Writing a “bare metal” operating system for Raspberry Pi 4 (Part 11)
Putting it all together
Frankly, I’m unlikely to write much documentation for this part. I’m also only providing a Clang Makefile for now. If you’re using gcc, have a go at putting your own Makefile together, referencing the previous parts.
This part simply builds on the work we’ve done so far, and delivers a new Breakout codebase with:
- Gameplay running in the foreground on the main CPU core 0
- Graphics updated in the background on CPU core 1
- Looped 8-bit music playing in the background on CPU core 2
- Bluetooth communications managed in the background on CPU core 3
I’ve taken the opportunity to organise the code a little better and so you’ll see some changes to the Makefile, and a new directory structure in place. Tidy codebase = tidy mind!
Important takeaway
As you read through this code, you’ll maybe notice that a very different style has emerged. Multi-processing adds a dimension of complexity when coding and requires a total mindset shift.
There’s a lot more signalling/semaphores, so the cores can be sure they’re doing the right thing at the right time.
You’re no longer “dry-running” a single, sequential thread. You’re having to spot the potential for bugs/unexpected behaviour from the interplay of four concurrent threads!
Good luck as you explore the code!
Progress video
Click to watch a quick video of the game in action.
https://user-images.githubusercontent.com/68182575/173157526-2b22f9b2-0f55-42a0-87e1-b8278930fefe.mp4
PS: Sorry for the bad audio quality - the game itself sounds great in real life, I promise!