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Writing a “bare metal” operating system for Raspberry Pi 4 (Part 12)

Porting the WordUp Graphics Toolkit

Back in the mid-1990s (when I was young!), programmers who wanted to build their own games didn’t have rich frameworks like Unity. Perhaps the closest we got was the WordUp Graphics Toolkit, which I came across on the Hot Sound & Vision CD-ROM - a BBS archive. If you have a moment, perhaps use Google to see what “bulletin board systems” were… nostaglia awaits!

Much like my very simple fb.c, the WGT provides a library of graphics routines which can be depended upon for reuse. This library, however, is much more fully-fledged than mine, and makes it easy to build sprite-based games (like Breakout, Space Invaders, Pacman etc.).

The directory structure

As I port the WGT to my OS (a.k.a. make it work on my OS), I am using the following directories:

Please note: I am neither a Node.js developer, nor a Swift developer, and so the controllers are purely samples that serve my purpose. They are not intended to be exemplars! I am very aware of the multitudinous problems with both…

Building

So… to build the first WGT sample simply type cp samples/wgt01.c . from the top-level directory, and then type make. When you boot with the generated kernel8.img you will see the screen go into 320x200 (VGA!) mode and draw a white line from corner to corner. If you do, the library is doing its stuff!

boot/boot.S changes

We’re still booting into a multicore environment (just in case we need it). There are a few significant changes to boot/boot.S though. They are:

Using the iOS BLE controller

To use the iOS BLE controller instead of the Node.JS controller, ensure that you have:

#define IOS_CONTROL

at the top of each of wgt/mouse.c and lib/bt.c. Without this #define, the code will be looking for the Node.JS controller (so remove these lines if that’s what you want!).

Work in progress!

There’s always more that can be done, but I do think this was a good exercise in exploring the joy of getting other people’s code to run on your own OS! It’s quite a thrill.

Do have a go at building some of the samples (hint: wgt20 and wgt60 are super fun!)…

I’m going to move on from here now so we can continue to make progress on the OS itself.

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