Troubleshooing first attempt at repo cart

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neeneko
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Troubleshooing first attempt at repo cart

Post by neeneko » Sun Feb 07, 2021 5:45 pm

I am not sure if this should go in here or the hardware forum, but since I am a complete newbie to all of this, I figure this is the place to start. I've watched various tutorials and read as many posts as I could find, but I seem to be missing something so I am hoping someone might have some troubleshooting advice.

I am attempting to build my first repo cart and thus am still pretty new to all the tools and part. For my test case I am using an NTFS Test Cart ROM since I would like a basic testing tool. The ROM itself runs fine in fceux. It loads into famiROM fine and identifies it as an NROM with 16KB (128kb) PRG, 8KB (64kb) CHR. I tell it to target 27C128 for both and it splits fine.

For burning I am using one of those tl866II Plus burners and Xgpro software. It identifies the chips as STMicro M27128As, so no weird 24v requirements. They pass the blank check, they claim to write, everything seems fine.

For the actual hardware I am using a muramasa NROM board, v1.02. Using the cap it came with, but instead of soldering the chips directly to the board I connected sockets instead. I've done this for both the CHR/PRG and lockout chip. Given how many times I've tried playing with Xgpro's settings in the hopes of finding some mistake, I'm really glad I went that direction.

I have been testing it using a top loader. When I power it up I get a red screen (same as if I boot with no cart), but I also get the first few notes of the test sequence.

The only idea I have (left) is that, according to the spec sheet, the M27128As only has 200ns access time.. but to be honest I am not all that confident about what the chips actually _are_ since I also have some other eproms that claim to be ST M27C256B chips (45ns access time), but the programmers claims they are coming back with the ID for Fairchild FM27C256. Either way, those chips produce the same results.

Can anyone spot something I might have missed, or suggest another direction to try? Any help would be appreciated.

neeneko
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Re: Troubleshooing first attempt at repo cart

Post by neeneko » Mon Feb 08, 2021 6:51 pm

ok! answering my own question, and incase anyone else runs into a similar roadblock, maybe this will be helpful.

So, to try to figure out what went wrong, I made use of one of those INLretro Dumper-Programmers. This was also a new tool to me, so I tested it by dumping a known good NROM game I had (Burger Time) and testing that in an emulator, so that worked.

I then pulled the repo cart in and dumped it, which looked good. However, loading that into fceux again produced a red screen. I did notice though that during the dump inlretro reported 'vertical mirroring sensed', which did not what match what famirom reported. On the board I had bridged the centre and left (H) pad for mirroring, but I went back, switched it to centre and right (V) pad, and it came up just fine.

So hopefully that will help someone down the road.

It makes me wonder though, how do people generally handle testing rewritable memory like this? a DIP socket + EEPROMs just barely went into a top loader without a shell, and even just using a partial shell they ended up hitting part of the loader in the toaster version. Is there some bit of hardware for getting the connectors a little further out, or do people just gut a NES and attach it to some plywood?

lidnariq
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Re: Troubleshooing first attempt at repo cart

Post by lidnariq » Mon Feb 08, 2021 7:09 pm

You can get super-low profile sockets like these: https://www.advanced.com/products/peel- ... 54mm-pitch
that go into the holes on the existing PCB.

tepples
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Re: Troubleshooing first attempt at repo cart

Post by tepples » Mon Feb 08, 2021 7:14 pm

Nintendo's terminology used on NROM and discrete logic cartridge PCBs is based on how the two unique nametables are arranged next to each other. V pad means vertical arrangement of nametables. This terminology is opposite of the mirroring terminology that the early emulation scene adopted.

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Quietust
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Re: Troubleshooing first attempt at repo cart

Post by Quietust » Tue Feb 09, 2021 6:39 am

tepples wrote:
Mon Feb 08, 2021 7:14 pm
Nintendo's terminology used on NROM and discrete logic cartridge PCBs is based on how the two unique nametables are arranged next to each other. V pad means vertical arrangement of nametables. This terminology is opposite of the mirroring terminology that the early emulation scene adopted.
I was going to mention this, but neeneko claimed to be using a muramasa NROM board, v1.02. Unfortunately, that site doesn't appear to indicate whether the H/V solder pad labels follow Nintendo's definition (as described above) or the .NES format's definition (which is the exact opposite).
Quietust, QMT Productions
P.S. If you don't get this note, let me know and I'll write you another.

neeneko
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Re: Troubleshooing first attempt at repo cart

Post by neeneko » Tue Feb 09, 2021 8:17 am

lidnariq wrote:
Mon Feb 08, 2021 7:09 pm
You can get super-low profile sockets like these: https://www.advanced.com/products/peel- ... 54mm-pitch
that go into the holes on the existing PCB.
Oh that is good to know. Kinda in the 'option overload' stage when poking through digikey/jamco/etc, so missing a lot of solutions.

neeneko
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Re: Troubleshooing first attempt at repo cart

Post by neeneko » Tue Feb 09, 2021 8:23 am

tepples wrote:
Mon Feb 08, 2021 7:14 pm
Nintendo's terminology used on NROM and discrete logic cartridge PCBs is based on how the two unique nametables are arranged next to each other. V pad means vertical arrangement of nametables. This terminology is opposite of the mirroring terminology that the early emulation scene adopted.
Ah, that would explain it. Bit of a recurring story in the tech field....

Hrm. So while I am not planning on doing this, I am curious.. if I were to go the donor cart route, assuming NROM, if I had a ROM that FamiROM reports as vertical, looking through the NES Cart Database, would the donar cart need to be vertical, or horizontally mirrored?

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Quietust
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Re: Troubleshooing first attempt at repo cart

Post by Quietust » Tue Feb 09, 2021 8:27 am

neeneko wrote:
Tue Feb 09, 2021 8:23 am
tepples wrote:
Mon Feb 08, 2021 7:14 pm
Nintendo's terminology used on NROM and discrete logic cartridge PCBs is based on how the two unique nametables are arranged next to each other. V pad means vertical arrangement of nametables. This terminology is opposite of the mirroring terminology that the early emulation scene adopted.
Ah, that would explain it. Bit of a recurring story in the tech field....

Hrm. So while I am not planning on doing this, I am curious.. if I were to go the donor cart route, assuming NROM, if I had a ROM that FamiROM reports as vertical, looking through the NES Cart Database, would the donar cart need to be vertical, or horizontally mirrored?
If you are using a genuine [NES/HVC]-NROM-[128/256] donor board with a .NES file marked as "Vertical mirroring", then you should connect the "H" solder pads to indicate that it uses Horizontal scrolling - as noted above, the terminology used by NES emulators is the opposite of what Nintendo used.
Quietust, QMT Productions
P.S. If you don't get this note, let me know and I'll write you another.

neeneko
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Re: Troubleshooing first attempt at repo cart

Post by neeneko » Tue Feb 09, 2021 8:29 am

Quietust wrote:
Tue Feb 09, 2021 8:27 am
If you are using a genuine [NES/HVC]-NROM-[128/256] donor board with a .NES file marked as "Vertical mirroring", then you should connect the "H" solder pads to indicate that it uses Horizontal scrolling - as noted above, the terminology used by NES emulators is the opposite of what Nintendo used.
ok! This is making sense. Thanks!

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