visual artifacts in repro cart

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gmoothart
Posts: 4
Joined: Tue Dec 28, 2021 4:57 pm

visual artifacts in repro cart

Post by gmoothart »

Hi,
I just created my first repro cart (using the components and instructions from https://mousebitelabs.com/2020/09/11/ne ... ustom-pcb/). I used Micro Mages as my first attempt, and much to my surprise, it mostly worked! But there are a couple of issues I would like some help with.

The first is that the title screen doesn't display correctly. Visually it looks like some layers are shown/hidden improperly (screenshot attached). It's a minor problem, but when I play the ROM on an emulator it works fine.

The second issue is that after I play the game for some time (maybe 20-30 minutes) visual artifacts start to appear - short horizontal sections of the screen that flicker with what looks like random other sprites like letters/numbers. If I continue to play, I get more and more of these artifacts. Could this be caused by a bad solder connection on one of the pins? Any ideas about how I might fix it?

TIA,
Gabe
Attachments
PXL_20211229_001536370.MP.jpg
FrankWDoom
Posts: 260
Joined: Mon Jan 23, 2012 11:27 pm

Re: visual artifacts in repro cart

Post by FrankWDoom »

what mapper is the game? can you post a pic of your board? offhand i would guess mirroring might be wrong
poorstudenthobbyist
Posts: 252
Joined: Fri Jun 24, 2016 4:20 pm

Re: visual artifacts in repro cart

Post by poorstudenthobbyist »

Hello! (I am also Bucket Mouse of mousebitelabs.com)

This is an NROM game, but the mirroring you have is set wrong, I verified on my own test cart. FamiROM does report it as Horizontal - but that means soldering the middle pad to the "V" setting. I mention that in the guide but I don't blame you for missing it haha. It's confusing, but I wanted to keep the function the same as the OEM carts. I will consider adding a note on newer revs to make it clearer!

Here's an explanation on the wiki about it

As for your long term issue, that's a bit stranger. I haven't encountered that myself, it's possible it's related to your console instead of the board. But a picture of the board would certainly help though, as Frank mentioned!
gmoothart
Posts: 4
Joined: Tue Dec 28, 2021 4:57 pm

Re: visual artifacts in repro cart

Post by gmoothart »

Micro Mages is mapper 0.

I was about to say that I was pretty sure the mirroring was right, but in taking pictures of the board I noticed that I had actually neglected to solder the mirroring pad at all (as well as one differentiating chr ram/rom).

If that's the problem then I'm surprised it isn't even more broken than it is. I'll solder those pads and report back.

Gabe
Attachments
PXL_20211229_044924806.jpg
PXL_20211229_044910940.jpg
gmoothart
Posts: 4
Joined: Tue Dec 28, 2021 4:57 pm

Re: visual artifacts in repro cart

Post by gmoothart »

I soldered the "ROM" pads and "H" for the mirroring. But I just read poorstudenthobbyist's reply and realized I should use "V".

Anyway doing the above did fix problem #2. Let me switch to "V" and try that.

Gabe
Last edited by gmoothart on Tue Dec 28, 2021 11:25 pm, edited 2 times in total.
poorstudenthobbyist
Posts: 252
Joined: Fri Jun 24, 2016 4:20 pm

Re: visual artifacts in repro cart

Post by poorstudenthobbyist »

You should def solder the CHR pads to "ROM" as well, if they're left floating, all sort of weird unpredictable problems can happen. That should fix it up for you

Edit: oh, you mentioned you did that haha.
Let me know if the mirroring swap doesn't do the trick!
gmoothart
Posts: 4
Joined: Tue Dec 28, 2021 4:57 pm

Re: visual artifacts in repro cart

Post by gmoothart »

That fixed it, the intro screen works now and a few in-game artifacts are gone.

I did have the pads soldered in a test board with standoffs; but I forgot to do it in the board where I soldered the chips in.

And I actually did read poorstudenthobbyist 's note about H/V on the board being "flipped" but I didn't quite understand. Since I knew this was a vertical scroller I figured "flipped" meant I should select H.

Anyway, thanks for the help!
Gabe
Fiskbit
Posts: 891
Joined: Sat Nov 18, 2017 9:15 pm

Re: visual artifacts in repro cart

Post by Fiskbit »

There's some unfortunate terminology confusion here where Nintendo used what we call 'arrangement' while the emulation community chose 'mirroring', which have opposite meanings. For example, if you want to scroll horizontally, the two unique nametables are placed horizontally and duplicated vertically, with arrangement referring to where the unique tables are placed and mirroring referring to where they're duplicated. Nintendo's PCBs use H and V with the arrangement meaning, while most resources you find in the emulation community use mirroring and thus need to be 'flipped'.

The bad horizontal sections you were seeing earlier were likely because some lines were left floating, and so how they're interpreted by the PPU will depend on analog behaviors and potentially change over time.
poorstudenthobbyist
Posts: 252
Joined: Fri Jun 24, 2016 4:20 pm

Re: visual artifacts in repro cart

Post by poorstudenthobbyist »

Next rev of all NES boards with mirroring control via solder pads will include a note to make it clearer :)
attachment.PNG
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