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Category: raspberry-pi

Raspbian vs Raspberry Pi OS

Posted on June 10, 2020June 2, 2020 by David

I’ve always referred to the version of Debian running on a Raspberry Pi as Raspbian and so it was until the recent 8 GB RAM Raspberry Pi was launched. But it turns out that Raspbian was an independent version of Debian created by people at raspbian.org. As they say “Note: Raspbian is not affiliated with the Raspberry Pi Foundation. Raspbian was created by a small, dedicated team of developers that are fans of the Raspberry Pi hardware, the educational goals of the Raspberry Pi Foundation and, of course, the Debian Project.”

From now on, it seems the correct name is Raspberry Pi OS and no longer Raspbian. The change was announced at the bottom of this Raspberry Pi Foundation blog post. This has something to do with the fact that Raspbian is mainly 32-bit while the Raspberry Pi OS is both 32-bit and 64-bit though the latter is still at beta. You can read more about the recent changes to Raspberry Pi OS on this blog entry.

Expanding my virtual hard disk

Posted on June 5, 2020May 30, 2020 by David

Most Linux development is done on Ubuntu running under Hyper-V on my Windows 10 PC. If you have lots of RAM (and I have a full 64 GB), it’s very convenient. I run Snagit on Windows and this makes it very easy to grab screenshots of the Ubuntu window.

I also have a “Raspberry-pi” running under Hyper-V. There’s a Raspbian desktop that you can download and run in Hyper-V, VirtualBox or VMWare though I’ve only done Hyper-V. Don’t forget when you are running a Raspberry Pi this way that its x86 based not ARM. That does affect the available software, so it doesn’t behave exactly like a real Pi though often close enough.

Today though I started getting low disk space from my virtual Ubuntu. That’s the problem with virtual machines. When you first setup a Virtual hard disk, you never know just how much disk space you will need.

There’s a terminal command that shows how much space you have left.

df -h --total

This produced this

david@david-Virtual-Machine:~$ df -h --total
Filesystem      Size  Used Avail Use% Mounted on
udev            942M     0  942M   0% /dev
tmpfs           193M  1.4M  192M   1% /run
/dev/sda1        11G  9.9G  603M  95% /
tmpfs           964M     0  964M   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           964M     0  964M   0% /sys/fs/cgroup
/dev/sda15      105M  3.6M  101M   4% /boot/efi
tmpfs           193M   16K  193M   1% /run/user/121
tmpfs           193M   24K  193M   1% /run/user/1000
total            14G  9.9G  4.1G  71% -

This was after I’d extended my virtual hard disk. You can see I now have 4.1 GB free.

The pretty picture is from a utility filelight. You install it in the usual way

sudo apt install filelight

Or if you prefer a more visual insight, install qdirstat.

sudo apt install qdirstat

This is like WinDirStat on Windows but qdirstat seems to run many times faster. It took a couple of seconds to produce this image below. WinDirStat would take 10-30 minutes.

So how did I expand my Hyper-V hard drive?

First you have to get rid of any checkpoints. Save your Hyper-V session if open then delete the checkpoint.

Right click on the checkpoint for the selected VM and click delete. This will take a minute or two and you’ll see it have a Merging status. You may need to shutdown the VM.

After that you can go into the settings and it will let you edit the virtual hard drive and change the size.

Raspberry Pi 4B with 8 GB RAM on sale

Posted on June 3, 2020June 3, 2020 by David

I won’t be buying one for the moment but I mention it for another reason. 4 GB is the maximum RAM that a 32-bit OS can use, and on the PI like on Windows it’s actually 3 GB. To be fair you can have two processes each with 3 GB on the 8 GB Pi.

The announcement did mention that a beta 64-bit Raspbian OS is available for download and it’s here. This article shows that the 64-bit Os they tested is faster on the Pi than 32-bit. This link to the DietPi forum tells you how to boot dietpi into 64-bit.

It’s to be hoped that 64-bit ARM development software will become available. Clang and gcc should be but I’m thinking of the code.headmelted.com version of Visual Studio Code.

As always if you are buying a Raspberry Pi 4B, I strongly suggest you get a case with a fan. They are not expensive and do make a difference. Despite running the Asteroids game, which is pretty intense, I have never got my 4B temperature above 51C. THat said I’ve ordered a touchscreen with a case for a 4B on the back and it doesn’t seem to take a fan. So it will be interesting to see what its like fanless. More on that when the touchscreen arrives.

Fixing an unbootable Raspberry Pi

Posted on May 19, 2020May 7, 2020 by David

Well to be fair, it was me that made it unbootable. I’d been reading this Wiki page on configuring the Pi. I’d told it to give the GPU almost a GB of RAM. The Pi is a 4 GB Pi 4B. I did it last night and so this morning, I found it not working at all well.

My first thoughts were I’d messed up the Operating system and so I took the SD card put it in a holder and booted up my old laptop which has Ubuntu 18.04 LTS on it. This page on switchdoc suggested I could do a repair with these commands.

First lsblk to view attached devices. There was a /dev/sdc2 . There was also a /dev/sdc1

Then

sudo fsck -fy /dev/sdc1

That gave information about the drive but not the disk. That took

sudo fsck -fy /dev/sdc2

That took a few seconds and listed information, but still my drive wouldn’t boot back in the Pi.

Then I remembered I’d changed the boot config.txt and it was back with the SD card in the laptop and rebooted that. It showed two devices on the desktop (no need to mount anything) and clicking boot gave me a directory listing of /boot. I edited config.txt and changed the GPU Mem value to 256MB.

That fixed it and my PI is now booting quite happily again. I am now going to make a backup copy! It wouldn’t the end of the world if I had made it permanently unbootable, I’d just burn the OS again. It’s just the time wasted and minor hassles copying files, downloading and reinstalling software. Best avoided if possible!

Success with gamepad mappings

Posted on May 15, 2020May 17, 2020 by David

SNES Gamepad — Image by Marco Sberveglieri from Pixabay

My ploy with running gamepad-tool on the Linux laptop worked and I was able to get the correct mappings to use in my game. Though weirdly it seems to have X and Y buttons mixed up as well as A and B.

In the end I hard-coded the mapping string and set it up with this code:

	if (SDL_GameControllerAddMapping("030000001008000001e5000010010000,NEXT SNES Controller2,platform:Linux,a:b2,b:b1,x:b3,y:b0,back:b8,start:b9,leftshoulder:b4,rightshoulder:b5,dpup:-a1,dpdown:+a1,dpleft:-a0,dpright:+a0")==-1){
		LogError("Unable to load gamepad mappings from gamepad.txt");
	}

Then in my ProcessEvents() function which handles I/O events, I added this code:

			case SDL_CONTROLLERBUTTONDOWN:
			if (event.cbutton.state== SDL_PRESSED){
				switch(event.cbutton.button){
					case SDL_CONTROLLER_BUTTON_A:
					    fireFlag =1;
					    break;
					case SDL_CONTROLLER_BUTTON_B:						
					    jumpFlag =1;
					    break;
					case SDL_CONTROLLER_BUTTON_X:
					    shieldFlag =1;
					    break;
					case SDL_CONTROLLER_BUTTON_Y:						
					    thrustFlag =1;
					    break;						
					case SDL_CONTROLLER_BUTTON_LEFTSHOULDER:
					    rotateFlag = 1;
					    break;
					case SDL_CONTROLLER_BUTTON_RIGHTSHOULDER:
					    rotateFlag= 2;				
					    break;
					}
				}

There’s similar code for the SDL_CONTROLLERBUTTONUP except it checks for the state = SDL_RELEASED and in the switch statement it sets each flag to 0. So inspite of the code, it’s the Y button that does shields and the X button does thrust, B button fires and A button does the hyper space jump.

More on Raspberry Pi Gamepad

Posted on May 14, 2020May 3, 2020 by David

Unfortunately there’s no gamepad-tool for the PI, but there is a program called jstest and in particular a visual one called jstest-gtk. That’s it on the left. You install it on any Linux system, including Raspbian on the Pi with the command

sudo apt install jstest-gtk

Then run it with a jstest-gtk command from a terminal.

It then detects your game pad and responds to button presses and joystick movements.

The weird thing is although my gamepad identifies it as a NEXT SNES but so far attempts to load that have not been successful in the Asteroids game. It loads but doesn’t seem to work and its not recognising the right shoulder button and has A and B buttons muddled up. Yet in jstest, it is clearly able to identify them.

Time I think to create a mapping under Linux with gamepadtool. Unfortunately it doesn’t work on the Hyper-V Ubuntu so it’s time to fetch my Linux laptop and try it on that.

My Orange Pi – self resurrected

Posted on May 12, 2020April 30, 2020 by David

Back in November 2018, I was in Nottingham and passed a stand at the Winter Fayre. It was offering a console with 18,000 games on it for about £70. I bought one and what I got was an Orange PI with a 16 GB SD Card (all but full) and two USB joypads.

The game software used the Retro-Pie software, but the games were a massively illegal collection of games (for about ten different consoles including CBM-64, SNES, ZX Spectrum) put together by the company that supplied these “consoles”. Amazingly I found four games on there that I had written back in the 80s in this collection.

It was a bit of an odd PI. Instead of powering up through the power slot, it came with a USB to 5V connector. Looking about on the web I found it is this model in a nice acrylic case. Anyway, after three months it stopped working and it was pushed in to a drawer where it remained until today. I tried it today and it came back to life, I suspect the mains-to-USB adaptor is broken but as I’ve a drawer full of them it’s not a problem.

The reason for mentioning this is not the Orange Pi, nor the games but the joypads. I had a look on the libSDL website and I hadn’t realised that there was quite extensive support built in to SDL. So my next task is to add game controller support for the asteroids game.

Developing for Raspberry Pi without one

Posted on May 10, 2020April 29, 2020 by David

Yes it is possible, as the screenshot shows. You can download a copy of Raspbian from Raspberry-pi. You can either download the .iso directly or save them a bit of bandwidth and do it via a file Torrent. It then takes about 15 minutes or so to install it. When you first run it, it will do an update.

It looks exactly like Raspbian on a PI but there are one or two little things to bear in mind. It’s 32-bit, the clipboard doesn’t seem to work and SSH by default is disabled. It’s real easy to enable it, just find Raspberry Pi Configuration. Click the Raspberry in a circle menu button at the top, then click Preferences and there it is on the menu that pops up. In the Interfaces tab, tick the Enabled checkbox for SSH.

I use the excellent WinSCP to connect to it. Conveniently the Pi will show you its ip address (or from a terminal run ifconfig and it will show you the ip address of eth0) and just put that in with username pi and your pi’s password which you should have changed when you set up Raspbian.

Finally you have to install Visual Studio Code and as usual, it’s not quite so easy. Most Linux distros these days are 64-bit and the official VS Code is only available for Debian in 64-bit and Raspbian is of course 32-bit. But there are community builds and it’s the same place that I got the ARM version from.

And here’s the result. A slightly sluggish (well it is under Hyper-V). I had to comment out the code that initialises the audio. Line 580 ish.

/*	int success=Mix_OpenAudio(22050, AUDIO_S16LSB, 2, 8192);
	if (success==-1 ) {
		LogError("InitSetup failed to init audio");
	}
	LoadSoundFiles();
*/

And here’s the results.

Slight change in direction – more C++ and Pi

Posted on April 27, 2020April 18, 2020 by David

As I said recently, writing about C and games probably isn’t enough to sustain this site, but if I extend it to include C++ and Raspberry Pi and still maintain the overall direction of writing about game development then that I think will do it.

So I’ve added a new page for C++. I’m currently working on the C++ version of Asteroids and making good progress.

I’m striving to write it in modern C++. To that end, the first entry in the C++ page is a link to a very long document: C++ Core Guidelines written by two luminaries of the C++ world Herb Sutter and Bjarne Stroustrup (creator of C++). You should definitely give it a read.

Interesting fact about the Raspberry PI. Did you know that in March 2020, they sold 640,000! That’s pretty amazing! And while that article says that AAA game playing isn’t something you can do on a Pi, we now know that you can run simple 2D arcade quality games on a Raspberry Pi 4.

Raspberry Pi 4 – Perfect for arcade quality games and development

Posted on April 26, 2020April 25, 2020 by David

I got my Pi 4 a week ago and have been doing experiments on it with my Asteroids game. If I disable the line of code that kills the player ship in the DestroyObject() function and just add a return after case tPlayer: and uncomment the code that adds Asteroids when you press A then I can have lots of asteroids on screen. Also set the MAXASTEROIDS #define to 128.

Then you get the likes of this screenshot which is a 1024 x 768 size window. It’s still running at 40 fps, there are 116 asteroids on screen, around 60-70 explosions and the Pi’s temperature is still a balmy 44.79 C. I’ve never got the Pi’s temperature (and it does have an internal 3.3V fan) to rise above 51 C.

But what’s also impressive is that with Visual Studio Code and Clang on the PI, I can compile the whole 2,200 lines of C on the PI in about a second. This makes the Pi very usable for developing games. And I say this as someone who is used to powerful Windows PCs for compiling code.

This is it running in debug mode; that’s all the numbers and wire frame bounding boxes around every moving object.

Further experimenting and removing the limitations (I used a While loop to limit it to 60 fps back before I had enabled the hardware video flyback). With that while removed and the hardware video flyback disabled, I was getting over 100 fps with 100 asteroids on screen at once. I pushed it up to 6,000 asteroids and the frame rate dropped to 10 fps. Given the amount of stuff that was colliding and blowing up, that’s still very good.