Emulation Multi-platform builder scripts for GBA emulators

[patters]

The 0x8002 was me just following the documentation. I believe the FPGA is truncating (Reducing to multiple of 4 in this case) the value to 0x8000 anyway. It doesn't a seem to hurt the EZIV.

Does 0x8000 definitely work on EZ-Omega?

 

[hippy dave]

For good measure - here are the disassemblies of each of HVCA's flashcart reboot functions:

• flash_ez1.sub
• flash_ezfa.sub
• flash_fa.sub

Each of these routines has a consistent end section:

mov r0, #0
mov r1, #0x4000000
strh r0, [r1, #-6]     @ store half-word 0x0000 at address 0x3fffffa
mov r0, #0xfc          @ move word 0x000000fc into register r0
svc #0x10000           @ supervisor call 0x10000
svc #0                 @ supervisor call 0x00000

More known-good EZ-Flash reset code here:
https://github.com/EvilJagaGenius/jagoombacolor/blob/master/src/visoly.s

It also uses supervisor call 0x10000 followed by supervisor call 0x00000.

Post automatically merged: Apr 25, 2023

Ok, so here is my tweaking of the flash_ez1.sub disassembled source to create flash_ez4.sub:

# HVCA exit code for EZ-Flash IV / 3in1 / Omega
# by patters in 2023
#
# https://gbatemp.net/threads/multi-platform-builder-scripts-for-gba-emulators.611219/post-10138443

add   sb, pc, #0x48          @ sb = start of .BYTE definitions
ldm   sb, {r1, r2, r3, r4}
mov   r5, #0xd200
mov   r6, #0x1500
strh  r5, [r1]               @ 0x9fe0000 = 0xd200
strh  r6, [r2]               @ 0x8000000 = 0x1500
strh  r5, [r3]               @ 0x8020000 = 0xd200
strh  r6, [r4]               @ 0x8040000 = 0x1500
mov   r0, #0x8000
ldr   r1, [pc, #0x34]        @ 5th .BYTE
strh  r0, [r1]               @ 0x9880000 = 0x8000
mov   r0, #0x1500
ldr   r1, [pc, #0x2c]        @ 6th .BYTE
strh  r0, [r1]               @ 0x9fc0000 = 0x1500
mov   r0, #0
mov   r1, #0x4000000         @ 0x9fc0000 = 0x1500
strh  r0, [r1, #-6]          @ 0x3fffffa = 0x0000
mov   r0, #0xfc
svc   #0x10000
svc   #0
.BYTE 0x00, 0x00, 0xfe, 0x09
.BYTE 0x00, 0x00, 0x00, 0x08
.BYTE 0x00, 0x00, 0x02, 0x08
.BYTE 0x00, 0x00, 0x04, 0x08
.BYTE 0x00, 0x00, 0x88, 0x09
.BYTE 0x00, 0x00, 0xfc, 0x09

...which assembles into the 104 byte file which is attached to this post.
And it actually works on my EZ-Flash IV! I'm very pleased with that.

I think it ought to work on EZ-Flash 3in1 / Omega / Omega DE too. Please try it and let me know. You'll need to add the exit sub using my build script's -x command line option.

The final point of confusion is that if you select <EXIT Emulation> from the menu it only resets the emulator. You need to Hold L+R whilst in the menu to actually exit back to the flashcart menu (keep holding while the screen turns black). The clue to this was in the rather intriguing controls schematic in the HVCA readme.

Take note - all of this was made possible by Open Source. I know next to nothing about ARM ASM, and I'm not a software developer. If I can do this then so can you, with curiosity, logic, and patience.

Interesting discussion above, but all I can tell you so far is that this attachment definitely works on my Omega Many thanks!

 

[TechieSaru]

Does 0x8000 definitely work on EZ-Omega?

Just ran a quick test. It works fine.

Edit: I did another test and it turns out I was right about the truncation. It seems only values that are a multiple of 512 are used by SetRompage. Evidentally, their documentation was wrong.

 

[patters]

Great. I had already uploaded it with RomPage 0x8000, to match all the other examples.

 

[patters]

I did a bit of reverse engineering and added a builder script for ZXAdvance. It can extract the emulator gba binary from the exe file and it will read ZXA.INI for control schemes.
https://github.com/patters-match/gba-emu-compilation-builders/blob/main/zxadvance_compile.py

 

[CrashMidnick]

Thanks for your work ! Very useful