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rbairos

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Everything posted by rbairos

  1. (Short answer for anyone interested: Most likely pixel clock and cycle are always aligned for the 2600, but 6502 emulator was left more general for historical reasons.)
  2. I think that should read: At the start of each line, does pixel 0 always coincide with the start of a cpu cycle? (though it could be the start of cycle 2 or cycle 3 etc)
  3. Thanks, that what I assume as well. I'll drop a note with the Stella people for clarification. Cheers, Rob.
  4. Hello, I know the TIA runs three steps for every one cycle of the 6507, but my question is: At the start of each line, does pixel 0 always coincide with the first cycle of an instruction? Trying to force a counter example, but having difficulties. Specifically looking at the stella code: void TIA::onHalt() { mySubClock += (TIAConstants::H_CLOCKS - myHctr) % TIAConstants::H_CLOCKS; mySystem->incrementCycles(mySubClock / TIAConstants::CYCLE_CLOCKS); mySubClock %= TIAConstants::CYCLE_CLOCKS; } I can never get mySubClock to exit that function with a non-zero value. That is, myHctr is always an example multiple of 3? Thanks, Ro.
  5. So I got a kernel working with this method. Works on stella emulator, light sixer, even the Flashback 2. I should be able to try out Colecovision adapter soonish.
  6. Alright, ended up using a length of spare svideo cable (had 4 conductors), and a DB9 connector (with internal terminal strip). Not factory identical, but tidy enough and works and saved the 40 year old bases from landfill.
  7. Just a followup. I received the 9 pin cable over a year ago and finally decided to splice it in tonight. Was going well, until another break in the original atari cable. Then another. It was looking pretty monstrous so going to rethink this cable replacement fix.
  8. Alright here's the update: Spoiler: it works again. What we did: 1. First we cleaned all the cartridge edges, and the connector. We used white erases, deoxit and isopropyl alcohol. Unfortunately same problems remained. 2. We then were able to take the case apart (just 8 screws on the bottom, without disturbing the metal front plate), though this took some careful fiddling. We were also able to remove the shielding which luckily was just soldered on one spot, removing some easily accessible screws. This gave access to the switch, which we just sprayed with deoxit without removing its case. We also inspected for bad solder joints, and gave the board a gentle cleaning with a toothbrush and isopropyl alcohol. Unfortunately same problems still remained. 3. Finally we desoldered the power switch main upper casing from the board. (Two large solder points) This revealed six contact points, 2 of which were black, the rest yellow. This cleaned up easily to a shiny silver color. The problem still remained, but after a couple of switch cycles, all was finally good consistently. So our success rate went from about 10% to 100%. Thanks for all the tips! Rob.
  9. Thanks. So a pull down resistor on each, and possibly low pass filtering?
  10. Hello. Looking through the atari NTSC schematics on this site, I notice, Pin 8 of ic 6532 has a tie to ground through a cap. This corresponds to pin 1 of right joystick. Why only that pin and not the others? Thanks, Rob.
  11. Sorry, busy time of year, but I hope to apply these techniques very soon. Will definitely report back.
  12. Thanks that makes a lot of sense. Luckily I already have deoxit and isopropyl alcohol and white erasers at hand. -Rob
  13. Hello a friend just acquired a colecovision and 2 carts (Smurf and Cabbage Patch Kids). Cabbage patch rarely starts up, and Smurf starts up with several artefacts half the time. Any advice how to start diagnosing? From the little I know, it may be a DRAM issue? In which case, I should look for dry solder joints and/or consider a DRAM update kit which foregoes the multiple voltages? Thanks for any info, Rob.
  14. Thats what I meant. Having the samples fetched at regular intervals is easier to accommodate over having varying kernel routines reserve same cycle positions for it. Good point about 300kHz sampling. Though I think in this case, real hardware could produce > 15.75khz content for example, were it immediate AUDV0 updates. Luckily in my project, I think I can accommodate hitting AUDV0 once, at the same cycle each scanline, after much more fiddling. -Rob
  15. It would simplify things greatly to not have to obsess when during a scanline audio is updated (though that's kinda the fun). Assuming this may be different for different atari versions as well. Cheers.
  16. Hello. Is the output volume updated exactly when AUDV0 is changed, or it latched only at a specific clock cycles? (What about AUDV1 while on the topic?). Thanks very much, Rob.
  17. I'll have to verify, but was using stella to note the cycle clock. But in the case where it does work (72, or 71 base 0), should I expect it to work on most systems then? Aiming for heavy-sixer, and FB2 mod. Thanks, Rob.
  18. So cycle 71 (HMPx == 0) does the trick to shift back 8 pixels. Funnily enough, if its at 72, the counter does tick left 8 pixels, but then shifts back to original position.
  19. Yah, I was aware the metal would change the adjustment while inserted, but I read some strongly worded old posts here that any metal edge could introduce cracks into the brittle core. I did all my measurements several times with the tool removed to make sure it was where I needed it. One thing to note, I did this on an analog TV with its own manual fine tuning, so Im not 100% sure I adjusted this optimally for actual channel 2/3 frequency. Cheers, Rob.
  20. Okay amazing tip. I need to review my kernel to see if I can fit this in.
  21. Hello, doing some work shifting sprite back and forth each line, but am I correct in thinking the maximum back-n-forth shift is 7 pixels? That is, I do quite a bit of rendering throughout the line, and near the end I need to shift things forward or backward 8 pixels for the next line. I realize HMP0,1 only allow +8 through -7, so am I out of luck? Thanks, Rob.
  22. For anyone interested, I ended up buying a set of nylon anti-static adjustment tools from amazon for about $15. Unfortunately, none fit properly. So I **carefully** inserted a 3/32 hex allen key through the audio coil, so that it traveled all the way through, making contact with the bottom of the unit, I then was able to turn carefully to adjust the audio level. I think I got it better, but unfortunately never quite got rid of the buzz entirely. Channel 2 however (instead of channel 3) has no static or buzz on the audio at all it seems. Maybe that's a different issue, but I may just go with channel 2 for a while. Cheers, Rob.
  23. Hi Everyone. I have a light sixer, that the image is okay, but the sound has some static. When I switch from channel 3 to 2, the image goes staticky, but the sound is very clear. Am I right in concluding I need to adjust the vertical red/pink choke piece to adjust the audio carrier ? If so, it just requires a *plastic* screwdriver to carefully adjust? Any online recommendations for one? Thanks, Rob.
  24. Thanks for the update. Yah, I would suggest a jumper, physical switch etc for hard selecting between 2600 mode and enhanced mode. I have to assume there's way to much legacy code that relies on those upper address lines being ignored, in their execution.
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