Search found 45 matches

by skrasms
Sun Sep 12, 2010 10:48 pm
Forum: NES Hardware and Flash Equipment
Topic: 2A03 Chip used as a synthesizer
Replies: 29
Views: 9157

http://www.robotshop.com/leaflabs-maple-32-bit-arduino-compatible-microcontroller.html this one specifically. The init code is still not letting me make noise. I really want to get the init code working, because without resetting by unplugging and plugging the whole thing back, I get erratic result...
by skrasms
Sun Sep 12, 2010 4:59 pm
Forum: NES Hardware and Flash Equipment
Topic: 2A03 Chip used as a synthesizer
Replies: 29
Views: 9157

jarek wrote: ...I'm upgrading my processor soon (getting a 72Mhz ARM beast =3 )...
Cortex M3?
by skrasms
Thu Sep 02, 2010 9:41 pm
Forum: NES Hardware and Flash Equipment
Topic: 2A03 Chip used as a synthesizer
Replies: 29
Views: 9157

Hey Jarek, what kind of equipment do you have available for debugging? Do you have a voltmeter or are you flying completely blind? The example set of instructions you posted are pretty complicated for an initial bring up test, despite looking simple. You're trying to get audio out when you don't kno...
by skrasms
Fri Aug 27, 2010 8:46 am
Forum: NES Hardware and Flash Equipment
Topic: Buying 2A03 chips by themselves
Replies: 7
Views: 4846

A couple years back I bought fifty or so from Mikesarcade to use in an eventual 2A03 synth. I'm not sure what the price hike is about. $25 is 500% of the old price. Recently I've seen either the G or H version for $0.75 from "black market" distributors like digchip, but all my correspondence with th...
by skrasms
Mon Jan 11, 2010 9:33 am
Forum: NES Music
Topic: Bit Depth and Sample Rate of NES Waveform and DPCM Chans?
Replies: 10
Views: 12796

Any signal from the NES, Game Boy, or similar designs based on a variable-rate sample-and-hold DAC can be represented as a sum of Heaviside steps . For example, a square wave consists of two steps per period, one positive and one negative. So one way to render the signal is to make a set of pre-fil...
by skrasms
Sun Jan 10, 2010 11:20 am
Forum: NES Music
Topic: Bit Depth and Sample Rate of NES Waveform and DPCM Chans?
Replies: 10
Views: 12796

Take the triangle wave, for example. It does not have a constant sample rate. It has a constant set of values that get read back at different sample rates to produce different pitches. It's more manageable than that -- the NES always generates audio at 1.8MHz. Each of the audio channels change (or ...
by skrasms
Sun Jan 10, 2010 1:50 am
Forum: NES Music
Topic: Bit Depth and Sample Rate of NES Waveform and DPCM Chans?
Replies: 10
Views: 12796

wow, i didn't even know most of that stuff. Different sample rates!! interesting. I should look into making a shift register for random values in hardware. Never heard of that one. Thanks for all of that information. What doc gave you all of that? (Brad Taylor's? I'd assume it's that one, cause it'...
by skrasms
Sat Jan 09, 2010 7:05 pm
Forum: NES Music
Topic: Bit Depth and Sample Rate of NES Waveform and DPCM Chans?
Replies: 10
Views: 12796

Given how you asked your question, it sounds like you're thinking in terms of PCM audio. It's a little bit different when talking about what the 2A03 does. Take the triangle wave, for example. It does not have a constant sample rate. It has a constant set of values that get read back at different sa...
by skrasms
Sun May 17, 2009 8:18 pm
Forum: NES Hardware and Flash Equipment
Topic: 2A03 in the Wild (Running It Standalone)
Replies: 9
Views: 3893

What is the LA that you are using? I've been looking for a cheap USB-based 8/16 channel LA for a while. I never seem to find one cheap enough to get it 'under the radar'. :roll: It's a Saleae Logic. It's pretty slow (~16MHz) and only eight channels, but it can record long spans of time. It has deco...
by skrasms
Sun May 17, 2009 1:21 pm
Forum: NES Hardware and Flash Equipment
Topic: 2A03 in the Wild (Running It Standalone)
Replies: 9
Views: 3893

I changed my system so that power switches on while RES is held low, and after a second I tie RES high. I don't get the counting pattern at all anymore. The chip now starts up like this: http://www.skrasoft.com/blog/blogfiles/2A03/startup5.png Here's a slightly closer view http://www.skrasoft.com/bl...
by skrasms
Sun May 17, 2009 9:56 am
Forum: NES Hardware and Flash Equipment
Topic: 2A03 in the Wild (Running It Standalone)
Replies: 9
Views: 3893

Also are you resetting the thing? You need to reset it. When and why does it need to be reset? When I first made a 2A03 synth before, I had to play around toggling VCC and RES to get it to actually work. I'd like to understand what is supposed to happen :) Right now I have the reset pin tied to VCC...
by skrasms
Sun May 17, 2009 9:49 am
Forum: NES Hardware and Flash Equipment
Topic: 2A03 in the Wild (Running It Standalone)
Replies: 9
Views: 3893

There are two different DMA paths in the NES: the $4014 blit-sprite-memory, which always starts reading from an address $xx00 and writes to $2004, and the DPCM which starts reading at $xyz0, x≥0xC, z={0,4,8,C} and goes for 16*w+1. Looking at the timing diagram, this looks like * read from 0, write ...
by skrasms
Sat May 16, 2009 5:09 pm
Forum: NES Hardware and Flash Equipment
Topic: 2A03 in the Wild (Running It Standalone)
Replies: 9
Views: 3893

2A03 in the Wild (Running It Standalone)

I've been doing experiments with a 2A03 by itself for a synthesizer, and I do not understand some of the results. This test was conducted to see what happens on startup, when the chip first gets power and a clock. The setup is very simple: D7-D0 are tied through 10k ohm resistors to ground. When the...
by skrasms
Tue Apr 07, 2009 7:23 pm
Forum: NES Hardware and Flash Equipment
Topic: NES Logic Levels
Replies: 27
Views: 10879

whoa! it works on Linux and OSX too, but only 8 inputs and 24MHz? Know a better one that might work on a machine I own (I use Linux and OSX so either one). It would be nice if I could do more like 24 inputs and capture writes to mapper registers for example. I do have a use for the Saleae at work j...
by skrasms
Sun Apr 05, 2009 10:37 pm
Forum: NES Hardware and Flash Equipment
Topic: NES Logic Levels
Replies: 27
Views: 10879

It's a Saleae Logic. It has terrible specs, but it looks really pretty and is great for simple data logging over long spans of time.