Search found 65 matches

by themrcul
Wed Oct 10, 2018 5:39 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

You guys are amazing, thanks. How do you know all these things!? Anyway, so if my interface between the MD and the ARM chip is 8bit, I can just hook up the lower 8 data lines, and hook the write high/write low to an AND gate, so that 0V = WRITE, 5V = READ. The ARM chip I am looking at now is the ATS...
by themrcul
Wed Oct 10, 2018 12:39 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Awesome, thanks heaps Mask.
Just to confirm, for 8bit writes, only the first 8 data lines are used, is that correct? Do the upper 8 data lines (D8-D15) go to 0V? Or is their state indeterminate?
by themrcul
Tue Oct 09, 2018 9:25 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Hi everyone, 8 weeks ago my wife and I had our first baby so things have been very busy but I have been planning and thinking about this project lots regardless! I now have a question about the pins on the cart and how write low/high works. It's difficult for me to explain so I'll try to use example...
by themrcul
Fri Aug 24, 2018 4:00 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Awesome, thanks Tiido. I think I'll purchase both and experiment when building the op-amp circuit. Can't wait to get started. Need to design the first PCB that holds most of the components together first though!
by themrcul
Thu Aug 23, 2018 10:44 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Hmmm. It's a shame the NJM2073 looks to be low sound quality.. I have found plenty of linear power regulators which take in up to 6V and spit out both 3.3V and 2.5V - so the mid-point voltage is easily solvable if necessary. In that case, which op-amp would you choose Tiido if you were me? Do you kn...
by themrcul
Tue Aug 21, 2018 11:13 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Thanks Tiido. I have done lots of learning since your last post. I know now that the LM358 for example will only output a puny amount of current, and not enough to surmount 75ohms on a model 1 MD, that is why the output goes through a power buffer circuit that you have designed there. In that case, ...
by themrcul
Sat Aug 18, 2018 2:56 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Thanks so much for that detailed reply Tiido. So, there isn't a problem with sending a 0-5v signal through to cart B1/B3? Isn't the Mega Drive expecting a -1v to +1v signal on those lines? If that's not a problem, that's good news. With the diagrams you kindly posted, how should I go about working o...
by themrcul
Sat Aug 18, 2018 12:35 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Ok, so I just learned that the LM358 op-amp can't create negative voltages from nowhere, so the signal will simply clip when attempting to drive it lower than 0V. Back to the drawing board on that plan at least! The best I can come up with now is some sort of linear regulator to get +1V from the +5V...
by themrcul
Sat Aug 18, 2018 9:42 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Hey fellas, I am gearing up to purchase a few discovery boards for an ARM to test some code with, and hopefully get it playing sound as a first step. What I am wondering is how best to hook the DAC outputs from the ARM chip up to the MD cart side on B1 and B3. From what I have read is the MD expects...
by themrcul
Wed Aug 01, 2018 12:14 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Thanks guys, your help is invaluable. Great news on the Z80 also pulling /TIME low when accessing the /TIME data range. That means that the Z80 can send "play sound" and "play instrument" commands to the ARM chip! I have looked now at using 3.3V flash on the cart pcb extensively. It seems that if th...
by themrcul
Sun Jul 29, 2018 9:30 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Thanks again Tiido for your advice. IT appears this setup is no-where near as simple as I was hoping it could be! But I thank you for taking the time to advise me, I really appreciate it. You are correct about the sellers on AliExpress - it turns out they are not new parts, but pulls. However there ...
by themrcul
Tue Jul 24, 2018 11:39 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Thanks guys, Re: Chilly Willy, I did read the datasheet, but didn't understand that would happen. I scoured the doc for mentions of what voltage it would output at but didn't realise it would output at generally what is input. Fantastic! With 512KB of flash I hope that will be enough to hold all the...
by themrcul
Tue Jul 24, 2018 2:40 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Hi Tiido (and others!), I have done lots of research about possible cart design options, but I have a few more questions that could help me immensely! I think I have found the memory chip for code, graphics and music assets: the M27C322. Available for ~$1 on aliexpress, 32megabit, parallel, 5v, < 10...
by themrcul
Thu Jul 19, 2018 1:21 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Re: Cart Design Questions

Thanks very much for taking the time to help TmEE. I have done hours of learning since, and hope to post what I've learned plus a question or two later on, but it's not ready yet. But I have found 5V 32MBit Flash/Eeproms available, and a suitable DSP for augmenting the sound system of the MD. Just n...
by themrcul
Tue Jul 17, 2018 2:45 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 26
Views: 2231

Cart Design Questions

Hi all, I am hoping to get some feedback on the design of card needed for a commercial game. I am not ready to produce something, but I am the kind of person who likes to have most questions answered before starting something! I have more than a decade of programming experience, in pure C (Wii/PS2/P...