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Falonn

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Posts posted by Falonn

  1. Posted

    Back in 2014 (as a kind of capstone project during a year where I focused on self-learning electronics), I made a little DB9-to-USB adapter for Colecovision controllers.  The new idea was the inclusion of two ports so you could connect a Roller Controller.  There is a little switch to make it behave like a standard mouse so you can use it in emulators that have Roller Controller support... or just use it as a trackball in Windows or whatever because it's fun. :D

     

    The video mostly focuses on the electronics, but it does show the thing in action near the end:

     

     

    This was also before I knew anything about designing for 3D printing, so the case isn't great.  It mostly does the job, but that unintended sliding action is the part of the project that I'm still the least happy with.

     

    I didn't know about this community back then, so I never really shared it with anyone.  Now that I do know about this place, I finally get to share it six years later. :D

     

    All the files are on GitHub if anyone wants to try making one.  The PCB includes an ISP header, so it should be easy to program the microcontroller with one of those $7 USBasp thingies from Amazon.

    • Like 6

  2. Posted

    I don't have any advice, but I'd be interested to hear the answer, too.  The quadrature scheme used by each axis should prevent anything like static or noise from causing problems like that.  How strange.  That's amazing that it's so repeatable!  I've never seen this with my CV + Roller Controller + Slither combination.

     

    How much force is required on the ball to prevent the motion?  Is it only the slightest touch from a finger tip (like a touch-sensitive lamp)?  That would indicate some electrical fishiness.  Otherwise, if it takes more force, that would point to something mechanical.

     

    Do you have both controllers plugged into the Roller Controller's pass-through ports, or only one?

  4. Posted

    Nice work.  That output looks great.

     

    Can you confirm whether the audio still works on the machine?  I haven't been following the thread closely, but last I saw, the audio subsystem relied on a clock output from the '9918A that isn't there on the '9928A.

    • Thanks 1

  5. Posted

    For what it's worth, I saw this all through development, too.  The Framemeister is razor sharp with zero noise.  I always saw faint jailbars through the OSSC when against a black background.  But making the offset changes in step #10 of the install guide cleaned it up.  All that's left on the OSSC afterward is a very tiny bit of overshoot in rare cases.  (The Framemeister is also able to clean that up somehow, too, leaving emulator-like, essentially perfect output.)

    • Like 1

  6. Posted

    Interesting, the hand-drawn version mentions a TMS9318A for the VDP with a hastily corrected "9929A" written above it.  Maybe they were planning to use some future VDP product that never materialized?  And designing it for both styles of output explains why all the jumpers are there for choosing between composite and component'ish output.

     

    It also looks like the hand-drawn schematic must have been the source of the SGCCK vs. SGC CLK naming discrepancy on either side of W104.  The same names are used on the same pages in the same places as the other PDF.

  7. Posted

    10 hours ago, Ikrananka said:

    The attached may help - it's specifically for the 4A and includes the schematics.

    That's the same link I included 25 posts ago, back on page 3! :lol:

     

    Though, like ChildOfCv noticed, be careful scrolling through it too fast: it contains two sets of schematics, one for the 99/4A and another for the 99/4QI... whatever that is.

     

    11 hours ago, ApolloBoy said:

    After this I might be interested in pairing the TMS-RGB with an internal RGB to component converter...

    Yeah, like Ikrananka was saying, this would be a roundabout, inefficient path.  The output signal is almost natively component.  So you'd be going component'ish --> RGB --> component, where at least that first step (through the LMH1251) sucks up a lot of power.  A component-only board would only require half the parts, half the power, potentially half the PCB size (or possibly double the component size to make it easier to solder by hand?), and less than half the cost because it wouldn't need the expensive LMH1251 anymore.

     

    I'm not sure how useful a component version would be to the wider community, seeing as most new TVs are dropping component inputs completely.  But, after that laundry list of benefits above and knowing that it's just TMS-RGB with a few things removed, I'm interested now just out of completeness.

  10. Posted

    6 minutes ago, ChildOfCv said:

    Where do you see the CPUCLK going, other than to video pin 2?

    There are two pin 38's coming out of the chip.  On the left side, pin 38 goes to the SGCCK signal (through grounded shield W104).  On page 23, there is an "SGC CLK" at the far right that also passes through a grounded shield named W104, so I'm guessing they just changed signal names (accidentally?) between pages.  (All of these 1980's TI datasheet are riddled with errors, so it wouldn't surprise me.)  From there it appears to go to the audio chip and (through another jumper) to some "GROM" stuff.

  11. Posted

    No, not at all. :D

     

    I was able to find a 99/4A schematic though (on page 20 of this PDF) and it looks promising that you might not have to modify the board beyond adding/removing a couple jumpers.  It looks like it might have been designed flexibly to accept either VDP.  The J201 header is even labeled with B-Y and R-Y.  The main trouble I see is that the CPUCLK output line (which isn't a clock at all on the 9928A) appears to actually be used somewhere else on the board for something.

     

    It might be worth trying to find an account from someone that has already done the 9918-->9928 conversion (with instructions for changing the jumpers) before trying to RGB mod it.

  12. Posted

    15 hours ago, aleomark said:

    tms-rgb web shows:

    ”This small adapter board can unlock the potential of many 8-bit systems from the 1980's including the Colecovision, MSX, SG-1000...”

    I tried my best to find a list of systems that use the 9928A, but there is a lot of unreliable/conflicting information out there!  I've already had to amend that list once.  Does this mean I got the SG-1000 wrong, too, and that it should be removed from the list?

     

    7 hours ago, ApolloBoy said:

    You can if you swap the TMS9918 with a TMS9928 and add a crystal oscillator circuit...

    For composite (or RF) out, you'd need an extra one, but just for the VDP's general operation, I think the datasheet shows that they both use the same 10.738635 MHz clock.  The only differences I see between the two are on three pins:

     

    pin 35: EXTVDP on the 9918A / B-Y on the 9928A.

    pin 36: composite video output COMVID on the 9918A / Y on the 9928A.

    pin 38: the "typically not used" CPUCLK on the 9918A / R-Y on the 9928A.

     

    It would be easy to just leave those three 9928A pins disconnected from the rest of the original circuit board by leaving them bent up or by cutting a trace on the board or something like that, except there is one key requirement laid out in the datasheet: they require a small "load circuit".

     

    For pin 36, this should already be present, because it's required for both chips:

     

    1865579076_9918Aloadcircuit.thumb.png.e72d3a6940266f28a6eeb7ceb424ee5c.png

     

    For pin 35 and 38... who knows what circuitry is already there.  But there needs to be a resistor to ground on each:

     

    1122297018_9928Aloadcircuit.png.71f36cc42052d12f1c08f8c6569303d8.png

     

    If there is much else going to/from those pins, I'd worry that whatever the TI-99 board has in place for EXTVDP and CPUCLK, it might be causing the trouble you're seeing on your TV screen there.

  15. Posted

    For what it's worth, I don't ever expect to sell any myself.  The list to keep an eye on is the "People offering pre-assembled TMS-RGB kits" on this page.  (And for anyone interested in making/selling them, just let me know and I'm happy to add you to that list.) :D

     

    ... or just send your system to Ruggers Customs and he'll install one for you.  (There's a list for that too, but he's the only one on it.)

  16. Posted

    As a footnote: I went back and annotated the "TMS9928/29 and TMS9128/29 Interface to Color Monitors" document, otherwise known as the "TMS Doc" earlier in this thread.

     

    This version highlights all (9!) known mistakes, including a new pair I only just discovered in the description of the blue channel conversion.  If we discover more, I'll keep it updated in the same place.

    • Like 1

  18. Posted

    45 minutes ago, Ruggers Customs said:

    A write up on Retro RGBs website can be found here.

    https://www.retrorgb.com/new-colecovision-rgb-mod-available-tms-rgb.html

    It would be cool to see RetroRGB's own Colecovision page updated, too.  They still recommend ColecoRGB there.  I'm still new in the community and don't really know how to reach Bob directly.

     

    It wouldn't hurt to show samson7point1 your photos from the HDRetrovision cable to dispel his questions, Jimmy.  (Search "This doesn't really make sense" on that page). ;)  If there isn't digital quantization going on inside that thing, I'll eat my hat... or whichever colloquialism you prefer. :P

    • Like 1

  20. Posted

    4 minutes ago, doubledown said:

    There should be plenty available on ebay, it was an off the shelf part.

    At one point during my TMS-RGB testing, I was sure I had fried my Colecovision's VDP after I accidentally bridged some live pins.  I was also able to readily find domestic, used replacements on eBay for $10.  (Of course, while the replacement was still in the mail I discovered that my VDP was somehow just fine.) 😅

  23. Posted

    Thanks for the clarifications, everyone.  I think it'll be better if I remove it from the list.  I'd rather have the PAL version be covered by the "and more" at the end of the list than have some unsuspecting NTSC TI-99/4A user go to the trouble of building or buying one of these things just to find out it won't work for them.

     

    Eventually as more of these RGB boards make their way out into the wild, the right answer will be to add an "actually tested on" compatibility list as those reports come in.  In the meantime, it's better to be safe than to inadvertently make someone else sorry.

     

    Thanks again!

    • Like 2

  25. Posted

    7 hours ago, Omega-TI said:

    Was this thing developed because the other product was no longer available?

    Do you mean the ColecoRGB?  There is a more complete version here, but the shorter story is that all three or four of the widely-known circuits had at least one problem.  Almost all of them suffered from the "too much blue" problem (due to an interesting choice on TI's part when designing the VDP) and pixels that are too narrow when coming from black (making text very hard to read) was a problem unique to ColecoRGB (among others).

     

    TMS-RGB combines the strengths of each while working around the weaknesses of each.  You don't need an oscilloscope during install anymore to tune the colors, etc.

    • Thanks 1
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