Jeff and Jason Tranter's XGameStation Home Page

The XGameStation Micro Edition (XGS ME) is a video game console platform developed by André Lamothe to teach computer game hardware and software design. My son and I purchased a unit in February 2006 and are having a blast learning how to program it.

This page lists some XGS resources that we've found useful and describes some of our current projects.


XGS Development on Linux

The official development tools included with the XGS ME are for the Windows platform only. As a Linux developer, I want to use my platform of choice. There are some solutions for Linux users:

Gputils

The GNU PIC Utilities or gputils project has developed a number of tools including an assembler and linker that supports a number of processors including the SX series. The assembler syntax is different from the Ubicom/Scenix assembler that ships with the XGS, so porting existing programs is a challenge.

Gsxprog

Gsxprog is a utility to program devices using the Parallax SX-Key or SX-Blitz. Many XGS users have purchased the optional SX-Key programmer. This program has not been maintained for some time but it works with the most recent model of SX-Key that comes with the XGS.

Sxide and Sxemu

An IDE for Linux as well as a simulator are under development and available from Rainer Blessing's Site.

Wine

The Wine Project allows running many Windows programs under Linux. Wine is (finally) approaching its 1.0 release after many years in alpha testing. I have found that most of the Windows and DOS-based tools for the XGS will work well under Wine. In particular, the Scenix assembler shipped on the CD works flawlessly.

The one exception is the XGS Micro Studio IDE. I spent an evening playing with it under Wine and the first hurdle is that it uses the winio.vxd driver which Wine does not support. One solution would be to write a native Linux replacement for the winio.dll. I actually tried this, creating a a stub library with the required functions, building it and linking it with Wine. I then encountered another crash in Wine that seemed unrelated to the winio library. I may revisit it some day.

The SX-Key IDE works quite well under Wine. All editing and debug features work. It occasionally loses contact with the SX-Key but I haven't used it under Windows so that may be normal.

SX Programming API

I was able to port the SX Programming API to Linux in one evening. This API allows you to read, write, and program the XGS using the parallel port. I've also written a simple command line utility to program the XGS with a hex file. You can get the source code
here.


General XGS Links

Here are some useful XGS web sites:
  1. Official XGameStation site
  2. Ubicom web page for the SX processors
  3. Parallax web page for SX chips and tools
  4. Eric's Ubicom Microcontroller Page

Our Current XGS Projects

I have a pair of original Atari joysticks which I bought around 1981 for my first computer. I've put new connectors on them, cleaned the contacts and they work great with the XGS. We also have a Commodore 1702 monitor which makes a great retro display.

XGS Cheat Sheet

I've created a brief cheat sheet which summarizes the common XGS registers, I/O port assignments, and programming info.

Colour Demo

Here is a simple demo application that lists all of the colors available. It uses the XGS Tile Engine. A screen shot is shown below.


Tank Battle

This is my first attempt at a simple tile-based game, Tank Battle. The source code is
here. It is still pretty rough around the edges but the basic game play is there. It is a two player game that requires two joysticks.

I wrote a similar game around 1982 on my first computer, an Ohio Scientific Superboard which used a 6502 processor. I still have the code on cassette tape somewhere (binary of course, it was assembled into machine code by hand).


Vole

The source code is here. You'll want to read the instructions below before playing the game.

On a small planet in a faraway galaxy there lives a peaceful race known as the Voles. They have lived in harmony for 10,000 years until a giant meteor smashed into their beloved planet. Helpless to save themselves from extinction, they depend on you, a brave astronaut, to deliver them to safety. After your long journey to the planet Volia, you set out to evacuate the last survivors. An entire race depends on you!

Scientists of Earth have supplied you with Telepads which can be used to teleport any survivors you find to the mother ship. You must roll the voles into the telepads (or push the telepads under the voles) to rescue them. Here are your instructions:

  1. There are five (5) levels you must complete in order to save the voles from extinction.
  2. Each level has a certain number of voles to rescue. You must rescue them ALL!!
  3. You can restart a level by pressing Fire.
Voles:
Voles are easily recognized by their round, fat bodies. These peaceful creatures cannot move on their own, but they can be rolled on the ground and into telepads. Be careful though, they can easily get stuck in corners or against walls. Voles are also very heavy, and can only be pushed one at a time.
Blocks:
Many of the buildings and structures on Volia were destroyed when the meteor struck. As a result, blocks lie on each level. These large, green blocks are quite heavy, but can still be pushed around. They can also be pushed into the telepads (to dispose of them.) Since blocks weigh a lot, they can only be pushed one at a time.
Walls:
Some structures on Volia cannot be moved. These metal frames act as impassable barriers. You will have to find a way around these objects, for even you telepad cannot chew through these!
Telepads:
The telepads were dropped onto Volia to make it easier to evacuate voles from the planet. These mobile teleporters serve another purpose: They can be used to demolish blocks to find hard-to-reach voles. To rescue a vole, push the telepad into the vole or the vole into the telepad. The same applies to demolishing blocks. Keep in mind that Walls cannot be demolished. Also, be careful not to get your telepad stuck in a corner!
You:
You (the white stick figure) will start somewhere on each level. You can move up, down, left or right by using the joystick. You can push blocks, voles, and telepads by moving directly into them. Take care not to trap yourself between blocks, or you and all of Volia will suffer the same fate!

Each level has several ways to beat. They start off easy, and get more challenging as time goes on. If you get stuck somewhere, or make a mistake, just press the Fire button to restart at the beginning of that level. Once you complete all five levels, you win!

Good luck!!


Nintendo Zapper

I've made some progress interfacing the Nintendo light gun with the XGameStation. Here are more details.

XGS Programming Tips

The SX52 processor on the XGS can be somewhat challenging to program, not just because of its limited RAM and ROM but it has various quirks. Here are some random tips I've picked up that may help others who use this chip.

Get an SX-Key. As an XGS owner you can get it at a special price from Nurve Networks. It will save you a lot of headaches when it comes to debugging and you can use it to reprogram the SX20 processor on the XGS or other SX chips you may want to use for hardware projects. Before you use it though, you should develop some software without it so you can experience the fun (!) of debugging programs without any debugging tools except your own wits.

Learn how the paged ROM and banked RAM works on the SX52 chip. Even after reading the data sheet and the various tutorials, it probably won't be until you write some real code that it starts to sink in how it works.

If having to generate low-level video timing scares you, start by using the tile engine. It's not hard to use and many games can be implemented using it. Then, later, you can read the source and understand how it works.

Make use of the XGameStation forums to discuss ideas and problems with other users and report your successes.

If you really get stumped during debugging, try hooking one or more LEDs (and current limiting resistors) to unused output ports and flash the LEDs to indicate things of interest in you code. If you have an oscilloscope you can use it to view output ports and get accurate timing information too. Using the sound chip is another possibility to help in debugging.

The most common programming errors, in my experience, are:

The Tile Engine by default uses colours with a colour reference of 14. If you want the other colours you can change it by setting the variable color_phase in Game_Update, e.g.

	mov color_phase, #COLOR_0 

You can often shorten your code by changing any instructions that add or subtract by one to use increment and decrement instructions and clearing instead of setting to zero, e.g.

Instead of:		Use:

add foo, #1		inc foo
sub foo, #1		dec foo
mov foo, #1		clr foo
These are shorter because the ones on the left are compound instructions. With the limited (4K words) available on the SX52, every instruction counts!

Here is a trick I used in my two player tank game to simplify the code. I store the per player variables in different banks. The logic operates on one player each frame, alternating frames. I use the same code for both players, but just switch the RAM bank for the appropriate player.

To protect your XGS from accidents like dropping metal objects on it and shorting it out or spilling drinks on it, make a plastic cover cover for it. Cut a square piece of clear plexiglass the same size as the XGS circuit board, drill holes in each corner, and mount it using metal standoffs. Make sure the standoffs are long enough so that you can still reach the power and programming switches. If you use the expansion connector or any of the other headers, you need to cut openings for them. [I wanted to install my XGS inside the case of a Nintendo NES but my son won't let me take it apart.]


Jeff Tranter, <tranter@pobox.com>
1