DMG Motherboard Development (Page 2 of 6)

I'll most likely end up making the files public. I need to read through the different licenses I could use though. Ideally I'd like it to be open but non-commercial unless I know about/approve it. I hope I don't sound too selfish or whatever by saying that. I'd love for this to help get more development going in the community.

Well the main reason for that is my complete lack of any formal training with electronics. I'm no engineer, to say the least. However, I think that part works well enough to leave it alone for the time being. Besides, those pads were just thrown in after everything else as a "why the hell not?".

It works well enough as it is, at least when driving a high impedance, like a mixer/soundcard input/an amp. Don't fix it if aint broke.

Well... I used to believe that, until I heard the difference myself. It's true that DMG doesn't sound as horrible as GBC when unmodded, and that the modification doesn't (and doesn't really need to) improve frequency response. But what it does do is improve the signal:noise ratio, by both bypassing the amplifier, which adds noise, and providing a higher nominal voltage. This comes at the cost of higher impedance though, which does make the output unsuitable for headphones, but, again, works just fine for high-impedance inputs. If you're actually serious and want a clean recording, or less background noise when performing on a big PA, the mod is the way to go. If you're just starting out and hardly know how to use LSDj, it can wait.

if you need any assistance with PCB design, let me know.

since you are in EAGLE, i'm pretty proficient...  learning altium designer made eagle cad a cinch...  well, apples and orange, but altium can be like pulling teeth compared

but, yeah, if you need any advice/assistance, please let me know.  i'm happy to help how i can.  including the grounding plane issue.  which, tbh, is going to be an issue the way eagle handles this and the board is laid out. 

this goes to Rolf and Nex in particular, but to anyone else really.  i don't mind helping out with eagle.  its pretty fun honestly. 

also, be careful in eagle because the free version's license has some caveats concerning the making of things to sell.  the free version is meant for hobbyists really, not for commercial application.  last time i checked, they offered a single license thing to get past this...  but i don't know the cost.  altium ended up being substantially cheaper and more powerful for me personally...

i'd try to talk you out of eagle, but its too late

edit -- also, many of the eagle libraries are licensed as well, including the sparkfun one the last i checked (try the adafruit one instead).  meaning, you shouldn't use their footprint/silkscreen/etc...  i always make my own footprints in eagle though, except for caps and resistors really, and can help with this also.  or, can walk you through the basic process of doing this.  its pretty horrible the first couple times, but becomes very easy after you figure out what it is you are doing...

No, the modification I'm suggesting is for the internal work RAM. Has nothing to do with the external save RAM, that lives on the cartridge. However, my LittleFM LSDj file manager, that I like to namedrop, but actually can't seem to finish, does what you want by allowing the cartridge flash to be used as a save memory.

Actually, it's using external RAM chips.

Actually 1: People have already done that and made a FPGA implementation of the CPU. See: http://www.fpgb.org/
Actually 2: That should be possible to do in software with the current CPU and CPU speed, just that LSDj doesn't do it. (Although the HF vibrato is tasty!)

I agree with this, and also I would say that the only reason I can think of that Prosound actually does anything is because it bypasses some really crappy audio hardware. Unfortunately, most prosounds I have seen would also not have any shielding or filtering at all, so you'd still pick up noise from the surrounding address lines. Also, with the audio output basically connected directly to the CPU as many prosounds do, you're greatly increasing the risk of ESD damage to the CPU.

I would say the best sound quality on any gameboy, not just the DMG, would come from a combination of replacing the DC:DC converter with a better one, as well as bypassing the cruddy internal filter and amp circuit and instead running through a properly designed filter and op-amp.

low-gain: If you want to eliminate the need for an extra jack, the idea of using a new amplifier does make sense. But the current "Prosound" modification is easy to do, especially on stock consoles, and works well enough.

As long as you use the modification for high impedance inputs only (mixers/soundcards etc) there is absolutely no problem. In fact, it's not much different from the high impedance input of the DMG's own amplifier.

The DC/DC converter then... It does produce some ripple, but I don't think it's the main source of noise, at least not when bypassing the DMG's own amplifier. Where this is really a problem, it can probably be solved more easily with more filtering. The main problem with replacing it, though, is that provides -18V for the LCD in a small form factor, which you'd have to make up for.

This is just a scare tactic without much basis in reality. How about a real argument? Unless you're looking to eliminate the need for a dual output, or you're very keen on getting noise-free headphone sound, I don't see the need for a new amplifier.

Arfink: Picking up noise from address lines: Marginal problem. Insofar that this is a problem, it can be improved by tapping ground off of a location near where you tap the signals.

The ESD argument... No, just no. If you want me to elaborate on why this isn't a problem, I could.

Last edited by nitro2k01 (Sep 6, 2010 9:07 pm)