Robot Minefield C Port

After typing in the BASIC version of Robot Minefield, then porting it to Assembly, I decided to round things out by doing a C version as well. The C version was the fastest to port. I learned a lot doing the assembly version, and had a blast. The assembly was the most fun, but the most frustrating to write. My assembly foo just isn’t very strong at this point. Thinking in assembly still takes a while, but worse is not knowing all those pesky mnemonics!

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Robot Minefield Day 4

It is now day 4 of my Robot Minefield conversion to assembly. Last night was my first night I dreamed in assembly. I remember working on some problem, and assembly was involved. You know you have your head in the game when you dream about it. So far so good. I have the minefield randomly populating with mines and robots, and randomly placing the human somewhere on the field. Steve Bjork was kind enough to provide a random number generator in assembly, which was very easy to adapt. You can run the human around the minefield, and will die if you touch a mine or a robot. I just started working on the robot movement AI. You can view my initial post.

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Robot Minefield

Robot Minefield is a BASIC game I typed in from Tim Hartnell’s Giant Book Of Computer Games book. Neat game, and a simple enough game I’m using it as an exercise to write it in assembly. The game is a little like Rogue in that the computer doesn’t move until you do. But what’s most interesting about this game, is that it is a remake of a game called Robots and mines on the Commodore PET, and was one of the games that inspired the arcade shooter Robotron 2084.

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Bouncy Ball NG Progress report 5 Submitted iOS and Apple TV apps!

Progress to report on Bouncy Ball NG. iOS and Apple TV versions have been submitted today! Only took 12 builds. Had to kill off one bug, fix an issue with the splash screen on the iPad, but coolest of all was the new music.

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Bouncy Ball NG Announcement

November 27, 2017: Announcement
December 6, 2017: Progress report 1
December 31, 2017: Progress report 2 Apple TV
January 17, 2018: Progress report 3 the home stretch!
January 24, 2018: Progress report 4 signing the certs!
January 29, 2018: Progress report 5 Submitted to the app store!

I really had an itch to play Bouncy Ball, the Color Computer game I wrote back in 2016. I also needed to learn SpriteKit for iOS and macOS. So I put the two needs together and created Bouncy Ball NextGen for iPad, iPhone and Mac. Everything from the original is intact, only getting an update to the UI, level flow, and sounds.

When playing it on the Coco, I always thought the game worked really well using a joystick. Now on the iPad, touching the left and right side of the screen to make it scroll is a perfect replacement. It just feels right, especially with the buttery smooth scrolling.

I wanted to keep you in the game longer, and not break the action. So progression from level to level, and death no longer requires user input, and just jumps right back into the game.

You can check out my promo video below.

November 27, 2017

Basic Interpreter With Shared Variables

I expanded the BASIC script interpreter in to include an example of how you can share variables between your program and the script. For example, you can set a counter in your program, pass that value to the script, and have the script update the value, and then use the new value in your program. Note that since the make file is for Qt, I suggest you compile with g++ *.cpp -o basicscript.

The example ConsoleBasic class now shares two variables with the script, in addition to the CLS command we added in the previous post. An integer variable counter and a string in name$ are now read and modified in the sharedvariable.b sample script.

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Basic interpreter with custom command

I expanded the BASIC script interpreter in to include an example of how you can extend the interpreter and add your own commands to it. Sorry about the Makefile depending on Qt. I’ll create a generic Makefile next version I release.

I created a ConsoleBasic object, then added the cls command. You can see I add it in the constructor, then in execAddonCommand I check the token that is passed in to figure out what command I should execute, which in this case can only be one command, then clear the screen via ANSI escape codes.

Next example will show how to make your C++ variables available to BASIC.

class ConsoleBasic : public SmallBasic
    int m_cls;
    ConsoleBasic(const char* pszFilename)
        : SmallBasic(pszFilename),m_cls(0)
        m_cls = addCommand("cls");

    bool execAddonCommand(const int tok)
        if(tok == m_cls)
        return true;

Basic Interpreter for Embedded scripts

I had a few people interested in my BASIC interpreter that I was using as an embedded script interpreter. I had started using it in my MUD but pulled it out and made a stand alone example. It still needs a little cleanup and i still need to create an example of how to add more commands to it. See You can run the script with “basicscript hello.b“. hello.b uses a few commands and shows how you can use labels instead of line numbers. Line numbers are supported as well. Don’t be too hard on the code, I wrote it back in 2001!

6809 CPU Emulator project started

CpuEmulator is a CPU emulator project that aims to emulate a CPU (the 6809 to start with), it’s registers, and system memory. It will allow you to monitor registers, flags and memory as you step through code. Having done SharpiEmu for the Sharp PC–1360 Pocket Computer, the concept seems pretty simple. The 6809 has a number of addressing modes, and different opcodes for the same mnemonic. So I’m expecting it to be somewhat more of a challenge.

Initial version will emulate the CPU, memory, and text video mode.


  • Emulate 6809 instructions
  • Emulate 32×16 & 80×24 text modes
  • Emulate the Coco3’s MMU
  • 4K all the way up to 512KB memory options
  • Debugger that steps through code, shows current state of registers, selected memory block, and source code from a listing file.
  • Break points. They are remembered between runs.
  • Memory watcher. When memory at a certain addresses are modified, a breakpoint is triggered so you can see what modified it.

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CxxTest for unit testing C++ programs

I just discovered CxxTest, and just had to mention it. Fantastic unit test framework for C++ programs. To brush up on my C++ coding, I decided to write a simple 6809 CPU emulator, with the goal of being able to plug-in other CPU’s. This project really lends itself to the idea of unit tests. It’s very easy to test each part of the emulator, and check the results after an instruction has run.

After reading @noel_llopis‘s article Exploring the C++ Unit Testing Framework Jungle I figured I would check out CppUnit first, since I had seen it mentioned it was the standard on, or at least widely used. Not sure how that is possible, given the weak documentation and complicated setup. The docs never once tell you what to include and what to link against. 30 minutes later I decided to move onto CxxTest. Glad I did as CxxTest was very simple, and I had unit tests running within 5 minutes. The true mark of a well setup project. My emulator processed it’s first instruction today, LDX #$1234. And the unit tests were right there to validate the results.

Bouncy Ball 2 Progress Report #1

Bouncy Ball 2 Progress Report 1. First things first. We need to get the Coco 3 into it’s high resolution graphics mode, then display a little something. To start out small, I decided to create a program that sets the video mode, uses the MMU to map in the video memory, then clears the screen. That part was easy, although understanding the MMU was a little whacky.

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Bouncy Ball 2 Announcement

I’m happy to announce that Bouncy Ball 2 development has started! Design is underway, and the sound system already sounds awesome. We have been able to make the Orchestra 90 sound mad. It’s using full stereo sound, mixing 4 channels, and uses hardly any CPU. We have a lot to learn about the Coco 3. Join us every week or two on the BB2 development blog to watch our progress. We are Lee, Simon, and Paul.