Ok, what did I do wrong here?

AB_Positive · Post by **AB_Positive** » Thu Oct 30, 2008 7:06 pm

Trying to turn a Zelda cart into Zelda: Outlands. Following the advice on here I ended up with this:

... if this is right, I may have messed up cutting the traces, but I'm pretty sure I got that right. If the wiring isn't right, someone mind telling me what I did wrong?

BMF54123 · Post by **BMF54123** » Thu Oct 30, 2008 8:37 pm

You forgot to tell us exactly what problem you're having...

AB_Positive · Post by **AB_Positive** » Fri Oct 31, 2008 7:46 am

Lack of booting - heh, sorry.

I cut traces, filled the eprom by double-writing, and soldered the new chip on following the instructions for a SNROM board.

SNROM (mapper 1):
Bend up pins 1, 2, 24, 30 and 31 (or cut tracks 2, 24 and 30)
Solder pin 2 to hole 24 (A16)
Solder pin 24 to GND (OE)
Solder pin 30 to hole 1 (A17)

... I get a grey screen on booting. Did I mess up the soldering or is the soldering correct and I should check the traces?

Bregalad · Post by **Bregalad** » Fri Oct 31, 2008 9:25 am

Use a ohm-meter to check how good you cuted traces and how good your solder connexions are. When cuting traces, it's common that it's in fact not cut and there's still a connexion.

AB_Positive · Post by **AB_Positive** » Fri Oct 31, 2008 9:51 am

Bregalad wrote:Use a ohm-meter to check how good you cuted traces and how good your solder connexions are. When cuting traces, it's common that it's in fact not cut and there's still a connexion.

... crap. I need more equipment.

Does the soldering look right though? I don't know if I really soldered "pin x to hole y"

If it looks good then I know it's the traces. I'll find an ohm-meter from a friend and get it going proper.

Bregalad · Post by **Bregalad** » Fri Oct 31, 2008 9:58 am

Just in case a "beep-meter" (aka an ohm meter that just made a beep when the connexion is close to 0 ohm) is enough.

AB_Positive · Post by **AB_Positive** » Sat Nov 01, 2008 7:44 am

okies... I just tried making a Mapper 0 cart and it soooo did not work. Mapper 0 (using a US Popeye cart) would work one would think so... maybe I'm doing something wrong with either the eprom burner (checked the voltage, that's good) or can I be using chips that are too large?

It's penguin wars which is a 32 kb prg and a 8 kb chr. Maybe I didn't split them right with Midnight Commander? What do people recommend for rom splitting and whatnot.

I'm working on learning assembly but I'd also like to know I can make my own carts too... the soldering was done well with no traces crossed. Any help would be appreciated, I boot to a blank grey screen.

Bregalad · Post by **Bregalad** » Sat Nov 01, 2008 7:48 am

32kb PRG is 27C256 and 8kb CHR is 27C64.
If you use 28Cxxx EEPROMs instead of 27Cxxx EPROMs rewiring is needed, but if you use EPROMs no rewiring is needed at all so it should be hard to fail to do that devcart.
Use an hex editor if you need to split files, but my EPROM programmer can do it internally so I don't even to do that personally (but yeah I bought the expensive version).

AB_Positive · Post by **AB_Positive** » Sat Nov 01, 2008 8:16 am

oh...

you HAVE to use the proper 27Cxxx size per file? I thought you could just keep writing through to the end with garbage data or double write and it'd be good. :/

crap, so I should get a lot of multiple size chips now? :/

Bregalad · Post by **Bregalad** » Sat Nov 01, 2008 8:25 am

I thought you could just keep writing through to the end with garbage data or double write and it'd be good. :/

Writing garbage will likely not work, unless you are sure that higher adress pins are LOW. Double write will be OK in all cases, so no, you don't need to get multiple size chips. However, the wiring changes as new adress pins are added, be sure to check for that.

AB_Positive · Post by **AB_Positive** » Sat Nov 01, 2008 8:51 am

Bregalad, do you have IM or can I PM you?

Something tells me I'm just missing some small thing here to get things right.

Bregalad · Post by **Bregalad** » Sat Nov 01, 2008 9:45 am

Well, go ahead and ask it.

AB_Positive · Post by **AB_Positive** » Sun Nov 02, 2008 9:34 am

Well what confuses me is that with a mapper 0 board, and two 27C256 chips... why wouldn't the game work - as mapper 0 boards supposedly need no wiring or modification.

I did however forget that 256 bytes = 32 kb... and I did a double write on the PRG chip (Penguin Wars = 32 kb prg, 8 kb chr). Should I have not double written the prg?

Could I have static shocked the chips to kill them? I'm just confused on what step I messed up on. Splitting the rom correctly looks like the biggest possibility but as an IT professional I like to know all possible errors so I can eliminate possibilities.

Bregalad · Post by **Bregalad** » Sun Nov 02, 2008 10:06 am

- as mapper 0 boards supposedly need no wiring or modification.

True as long as you use the exact same chips as the board is supposed to accept.
NROM-128 accept a 27C128 for PRG and 27C64 for CHR, NROM-256 accept 27C256 for PRG and 27C64 for CHR.
It's of course possible to use a 27C256 for CHR and tie the highest adress lines (A13, A14) to ground. You'll have to cut traces and add wires to do that, it should be pretty simple if you look diagrams for both chips and compare them.

AB_Positive · Post by **AB_Positive** » Sun Nov 02, 2008 11:27 am

Ohhhhhhhhhh.

Well... let me try that then, I'm coming with a decent knowledge of soldering but none with microchips - is there a section on nesdev or... anywhere where one can learn about microchip logic and whatnot?

Thank you SO much for all the help, btw Bregalad, I appreciate it.

-Alli