Jeff and Jason Tranter's XGameStation Home Page

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

XGS Development on Linux

Gputils

Gsxprog

Sxide and Sxemu

Wine

General XGS Links

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

XGS Cheat Sheet

Colour Demo

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

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

XGS Programming Tips

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:

• forgetting to set the right bank when using RAM
• putting subroutines in the upper half of a page
• jumping or branching across page boundaries
• forgetting the "#" sign when using immediate operands

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

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.]