I'm just now learning to use an Arduino and currently know very little. I'm working my way through the basics in the educational documents at the moment.
I didn't really have a plan for what to do with this device when I bought it, I just got it out of a desire to learn. I've been trying to think of a project to ultimately turn the atmega2560 into though and landed on a long term goal of building it into a word processor.
Please note, I do not want this to be anything too fancy. I just want to create a system that exclusively types text documents and can save them in a .txt file format. I still have a lot of things to figure out here including finding the best display and keyboard interface for this, and coming up with a way to save these text documents to another device for transfer from one computer to another.
Before I can get to any of that, I'm trying to figure out if this is even possible to begin with. I know from studying old 8-bit computers like the Sinclair and Commodore computers that 8KB of RAM simply isn't a lot and can easily be filled when typing documents. This has lead me to wonder if the RAM can be expanded, as if it cannot then I don't believe there's much sense in even trying to go forward with that project and I'll need to think about something else.
I searched around for a few minutes but didn't find anything specific. One search result that didn't specify which board was being used said that you could add up to 64KB, and there was another link where someone was experimenting with adding 8MB using some other hardware that's not intended for use with one of these devices. Which left me unsure.
From what I've read about old 8bit computers, having 64KB of RAM would make this viable and be enough for me to go ahead with trying to figure out how to make it work. Though a bit more would be nice.
My hope in the end is this can be a really compact battery powered terminal for typing. Probably look into mounting the whole thing onto a keyboard.
Mega may not be the best choice. There are many more modern Arduino compatible board which are smaller, have far more ram, and run on 3.3V, making them much better suited to battery power.
Yes, the Mega has a classic (8085...) External Memory Interface for up to 60KB. Static RAM requires an additional 8 bit address latch, while dynamic RAM deserves permanent refresh in code.