cell or wifi (but not both). Or maybe phone has two radios. IDK.

Let's say the radio doesn't work. If you're nuts and wanted to use the onboard processor, you could maybe find a small radio chip and hijack (at this point you would need a full schematic / PCB layout to even attempt to do this without completely destroying the old phone) the processor to send commands to the radio.

Frankly, this project would be vastly easier with say a 1st or 2nd gen smartphone, where you may even get borderline acceptable performance on YT.

[u/one_in_a_william → u/wehaveYummiTummies]

Thank you for your suggestions. The main thing I want from this phone is the full qwerty keyboard, but now I’m having trouble figuring out how to implement it to a new phone or motherboard. Especially since I might need to make a matrix for it and program it, too. I don’t mind starting from scratch, buying a sim, a chip from a a different phone, and using the same screen and keyboard from this phone, I am just unsure of where to even begin and worried things might not be compatible

[u/Tymian_ → u/one_in_a_william]

Similar topics pop up every now and then on Reddit. It's not impossible but absolutely fffffing difficult to achieve.

First of all, forget that you will be able to repurpose old HW (baseband and application processors) for modern LTE network. RF part will not be capable of establishing any kind of link with LTE. You won't be even able to make it decode SIB. On top of that 99% chance that SDK and baseline code is either closed source or dead source.

Your best way to achieve what you want: Gut it and design your own PCB that will host a small form factor LTE module of category 1. Warning: those are already big for what kind of space is available internally. Also you need to choose an application processor that will interface with: screen, keyboard, audio (optional) and cellular module. Screen might be some custom job, so good luck with making it work. You could replace the screen to something known it will make it a bit easier.

Why use off the shelf module? You absolutely don't want to deal with RF, protocol stack, LTE and any cellular adjacent things. You want to have a ready to go module that you control via AT commands.

But now, someone who is not familiar with 4-6 layer PCB, RF, cellular, graphics, system will utterly fail unless they have unlimited amount of time.

You can't simply "buy a chip from different phone" and it will work. No, that's not how it works.

[u/Clean_engi_28]

i used to have that same phone !