just so you know. I'm also having problems with my Nanoloop cart...

OK what I don't understand is why the ROM seriously glitches out after starting it but works fine after pressing B, which I've looked up to be the paste function. Is it trying to load preset data at startup and failing because it can't use save states on the nanoloop cartridge? Also, I think it's really interesting that the glitches are depending on the specific DMG I put the cartridge into. The green one does the charset cycling as described for the screenshot above, the grey and black ones both show the same different but static pattern. All of them work after pressing B. I will try this out with another black and a red one which I should both be getting soon.

The mGB ROM is actually only 32k, the upper 32k are empty. I don't know why it has been padded to 64k.
When nanoloop receives a ROM for A or B, it waits till 32k are received and then starts the ROM.

If mGB or any other ROM starts but shows strange behaviour, that most likely has nothing to do with the transfer. If the ROM starts at all, that means the full 32k were transferred and you also can assume that data were intact. If bytes were missed, it wouldn't start at all but hang at the nanoloop boot screen, waiting for 32k to complete. If bytes were corrupt, the ROM would probably crash immediately.

And yes, for unknown reasons, you first have to press B in mGB.

yes same here so it must be mGB. Also i noticed that when sending mGB to nanoloop1.6.3 the terminal shows it is sending 64 kb and the cart restart after the first 32 kb finished and there comes mGB.

I have the sneaking suspicion that you are right and the transfers that have totally failed were in fact caused by cellphone interference. However the "good" ones that still start up with a weird screen seem to be fully operational after pressing B once.

as far as I've read (from oliver himself, who makes nanoloop) the upper 32k of mGB should be empty and it should not be a problem. I'll give it a try though and see if it improves matters.

I think I found out what the problem is regarding mGB

The visual weirdness goes away when I press B once, and actually after that it works fine. I've thoroughly tested it just now, putting notes and cc messages on all 4 channels.
When I load a preset for a channel (if that's what pressing B on the preset option does), it will load garbage and the corresponding channel will fuck up its display just like on startup. pressing B outside the preset options seems to reset mGB to a good/default state. So I am assuming now that the garbage display has to do with mGB attempting to load its last save state and failing.

Can anyone confirm this?

...is it because you are trying to load 64k into 32k? mGB v1.1.0 is only 32k - maybe see if that works?

Thanks for pointing it out.

Have you tried using commas instead of ellipsis

I only have one and had to shell out 9 bucks for it. I might try ... though right now I got a copy of mGB to work (except for right after startup) ... and the cable seems to send everything just fine ... notes, pitch bends..

After a few more tries with different combinations DMG / ROM and a lot of flashing things around I managed to get a version of mGB on the Game Boy that looks weird until you press B once, at which point it returns to a functional state. I'm able to send MIDI data there right now.

Still... this looks like it's still not supposed to be that way. In Gambatte for example I don't have to press anything to get it to look right. I've not tested it everything works, but I can send on all 5 MIDI channels and the corresponding sound channels respond with the sounds I've set up

Tried a different link cable? Could be bad cable or interference issues

does the mgb even work? mine looks okay but seems not working on nanoloop 1.6.3

It gets even weirder... the ROM I flashed on B as shown in the photo above is behaving differently on 2 of my 3 DMGs without reflashing it in between. The screen you see above only happens on my green Play it Loud DMG. On the grey DMG and my black Play it Loud DMG it's looking differently (it's not cycling through the charset but is still not looking right).

When I flash the ROM on the two other DMGs it's even more broken, only displaying random horizontal lines or segments of lines ... I don't know what to think of it. I'm genuinely stumped.

They're all unmodded, the PIL Game Boys have DMG-CPU-08, the grey DMG has DMG-CPU-06, so it's also not a CPU issue. Batteries are all fresh.