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Homebrew AR/PSX blaster like project

Posted: June 6th, 2019, 9:56 am
by paulm
I've been trying to learn basic hardware stuff. For this project I am trying to create something like the PSX blaster. At the moment I have a breakout board and have been trying to attempt to bread board an EEPROM to it.

Not much luck so far as the retail AR carts seem to do some strange obfuscation trick of swapping some data line pins around. Therefore I need to reflash an EEPROM without the crazy pin swapping but I've yet to get that far.
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Re: Homebrew AR/PSX blaster like project

Posted: June 6th, 2019, 5:13 pm
by LameGuy64
Getting a EEPROM chip to work on the PS1's expansion port shouldn't be too difficult to do. Wiring up the address, data and chip select/output enable should work provided the EEPROM contains some code that the PS1 will execute.

The AR and even the Xplorer's design isn't really all that complicated actually. They usually have a bus tranceiver for communications and a PAL/GAL chip used to detect which chip activate based on the address the I/O operation is occurring with (ie. if read on address 0x0-0x1FFFF (0x1f000000-0x1f01FFFF on PSX side), select EEPROM chip. if write on 0x60008 (1F060008 on PSX side), select bus transceiver/comms hardware).

You can find more technical info about the AR/GS/Xplorer carts here: http://problemkaputt.de/psx-spx.htm#cheatdevices

Re: Homebrew AR/PSX blaster like project

Posted: June 7th, 2019, 4:48 am
by paulm
Is there a way with PSYQ to create an expansion rom header? or must it be hacked in manually/with a custom tool?

Re: Homebrew AR/PSX blaster like project

Posted: June 7th, 2019, 8:54 am
by Yagotzirck
Can you share some info about that breakout board(more specifically where you found it/how you built it)?
I've been searching for a PSX parallel port male connector for a while with pretty much your same goal in mind, but to no avail :shrug
Brutalizing an existing cartridge is out of the question, but having some spare parts of said connector for a reasonable price would be neat :)

Re: Homebrew AR/PSX blaster like project

Posted: June 7th, 2019, 5:07 pm
by Dedok179
Has anyone already parsed the firmware or the CD disk gameshark to pull out the functions that implemented cheat codes?

Re: Homebrew AR/PSX blaster like project

Posted: June 7th, 2019, 5:45 pm
by danhans42
I have also started looking at this, so if you want to compare notes it could speed things up. My expansion breakout board is nowhere near as pretty as your custom one. My idea is to add a header to break out the connector as well as an EEPROM.

I managed to remove the connector from an AR clone that was beyond repair. My first port of call was a 3.3v EEPROM as I have quite a few Am29LV040's kicking around. As LameGuy64 said, its fairly easy to get a EEPROM working on the parallel port and the comms are simple. Trimesh said he had the verilog from the orignal GAL/PAL and it was fairly simple.

The GAL/PAL also handles the switch function, so it maps the switch into the address space. Also, when looking at some of the xplorers, they are they are a little different as they also have 128k SRAM on board that I believe is mapped in the middle of the ROM space.

Re: Homebrew AR/PSX blaster like project

Posted: June 7th, 2019, 5:56 pm
by danhans42
paulm wrote:
June 7th, 2019, 4:48 am
Is there a way with PSYQ to create an expansion rom header? or must it be hacked in manually/with a custom tool?
Look at romprod by sicklebrick (on this forum), or Romboot here - https://www.sinistersoft.com/romboot or run rom by barog (although I think with latter you need a CD in the drive).

Re: Homebrew AR/PSX blaster like project

Posted: June 7th, 2019, 7:16 pm
by LameGuy64
ASMPSX and ARMIPS can be used to create expansion ROM programs complete with header data. I even have a cart based CD booter program made using GNU assembler (not recommended) though its quite crude.

You can find it right here: https://github.com/Lameguy64/PSn00bSDK/ ... es/cartrom

Re: Homebrew AR/PSX blaster like project

Posted: June 8th, 2019, 2:44 am
by paulm
Yagotzirck wrote:
June 7th, 2019, 8:54 am
Can you share some info about that breakout board(more specifically where you found it/how you built it)?
I've been searching for a PSX parallel port male connector for a while with pretty much your same goal in mind, but to no avail :shrug
Brutalizing an existing cartridge is out of the question, but having some spare parts of said connector for a reasonable price would be neat :)
I took the PSX blaster design and just broke it out to some pin headers and then sent it off to JLPCB. Then I desoldered a connector from a dead AR cart and put it into the new board with some pin headers.

danhans42 - yes I would be interested in working with you on this.

LameGuy64/danhans42 thanks I shall check that out. When I get my EEPROM flasher working I'll try to get a hello world booting.

Re: Homebrew AR/PSX blaster like project

Posted: June 10th, 2019, 6:02 pm
by danhans42
Cool.

First job for me is to get a DIP socket mounted and wired up and get the PSX working with it. I have 3.3v flash roms spare so that will eleviate the need for a voltage regulator on the cart.

I also want to add a header to my board so I can easily breadboard extra hardware to it - and start looking at the way the switch works as is mapped into memory and how that can recreated in modern hardware.

I have a USB programmer, as well as an old AR clone that has a ZIF socket mounted for my flashing needs.