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 Post subject: 2A03 Synth
PostPosted: Wed Jan 04, 2006 1:06 pm 
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Would it be possible to actually build a hardware synth around the 2A03 sound chip? I'm contemplating ideas for my senior project and since I'm trying to go for my EET degree, I'm just thinking up ideas here and there.


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PostPosted: Wed Jan 04, 2006 2:02 pm 
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midines

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 Post subject:
PostPosted: Wed Jan 04, 2006 2:13 pm 
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well, thats all said and good, but i dont want to blatently rip someone else's idea off.


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 Post subject:
PostPosted: Wed Jan 04, 2006 3:38 pm 
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The 2A03 is in essence a 6502 CPU with gamepad input, audio output, and two specialized DMA channels. It has 22 registers to manage those features.

Do you want to strip the 2A03 from the NES board, or do you want to leave it in place and make a synthesizer cartridge? Both are possible.

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 Post subject:
PostPosted: Wed Jan 04, 2006 10:33 pm 
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Using the NES would let others use your design easier, but I'd like to see (or do it myself eventually when I have time :P) one based around the cpu only (like the SID synths) so you could get a bit better quality from the signal.


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 Post subject:
PostPosted: Wed Jan 04, 2006 11:11 pm 
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gannon wrote:
Using the NES would let others use your design easier, but I'd like to see (or do it myself eventually when I have time :P) one based around the cpu only (like the SID synths) so you could get a bit better quality from the signal.


I did this awhile ago using a very simple CPLD and the NES CPU and some other thingies. It's called "HardNES" and pics of it can be found here:

http://tripoint.org/kevtris/Projects/hardnes/index.html

I was thinking some day it'd be nice to make another one with more sound chips and such, but it never happened. These days, I guess I could make it on an FPGA using that NES FPGA core I have designed.

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 Post subject:
PostPosted: Thu Jan 05, 2006 5:25 am 
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What about something more complex, such as x slave CPUs running some kind of interface code, controlled by a main CPU or micro, allowing for multi channel sound....?


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PostPosted: Thu Jan 05, 2006 12:07 pm 
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If you have several 2A03s running in polyphony, then you defeat the purpose of using a 2A03 for its distinctive sound, as they could all just be set to play samples out $4011. You might as well just use a wavetable chip loaded with the stereotypical 2A03 waveforms (12% pulse, 25% pulse, 50% pulse, 75% pulse, and 32-step triangle).

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 Post subject:
PostPosted: Fri Jan 06, 2006 5:22 am 
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But this is for his senior project - it would take some EE talent to arrange such a circuit, depending on the number of 2a03s used. No one says you have to use samples for everthing and not use the 2a03's distinctive sound...

I suppose you may as well toss your toaster out the window and use nintendulator for everything too.

Your post confused me: Am I missing something?


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 Post subject:
PostPosted: Wed Jan 11, 2006 9:35 pm 
tepples wrote:
The 2A03 is in essence a 6502 CPU with gamepad input, audio output, and two specialized DMA channels. It has 22 registers to manage those features.

Do you want to strip the 2A03 from the NES board, or do you want to leave it in place and make a synthesizer cartridge? Both are possible.


Well, personally, I'd like to strip the 2A03 from the NES board and use a keypad input to program in sounds. (is that even possible?)


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 Post subject:
PostPosted: Wed Jan 11, 2006 9:58 pm 
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sorry about that, i had forgot to log in.


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 Post subject:
PostPosted: Thu Jan 12, 2006 9:55 am 
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The 2A03 contains the NES CPU and APU. The only way you can write to the APU is through the CPU, so you'll need to provide some memory for the program and have that read some external source for data and write to the APU.


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 Post subject:
PostPosted: Thu Jan 12, 2006 12:57 pm 
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Ah, so it would end up something like Kevtris's HardNES. :? I seriously don't want to jack his idea. But it would be cool to make something like that for sure.


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 Post subject:
PostPosted: Thu Jan 12, 2006 1:39 pm 
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It would be pretty much like a NES, just without the PPU. :)


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 Post subject:
PostPosted: Thu Jan 12, 2006 2:05 pm 
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And you'll still need some sort of display for the instrument builder, so you might as well keep the PPU.

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