#455 - Ford Guy - Tue Jan 07, 2003 8:25 pm
This is my first post here, so hi everyone! Does anyone know if there are any schematics for simple general purpose I/O cartridges with maybe some flash and ram also? I am thinking of something along the lines of the Xport device, but with inexpensive MCUs controlling the interfacing for addressing, code fetch, and memory mapping to I/O lines. JTAG or i2c ports could provide a quick upload of new I/O characteristics.
I'm long on theory but short on practice (I'm CS, not EE), so any pointers to resources would be great. I would love to use my GBA to provide "brains" for all kinds of uses. Thanks
#462 - ampz - Tue Jan 07, 2003 10:18 pm
A MCU is waay too slow to handle adress decoding. It has to be done with logic.
Of course, the mega-size FPGA they stuck in the xport is a major overkill.
If you only need a few gpio's then the GBA comm port might be useful to you. I has three or four gpio's.
If you want to build a cart with built in gpio yourself then you might wanna check out my schematics for a basic GBA cart:
www.hh.se/stud/d99tibr
Just add adress decoding and a latch or buffer and you have your I/O's.
The cheap AMD flash memory in the schematics can be replaced by a intel strataflash if you need more space, or if you want it to be compatible with standard linker software.
Another way is to extend the GPIO's on the comm port.
A way to get 10 more inputs would be to open up the GBA and abuse the keypad inputs, but I guess you don't want to do that.
#471 - Ford Guy - Wed Jan 08, 2003 12:41 am
You are right, a microcontroller is too slow. I just looked at some of the bus timings, and at best I could only execute 5 MCU instructructions, which would be meaningless.
Your design looks just like what I'm after... Thanks for setting me straight before I went too far up the MCU alley! :)
#472 - ampz - Wed Jan 08, 2003 12:58 am
74ac191 IC's can be a bit hard to find, they are not that common, but www.digikey.com has them. (they also have several suitable flash memories)
#537 - Lord Graga - Wed Jan 08, 2003 3:07 pm
To make a bigger cart (128 mbit) with save-support, what components do i need then?
What do i need for a small cart with ~512 KB and save support?
#573 - ampz - Wed Jan 08, 2003 9:35 pm
The schematic is obviously valid for all flash sizes. I thought that much was obvious..
Basic save support is easy, just use a part of the main flash memory, no extra components required.
Of course, such savegame support is not compatible with Nintendo savegame hardware, but that's not a problem since we don't do piracy.
#736 - nintendodev - Fri Jan 10, 2003 1:43 am
What book do you reccommend, so I can follow that GBA Cart schematic?
thanks!
#768 - ampz - Fri Jan 10, 2003 1:55 pm
A good book on digital electronics and computer architecture (digital busses). I can't recommend anyone in particular.
A college/university course on the subject might be the best way to learn..