Had a big breakthrough yesterday with our Super Nintendo Snesram project. Got
for the first time a commercial game running. This was quite a hard one.
Spend a great amount of time debugging the memory uploads routines. I had to
add CRC checks to both sides of the hardware. An AVR hosted CRC memory check
and SNES hosted CRC check, showed us that our addressing was done
correctly. But we found out that no commercial game ran on our hardware. Why
that ??? More testing showed that we got a lot of memory corruption while
starting a game. First we thought that the bus driver switching ( which was
quite lazy implemented) caused the memory corruptions. Fixing that help a
little, we could boot Super Mario World. But that would crash right after the
start. Finally we found out that we shouldn’t map the WR line of the cartridge
to our sram. We always thought the snes uses an unique address space for the
rom and save game ram mapping. This might be true for the cpu address space but
not for the cartridge address space. So the games constantly wrote to save game
ram and destroyed the actual rom content….Fixing that worked out perfectly.
Right now we support up to 4mbit games. But We don’t have any save gave support
at all. Also HI ROM support isn’t tested yet.
The good thing is, now that we have our poc working we can move on to build an
actual pcb. Our main focus will be on homebrew stuff, so running all kinds of
commercial game is not our first target. This implies some hardware design
decision. We want to go for software usb for the bulk rom upload, and another
ftdi based usb for the cpu debugging or even for an control and user
interface. Like a little remote login shell to upload roms, peek and poke
memory…name it. If we have the board running with usb i see a lot of
features coming up. I am not sure if we go for an sd card slot, which in my
views is only interesting for gamers.
Also i have to admit that our approach, using an cpu and a static memory
addressing mode is limited. The way how Scott is
doing this gives him a lot more options to handle the black magic snes rom
layouts. Also he will have the option to synthesize DSP and FX chips onto his
fpga. So we might see him playing super mario kart on his board 🙂
But i also see an advantage in our design i guess if we make pcb kits they will be
suitable to be build by an average hobbyist geek.
Checkout the new logic analyser
Bus Driver Hotfix
Super Mario World running
The magic setup
We have been working the last 4 Weekends on a cool side project – we built a DIY Super Nintendo development hardware. As a SNES Programmer or SNES Nerd you always want to run your code on the orignal hardware. But this is only possible using old backup stations from the 90ies like the Super Wild Card or Game Doctor. But all these tools lack cool features like SD Card support, USB connection or real time debugging. I own an old Super Wild Card and its a pain in the ass. I can’t get the parallel port connection working and so i have to use the builtin floppy drive 🙂 There are newer projects around, but either not working or not really cool.
So we decided to build our own hardware. Today we got our proof of concept working. Its based on a STK500 setup using a ATmega16 (Ja.. I fried the ATmega32 while setting the fuses..). Attached is a SD Card and a home cooked memory bus driver for one 512k SRAM Chip.
Both the ATmega and the SNES memorybus are connected to this SRAM via busdrivers. The ATmega does the housekeeping and manages the access to the RAM. To save IOpins on the ATmega side, we use shiftregisters and counter to set the adress. On the SNES side its connected to a Snes Multi Cartridge Adapter. One slot holds an orginal game, so we can use the lockout chip from there and solder the data and address from the other slot to our memory interface.
Now we are able to upload a 2Mbit SNES rom. A mario sprite on flashing background. We load this rom image from the SD Card and write it to the attached SRAM. When this is done we switch the busdriver and connect it to the SNES memory bus. Today we got the demo working.
See the video and pics.
We did like 3 other proof of conecpts before to get this working.
Watch the Video on vimeo to get HD and see the console output
Right now we are planing the features for version 0.1. Its mainly to get a good hardware design
the cool software features are planed for version 0.2
- ATmega 644
- 4mb SRAM
- Address Counter
- Address SREG
- LO/HI Rom support
- Lockout Chip
- Save game SRAM
- SD Card Support
- Software USB
- USB Upload Client
- Software Mode Switch
- Remote Reset
The Project is hosted at Assembla.com
And the poc code is here
I had so much fun finding out how good the Snes9x GX Emulator for the Wii is. I never really got into the Wii hacking scene yet, just keept a little and h following the exploiting status of the wii. So when the Homebrew Channel came out, i installed it. But never really did something useful with it. But this weekend i installed Snes9x and it really rocked. Super performance, no framedrops or broken sound. And the GFX looks really crisp. Nothing compared to the last exprience i had when i hooked a Nintendo Jr. to my flatscreen tv. it looked really really crap. Dont get me started NTSC, composite signal and a tv software scaler..uh..really crap, unplayable. But the Emulator stuff looks really good on the big screen.
After testing Mario Kart i got pissed off the Wii Controllers. You are supposed to use them in the same manner as in Wii Mario Kart. Steer with Up and Down button and accel with the  Button. But no R and L buttons. Without them Mario Kart is no fun. After a quick internet research i found a project to connect and orginal Super Nintendo controller via the Gamecube connectors to the Wii. Its a little more complicated than a simple piggy tail, since the protocol used by the Gamecube and Super Nintendo are totally different.The Gamecube uses a more complex protocol so that you need a microcontroller to do the conversion.
Yesterday was DIY sunday, soa friend and me threw this thing together. And it works really good. My friend got so hooked, so he is planing to make some more of the controllers and put them on ebay.