PSX Development

Displaying Text

The begining

I started my experiments by trying to display text. All of the examples I found were for Yaroze or something similar that we don't have access to in the lab (but I found the libs on some of the sites if you want them for your use). I found one example that was written in assembly. The only problem with this one was that it had an external file (which was included in the program at compile time) that it used for the font graphic data, and I could not get file access working so as to read in the file at runtime in a C program, since I know of no way to link a binary file with a C program at compile time. So, I wrote a short program that converted the FONT.BIN that came with the assembly program into a .h file that I could include in a C program. The resulting file is fontdata.h.

Porting the assembly

Cleaning up the assembly

How printing text works

• include "fontdata.h";
• include the printGPU, p2gpucommand, and WaitGPU functions and the SPR_X define in your program
• call loadfont() after initializing the GPU
• call printGPU("text", x, y, color) to display text

The printGPU function steps through each of the characters in the string, finds the appropriate texture coordinates for the character, and draws 2 8x8 sprites to the output coordinates in order to copy the 8x16 character graphic.

Displaying Arbitrary Sprites

	typedef struct {
		PsxUInt8 r,g,b,code;
		PsxUInt16 x,y;
		PsxUInt8 u,v; PsxUInt16 clut;
	} SPRITE;

• 0x74 - 8x8 sprite
• 0x7c - 16x16 sprite

Defining the texture page

  |1f-18|17-0b|0a |09 |08 07|06 05|04|03 02 01 00|
  |0xe1 |     |dfe|dtd|tp   |abr  |ty|tx         |

tx       0-f      X*64  texture page x coord
ty       0        0     texture page y coord
         1        256
abr      0        0.5xB+0.5 xF  Semi transparency mode
         1        1.0xB+1.0 xF
         2        1.0xB-1.0 xF
         3        1.0xB+0.25xF
tp       0        4bit CLUT
         1        8bit CLUT
         2        15bit direct
dtd      0  Ditter off
         1  Ditter on
dfe      0  Draw to display area prohibited
         1  Draw to display area allowed

void setDrawMode(PsxUInt16 tx, PsxUInt16 ty, PsxUInt8 abr, PsxUInt8 tp, PsxUInt8 dtd, PsxUInt8 dfe) {
	PsxUInt32 command;
	if (ty!=0) {
		ty = 1;
	}
	tx = tx >> 6; // Divide by 64
	command = (0xe1 << 0x18) |
		(dfe << 0x0a) |
		(dtd << 9) |
		(tp << 7) |
		(abr << 5) |
		(ty << 4) |
		tx;
	GPU_cw(command);
}

Displaying GPU status

Developing in the MSVC++ IDE

1. Download and unzip the Dos/Win32 GNU PSX development environment, and do the same for FPSE. Both of these and and example project are included in this .zip file : msvcpsx.zip. The example project file assumes it is operating out of E:\PSX, FPSE is in E:\PSX\FPSE, and it runs printGPU_sprite by default.
2. Create a new Utility Project. These allow you to define your own build scripts, like using GNU's compilers instead of MS's. Consequentially, you can use this same method to compile *any* type of code, like Java or Perl for example.
3. Add a new or existing C/C++ file, and right click on the file in the file explorer, choose Settings. Under the Custom Build tab, you define the commands and output. Enter the string "$(InputName).exe" as the output (without quotes), and I use this script for my commands (cut and paste it, after modifying the directory/drives).
4. Under Project Settings, Debug tab set the Executable for Debug Session to the full path to FPSE.EXE, the Working Directory to the directory FPSE is in, and the Program Arguments to a full or relative path to the executable you want to run (the one generated in the above script - same name as your .c file, but as a .exe).

What you need to do is up the memory that CMD.EXE or COMMAND.COM uses for evironment, or set these variables globally.

If you are using Windows NT, 2K, 2K3, or XP, you can set these environment variables under Control Panel | System | Advanced | Environment Variables, or something like that.

Otherwise, you want to up the memory for command.com. In Win9x, you can put something like this in your autoexec.bat file:

SET COMSPEC=C:\COMMAND.COM /E:8192

Or (probably the easiest way out of all of these), make one batch file that has all of these commands you want to run like this.

And then in MSVC++ have the script run this:

C:\COMMAND.COM /E:8192 /C WORKER.BAT $(InputName)

You may need to replace "C:\command.com" with "C:\cmd.exe" or "c:\windows\system32\cmd.exe"

What I learned

• Everything I ever wanted to know about CLUTs, except, perhaps, why mine wasn't working.
• BabelFish knows Japanese better than I do, but knowing a little Japanese helped dig through some pages.
• Although very low-level gpu.txt has lots of good information, and makes sense after reading it a few times, and consuming enough Mt. Dew. Similarily, I'd assume gte.txt, spu.txt, system.txt, and cdinfo.txt (all by the same group, I believe) are just as good.