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TI99/4A Motherboard Replacement (In Progress)

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4 hours ago, rkrenicki said:

...the minimum quantity of 5 ended up around $18 per board after shipping.  

That's not as bad as I though, actually.  Interesting.

 

4 hours ago, rkrenicki said:

...so they are flood fills with thermal reliefs.  One giant 360x140mm(ish) copper pour.  This would help with EMI as well,...

Oh yeah, power and ground planes are really nice to have for sure.  It will probably never be tested like this, but I would be curious to know how the original board with the metal shield compares to your board with the power and ground planes.

 

4 hours ago, rkrenicki said:

... Ideally, I would like to find a way to change the internal GROMs out with an (E)EPROM too. ...

GROM / GRAM are not that tricky, but it does require some external circuitry to replicate the internal address counter.  The HDL for a GROM is not that hard, but that suggests some sort of programmable logic, and I don't know if you have posted your philosophy on the project goals and what you are willing / not willing to do.  Worst case, just put the GROM footprints at the same spacing and orientation as the originals, and let someone make an external plug-in replacement.  Best case, include a modern CPLD or small FPGA to replace the GROMs; but then you have the trouble of figuring out how to program them in-circuit, since one of the main benefits to having a replacement would be to be able to change the GROM code.

 

4 hours ago, rkrenicki said:

This one would be great.  4116s sure are a pain to find.  I have not seen this mod yet, but I will look around further.

I'm pretty sure I have seen circuits.  Check in the ColecoVision and MSX communities, I think that's where I saw such a mod.  It should not be terribly complicated.

 

4 hours ago, rkrenicki said:

I am very interested in this one as well.  Although it would be challenging to test since I have been on the F18A waitlist for years

:(  Yeah, I really am trying to get it done.  I'm pretty unhappy about the whole situation really.  We can probably get something worked out if you get to the point of needing to test, and the MK2 is not ready (which I hope it would be).

 

Alternatively you could replace the 9918A board area with the F18A design (FPGA, a few voltage regs, etc.) and not have to worry about the MK2. ;)  Also, with the FPGA you would not need to have the DRAM or any SRAM replacement for the 16K, so lots of board space recovered as well as less power.

 

However, again, I'm not sure how true to the 99/4A motherboard you are trying to stick to.  Eventually chips like the 9918A and 9900 will become hard or impossible to get, at which point, if we are still alive (or anyone cares about running real hardware), we will have to find or turn to programmable-logic solutions.  Although, there are also fabs these days that will reproduce chips on-demand, so maybe a custom run of the 9900 will be a thing.

 

4 hours ago, rkrenicki said:

... I am also not super married to the existing "offset" footprint of the DE9 connectors.. I may change them out with a more modern low-profile footprint.

This is a PITA rabbit-hole too.  I have spent quite a few hours looking at similar options for the VGA HD15 connector.  There are thin versions from a few vendors, but none of them have compatible footprints.  Then there is an in-between size footprint that seems to have a standard footprint.  And finally there are those really deep full-size versions.  I think the size is to also give mounting support, since those connectors don't always (rarely in retro home computers) have back-panel support and all the insertion force goes directly to the PCB.

 

 

Oh, another option might be to put an FTDI USB-to-serial IC on the board and wire it up to where a serial port would go in the memory map.  Make it a new serial device that is out of the way of the original serial ports.  This helps give options for in-system updates, if that becomes a thing, and if not, it is a nice serial port to connect to a modern PC.

 

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Posted (edited)

So, I have big dreams here.. and this is simply the first step.  This is what I foresee:

1) Stock Replacement Board - Full drop-in replacement with minor improvements.   <-- This is where I am today.

2) Stock++ Upgrade Board - Drop-in replacement with mods (SRAM Video RAM, ROM in (E)EPROM, Inbuilt Speech, GROM in (E)EPROM, etc)
3) My Dream TI99/4A Board - Full out upgrade board with many/all of the bells and whistles I want.   This will probably NOT fit within the stock case..  Could be a small stack of boards, cards on a backplane (similar to a Geneve in a PEB), or possibly a mATX board.   It would be similar in concept to Fabrice's TIny99, but with probably different mods and open source.

Each step would be a fork from the prior step.

Edited by rkrenicki
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1 hour ago, rkrenicki said:

So, I have big dreams here.. and this is simply the first step.  This is what I foresee:

1) Stock Replacement Board - Full drop-in replacement with minor improvements.   <-- This is where I am today.

2) Stock++ Upgrade Board - Drop-in replacement with mods (SRAM Video RAM, ROM in (E)EPROM, Inbuilt Speech, GROM in (E)EPROM, etc)
3) My Dream TI99/4A Board - Full out upgrade board with many/all of the bells and whistles I want.   This will probably NOT fit within the stock case..  Could be a small stack of boards, cards on a backplane (similar to a Geneve in a PEB), or possibly a mATX board.   It would be similar in concept to Fabrice's TIny99, but with probably different mods and open source.

Each step would be a fork from the prior step.

I wish you a lot of fun and all the best for your project and all of the others to come next 🙂

 

I know this feeling. These kind of projects have no end, we always want to add more and more features, like an infinite game. My TIny-99/4A v3 development came to the end. Now, it's time to release it and I already have new dreams, new ideas for futures projects: Two will be jointly put into execution: An Apple IIe upgrade (too many times postponed, time came to start it)  and the laptop version of the Tiny-99/4Av3 (some months ago, I worked on its features and feasibility and that's OK). Sure, all of them will be funny to create.

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10 hours ago, matthew180 said:

:(  Yeah, I really am trying to get it done.  I'm pretty unhappy about the whole situation really.  We can probably get something worked out if you get to the point of needing to test, and the MK2 is not ready (which I hope it would be).

I re-read what I had posted and I didn't want you to misunderstand me: I was not trying to take a dig at you,  I meant it in a joking way.

 

10 hours ago, matthew180 said:

Alternatively you could replace the 9918A board area with the F18A design (FPGA, a few voltage regs, etc.) and not have to worry about the MK2. ;)  Also, with the FPGA you would not need to have the DRAM or any SRAM replacement for the 16K, so lots of board space recovered as well as less power.

 

However, again, I'm not sure how true to the 99/4A motherboard you are trying to stick to. 

I am very open to this on the second or perhaps third iteration.  However, I do not know you feel about my desire to keep this open source if the Mark 1 version were to be included.  I also do not know where the particular Xilinx Spartan used is in its lifecycle.  (that sentence looks odd.. but sounds right when I say it out loud..)

 

10 hours ago, matthew180 said:

This is a PITA rabbit-hole too.  I have spent quite a few hours looking at similar options for the VGA HD15 connector.  There are thin versions from a few vendors, but none of them have compatible footprints.  Then there is an in-between size footprint that seems to have a standard footprint.  And finally there are those really deep full-size versions.  I think the size is to also give mounting support, since those connectors don't always (rarely in retro home computers) have back-panel support and all the insertion force goes directly to the PCB.

I was thinking something more along the lines of a "standard" DE9 connector.  Such as a TE 2301843-1 or Kycon K22X-E9P-N.   Something with some structure behind it, but would be quite a bit shorter than the ones that TI used.  I do not think that those super slim connectors would be appropriate without some sort of external bracket.

 

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20 hours ago, rkrenicki said:

I re-read what I had posted and I didn't want you to misunderstand me: I was not trying to take a dig at you,  I meant it in a joking way.

Yup, I understood, I was not taking offense; I'm just really frustrated with the pace of the MK2.

 

20 hours ago, rkrenicki said:

However, I do not know you feel about my desire to keep this open source if the Mark 1 version were to be included.

I fully intend to release the "MK1" (it was never called that, but it has become a backward-designation) when I get time to think about it, so this is not an issue.  Also, a version for the PCB is out in the wild when I uploaded it to CircuitMaker, and, as mentioned in other threads, the HDL was included with the Phoenix since I agreed to let that project use the F18A core (and I ended up getting pretty involved).

 

20 hours ago, rkrenicki said:

I also do not know where the particular Xilinx Spartan used is in its lifecycle.

I got a chuckle from that, due to the irony that you are making a circuit board where most of the main parts have been discontinued for over 30 years. ;)

 

So, I thought the Spartan-3 series had been discontinued as well, probably due to believing everything I read on forums.  However, I just spent an hour or so looking into it and found nothing from Xilinx that the Spartan-3 series is discontinued or EOL.  I found a forum response that gave this information:

 

https://forums.xilinx.com/t5/General-Technical-Discussion/Spartan-3-Product-Life-with-Spartan-6/td-p/675918

 

"There are no planned obsolescences.  Devices are discontinued when the volume gets too low or the fab no longer offers the process.
Xilinx gives one year notice of discontinuance for last time buys and another year to complete the last time buys."

 

On the Spartan-3E product documentation page, there are no notices of discontinuation other than for the Spartan-3A (not 3E) 208-pin QFP package.  There was a notice for specific "dies", but since we are not fabbing chips with Xilinx dies in them, I don't think that is a concern.

 

The Spartan-3 series is actually very popular and has components that are Automotive rated, as well as packages that are not offered in their other FPGA lines, like the 100-pin QFP that the MK1 uses.  It should also be noted that right now, at the time of writing, the Spartan-3E has great stock at Mouser and DigiKey, but the newer Spartan-6 that the MK2 uses is out of stock everywhere...  Not sure what that is all about, but it was very surprising to me.

 

The requirements of the MK1 are not too high and could be satisfied with a lot of FPGAs, so I would not really let that be a concern in your decision to take that path or not.  Also, with the amount of room you would have on the board, you could easily use a part with a 1.0mm pitch BGA, which are infinitely easier to route than the chip-scale and wafer-scale BGA parts (and BGA is the package of choice for FPGA manufacturers there days).

 

20 hours ago, rkrenicki said:

I was thinking something more along the lines of a "standard" DE9 connector.  Such as a TE 2301843-1 or Kycon K22X-E9P-N. 

Yeah, that looks like the "middle size" I was looking at for the HD15 connectors too.  However, I think the larger ones are the "standard" package, and anything smaller in a consistent footprint is pure luck that the manufacturers are getting along.  Kind of like hotdog vs bun packaging. ;)

 

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On 3/12/2021 at 8:52 PM, matthew180 said:

I got a chuckle from that, due to the irony that you are making a circuit board where most of the main parts have been discontinued for over 30 years. ;)

It did feel funny typing it, but I figure that those interested in making one would have a donor board to use.. It limits the usefulness if one of the new required parts is no longer available.   That said, I wonder if one of those Spartan-3E breakout boards would be feasible to keep it through-hole assembly.

In other news, my Mouser order arrived yesterday, after a 5 day delay.  But My PCBs are nowhere to be found.   They have been sitting at Fedex in China since Monday for some reason.

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7 minutes ago, rkrenicki said:

. . .My PCBs are nowhere to be found.   They have been sitting at Fedex in China since Monday for some reason.

That one is an easy answer, actually. Chinese Customs decided to inspect the package. I've had this happen to three or four circuit card orders over the past ten years--the delay is generally not more than a week, although they held one order for ten days.

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Posted (edited)

i typically order mine shipped via DHL and usually get them in a week from China once they have been shipped.

Edited by Shift838

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1 hour ago, Shift838 said:

i typically order mine shipped via DHL and usually get them in a week from China once they have been shipped.

It's also the delay I have to wait for my PCB orders from China. Sometimes, one or two more days for customs controls.

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Well, the PCBs are now in my state at least.. but they showed up late last night, so I need to wait until Monday for them to deliver.

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On 3/19/2021 at 4:46 PM, rkrenicki said:

That said, I wonder if one of those Spartan-3E breakout boards would be feasible to keep it through-hole assembly.

Do you have any links?  I don't know that I have seen a breakout board for a Spartan-3E, at least not on a realistic size board.  However, if you are literally talking about a break-out for *just* the FPGA, i.e. the required regulators, oscillator, flash, level shifters, etc. are going to be on the main-board, then it would not be too hard or expensive to make just that board.  As soon as you start including other parts on the break-out board, you get into a slippery slope where you end up with something like the MK2.

 

Through-hole parts are going to become obsolete sooner than later.  Many manufactures are producing parts only in SMD packages now, and the through-hole stuff is going to continue to drop off.  I'm running into this even with the SMD parts, where a chip I'm looking at is only offered in the CS (chip-scale) or WL (wafer-level) package, and all the smaller FPGAs are BGA-only now with 0.5mm or *smaller* pitch.  Such a PITA for assembly, and the hobbyist-level PCB capabilities are not where we can route these parts yet (need the 3mil trace/space and micro-vias for those kinds of parts).

 

BGAs aside, IMO, most SMD is not that much more difficult to work with than through-hole, and people's resistance to SMD is simply more of a resistance to change.  If you take one step back from through-hole, you could say having a project that requires soldering "at all" is a no-go for some people (probably more of those people than the ones who think they can't solder SMD parts).

 

I never did SMD before the F18A project, but now it is old-hat.  The 0603 and larger parts are pretty doable by hand with some basic tools.  Anyway, these are just my opinions and only meant to be food for thought, sharing experiences, etc..  Your project goals are your own to set as you see fit. :)

 

On 3/19/2021 at 4:46 PM, rkrenicki said:

... but I figure that those interested in making one would have a donor board to use. ...

Ooph.  Desoldering parts from those old boards, and keeping the original ICs intact and not damaging the insides (i.e. too much heat during removal), *now* you are talking about something that is really difficult.

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Posted (edited)

I was thinking something along the lines of this: https://www.ebay.com/itm/261136091021.   I have not looked into it for actual usability, but it does seem to be small enough.

 

Going "all new" was never part of my plans. If we were talking about a complete board replacement of fully new parts I would probably just make a DE10-Nano "breakout" to put a MiSTer into a TI99/4A shell with all of the ports.

In other news, the PCBs were delivered today.   I am feeling a bit under the weather today, so I will assemble my first smoke-test board sometime in the next few days.   I do know that the mounting holes are oversized, but that was intended on this version.   I need to find my case to see how it will fit, but I am not entirely sure where I put it.

 

20210322_165113847_iOS.thumb.jpg.76c999f421426ef74c892329291d97d9.jpg

Edited by rkrenicki
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The price is pretty nice, but the QFP208 is just way overkill for the 14-ish I/O you need to replace the 9918A.  It is also a pretty large board with giant 0.1" headers, and it will be really tall and might not fit very well height-wise.

 

When I first started the F18A, I never wanted to make my own PCB; I was trying to just get it done as quickly, cheaply, and with the minimum amount of effort as possible.  But, not finding anything suitable, I had to make my own.  To me that board you linked is an example of being overkill for a specific project, yet still lacking critical parts like the level shifters which would have to go on the main-board.

 

Yeah, I never suspected you were going for an "all new parts" kind of board/build, and I was not really trying to suggest that.  Just staying with the idea of maybe putting the F18A directly on the board, the area around where the original 9918A was would be the only SMD parts.  If you wanted to get an FPGA "breakout" to go in a socket, then you are basically back to the F18A, IMO.

 

The boards look pretty good too.

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Well... One way to go... If it does not fit in the real TI, is to make a PEB! A modern one! So you continue to make your updated motherboard with some upgrades AND a connection pin/cable to the "Modern PEB" with all the "bells and whistles" in THAT. Then you can go totally mad, in the "Modern PEB".

So you make an upgraded motherboard that fits the real TI and make all the preparations for one "big" connection to the "Modern PEB". Then all the different modern additions could be connected to ONE big modern PEB.

Me personally, I think that 2) is the way. If it all fits in the real TI. BUT if possible... add 2-4 connections to TV/monitor. Normal plug, Scart, RGB, DVI and HDMI cable. Then all you need is the real TI and (the dream) an HDMI cable, and you can take the TI with you and have fun with other people in their home on "standard" TV/monitor.

And maybe wireless joystick option!

And, thinking of wireless, that is an option to make a "cable" that makes the system more flexible. If at all possible to make a wireless connection directly to the motherboard as an upgrade.

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Using a direct HDMI out from this type of hobby board is probably never going to happen. It is very possible from a technical standpoint--and unbelievably expensive from a licensing standpoint. That is one of the issues that caused serious delays in the new F18A boards--there are no hobby exceptions in the licensing standard, which basically forced Matt into a complete board redesign to eliminate potential issues. Read the Mark II development thread to see all of the gyrations there.

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44 minutes ago, Ksarul said:

Using a direct HDMI out from this type of hobby board is probably never going to happen. It is very possible from a technical standpoint--and unbelievably expensive from a licensing standpoint. That is one of the issues that caused serious delays in the new F18A boards--there are no hobby exceptions in the licensing standard, which basically forced Matt into a complete board redesign to eliminate potential issues. Read the Mark II development thread to see all of the gyrations there.

Then what IS possible ;)

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1 hour ago, oddemann said:

Then what IS possible ;)

Buy the mark II that Matthew is working on developing or use the design files and recreate the f18a, then use a vga to HDMI converter. Then you can still take that ti to other people's houses and game play....😊😊

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Posted (edited)

So let's not hijack this thread with the (H) (D) (M) (I) topic (yes, I am allergic to the term), but here are some basic details AFAIK.  Also keep in mind that the MK2 was almost ready in 2018, so literally *years* have passed and things may have changed. :(

 

* Avoid any kind of use of the term, logo, etc.  Meaning, do not put those four letters together anywhere or claim that kind of named output.

* From what I have read, you can use the connector itself, it is not licensed.  I reacted to quickly on this one, but it was for the better in the end.

* TMDS (transmission minimized differential signaling) used by DVI, and the-other-one we are talking about, is free and open.

* DVI has signaling compatibility, so you can produce DVI and couple it with the connector to get something that will work with pretty much all modern displays and TVs.

* The big difference between DVI and 1.0 of the-other-one is the inclusion of audio data.

* The patents covering the features in the 1.0 spec might be expired or expiring soon.

* A license is $5000/yr for unit quantity under 10,000/yr.  Over 10,000 units and the license is more ($15K IIRC) and you pay a per-unit cost of something like $0.31.

* The founding companies are huge: Philips, Lattice Semi, Maxell, Panasonic, Sony, Technicolor, Toshiba.  They probably don't care about hobby projects (the risk is yours, this is NOT legal advice of any kind).

* V1.3a of the spec is available for free download, with an agreement to their terms.  When I started the MK2, there was no legally-released free spec.

 

Many hobbyist and open source projects go ahead and use the connectors and the name, but it is unclear how many, or if any, of them run into legal trouble.  If they do, it seems the settlements are private and I found it impossible to find any definitive examples and outcomes.  I also think many projects are just producing DVI signaling because it is easier, and they unknowingly avoid any possible legal trouble.  Those that go the extra distance to include audio in the channel signaling don't seem to have any legal problems either, but this is where the waters muddy.

 

At this point it seems there are so many projects out there doing this, it would probably be hard to bring any to court, but that is a risk each person doing such a project has to decide for themselves (I am NOT giving any legal advice here).  The MK2 uses the connector on a separate header and DVI signaling.  Making a header also means the MK2 can produce VGA with a header swap and some settings (will probably require a different bit-stream, but we'll see).

 

Edited by matthew180
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Posted (edited)

I am not married to "the unnameable", but if possible to upgrade to a slightly new picture "cable/system", that would be great. "The unnameable" can be used on monitors and TV... but if there is a license to it, then it is solved - it is not an option!

Then I see 1-3 connection possibility. The original, RCA (audio and picture) and DVI with a separate output for sound. So if it came with DVI, it would be great.

As this is in the start, I dream big when I put out my ideas. I know that some of my dreams are just that. Like "the unnameable", because of the licensing. Great, no need to think more about it. Me, I see a motherboard and that there are possibilities now, to think, dream and maybe make a great update. I have 3 real TI. My first that I could move all my chips over to something like this. So I put out stuff and maybe NOTING is cool, maybe something is. I think that different points of view will give more options that maybe the maker is not thinking of. So as this is new and open, it has many possibilities. And maybe it will spark a greater idea in the maker ;) of this.

Like wireless... Wireless sound? Wireless internet? Wireless joystick? Bluetooth? This then can be another way to connect the Raspberry pi, maybe. With wireless, it becomes (in my mind more flexible for future stuff). lol an app on the android to work as a disk :p hehehe I don't know if it is even possible :p I just dream. But I think if one had a wireless connection to the TI, one could do stuff more "clean".

Maybe "fix" the joystick port, so that one can use the type that all other systems can. And two ports?

So... if I think about stuff that is crazy lol, my knowledge of the TI is limited. This kind of project is light-years from my capability and understanding. I have a basic understanding, and for sure do I know about all the limitations of it. I barely get around Ex B :p hehehe But... I can dream :p

PS! Furthermore, I was viewing a YouTube by a guy about the computer on the moon-lander. This is before the TI, and it was impressing what they were able to squish out of something old then the TI. (Light Years Ahead | The 1969 Apollo Guidance Computer) For me, in my mind the biggest difference is the weight of the computer... from 32 kg to less than 1 kg. And kinda the same computer power as the "modern" TI.
PS!! squish (not the right word, but I like it, and it conveys my idea hehehe)

Edited by oddemann
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Posted (edited)

Let me start of by saying.. I may dream big, but I am not talking about adding Wifi/Bluetooth/etc.    At that point, you might as well just run an emulator on a Raspberry Pi, which is very much "cheating" in my opinion.   Using an FPGA to emulate cycle-accurate versions of old chips is as far as I would be willing to go.   Anything beyond that is beyond the scope of what I am trying to accomplish here.

The only real exception to that would be the video system, since using composite video or Analog RF video is getting harder and harder nowadays.   I am perfectly fine with a potential VGA, but DVI is okay too.

 

 

 



 

Edited by rkrenicki
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3 hours ago, matthew180 said:

So let's not hijack this thread with the (H) (D) (M) (I) topic (yes, I am allergic to the term), but here are some basic details AFAIK.  Also keep in mind that the MK2 was almost ready in 2018, so literally *years* have passed and things may have changed. :(

 

* Avoid any kind of use of the term, logo, etc.  Meaning, do not put those four letters together anywhere or claim that kind of named output.

* From what I have read, you can use the connector itself, it is not licensed.  I reacted to quickly on this one, but it was for the better in the end.

* TMDS (transmission minimized differential signaling) used by DVI, and the-other-one we are talking about, is free and open.

* DVI has signaling compatibility, so you can produce DVI and couple it with the connector to get something that will work with pretty much all modern displays and TVs.

* The big difference between DVI and 1.0 of the-other-one is the inclusion of audio data.

* The patents covering the features in the 1.0 spec might be expired or expiring soon.

* A license is $5000/yr for unit quantity under 10,000/yr.  Over 10,000 units and the license is more ($15K IIRC) and you pay a per-unit cost of something like $0.31.

* The founding companies are huge: Philips, Lattice Semi, Maxell, Panasonic, Sony, Technicolor, Toshiba.  They probably don't care about hobby projects (the risk is yours, this is NOT legal advice of any kind).

* V1.3a of the spec is available for free download, with an agreement to their terms.  When I started the MK2, there was no legally-released free spec.

 

Many hobbyist and open source projects go ahead and use the connectors and the name, but it is unclear how many, or if any, of them run into legal trouble.  If they do, it seems the settlements are private and I found it impossible to find any definitive examples and outcomes.  I also think many projects are just producing DVI signaling because it is easier, and they unknowingly avoid any possible legal trouble.  Those that go the extra distance to include audio in the channel signaling don't seem to have any legal problems either, but this is where the waters muddy.

 

At this point it seems there are so many projects out there doing this, it would probably be hard to bring any to court, but that is a risk each person doing such a project has to decide for themselves (I am NOT giving any legal advice here).  The MK2 uses the connector on a separate header and DVI signaling.  Making a header also means the MK2 can produce VGA with a header swap and some settings (will probably require a different bit-stream, but we'll see).

 

But... If I understand correctly... you have fixed this problem ;)

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21 hours ago, rkrenicki said:

In other news, the PCBs were delivered today.   I am feeling a bit under the weather today, so I will assemble my first smoke-test board sometime in the next few days.   I do know that the mounting holes are oversized, but that was intended on this version.   I need to find my case to see how it will fit, but I am not entirely sure where I put it.

 

20210322_165113847_iOS.thumb.jpg.76c999f421426ef74c892329291d97d9.jpg

Nice work ! Have a lot of fun assembling the motherboard 🙂

 

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Posted (edited)
On 3/22/2021 at 6:23 PM, rkrenicki said:

20210322_165113847_iOS.thumb.jpg.76c999f421426ef74c892329291d97d9.jpg

Hmm, wonder if you've noticed that there are a couple "parts discrepancies" between the schematics and the assembled boards:roll:...

 

 

Looks like you went with the schematic's description. I've wondered which of the two are correct myself.:twisted:

Perhaps there are other examples as well?:ponder:

Edited by HOME AUTOMATION

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