Subject: Re: [stella] Fpga2600 Status Update From: "Kroko" <Nil.Krokodil@xxxxxxx> Date: Sun, 20 Mar 2005 09:32:34 -0500 |
Hi Adam ! What a nice piece of VHDL code ! I will better not ask how may hours you already spent on this :-) >(This is where you can make me feel good by cheering me on, if nothing >else) *CHEER* Are you planning to release a cleaned version of the TIA schematics with modern, readable symbols where all the questions are answered that you had to find out in the last few month ? Armin ----- Original Message ----- From: <adam@xxxxxxxxxxxxxxxx> To: <stella@xxxxxxxxxxxxxxxxxx> Sent: Sunday, March 20, 2005 4:26 AM Subject: [stella] Fpga2600 Status Update > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > [regarding http://sourceforge.net/projects/fpga2600/ ] > > It's been a while, so I thought I'd update. > > As you know, the RIOT code is complete and tested. > > I've been pounding away at the TIA code recently, mostly spurred on by > releases of various commercial projects and another similar open source > effort. (The author of that other effort hasn't released any code yet, > but promises he'll make it open source when he's done). At this point > I don't care so much about finishing first as I do about finishing; > I picked this project up to learn something new, and I'd like to see > it through. (This is where you can make me feel good by cheering me on, > if nothing else). > > Regarding the most recent tia.vhd checked into CVS on sourceforge... > (that's http://sourceforge.net/projects/fpga2600/ for those of you > playing along at home). > > Analog output on the audio pins is a bit problematic for an FPGA. > I've replaced the analog AUDIO0 and AUDIO1 pins with 4 bits each. > I'll feed these into a cheap resistor ladder DAC and then into my 2600, > as well as a pair of RCA jacks. > > Similarly, I've decided NTSC video is a bit of a pain; the current > code outputs 4 bits of color, instead of the single phase shifted > colorburst signal. I plan to feed these plus the three luminance bits > into a lookup table (basically a ROM) to get 4 bits each red, green, > and blue, then use these to drive another set of cheap resistor ladder > DACs which will drive the component colors on a VGA monitor. I expect > the picture to be sharp. :) > > As you'd probably guess, this means the DELAY pin is completely ignored. > I'll leave true NTSC up to someone who's up enough on their analog to > produce the correct phase shifted colorburst signal from those 4 bits > of color. I suspect, however, given the current target audience and > expected usage of this code, that it will never actually happen, which > is fine with me. Now that we live in the 21st century, I think it's ok > for the relic of NTSC to die. This project is all about preserving the > look and feel of the old games using new technology anyway. > > Simulations of the code look good, and I've ordered parts to interface > my developer board to my 2600, and to a VGA monitor. I'm hoping that it > will go as smoothly as my RIOT testing went. If it does, then I should > have some good screenshots to share. > > Once that's done, the next step will be to evaluate the 6502 core I dug > up way back when... > > - -- > adam@xxxxxxxxxxxxxxxx http://cuddlepuddle.org/~adam > KG6GZR http://cuddlepuddle.org/~adam/resume.html > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.2.1 (GNU/Linux) > > iD8DBQFCPNukyvXf5Z0z5zERAlyLAKC1TA2aJnGzHUKNYW9mzrFY4WJ4WACdGNdL > o+xYR8w2NXdMyLRQbXtDX2Y= > =dLrs > -----END PGP SIGNATURE----- > > > Archives (includes files) at http://www.biglist.com/lists/stella/archives/ > Unsub & more at http://stella.biglist.com > Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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