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Hey,

 

does anyone have experience with building an F18A from the design files at CircuitMaker?  The soldering job seems doable, but is this the latest version and will it run with the firmware published on Matthew's site?

 

Thanks,

Hans

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The firmware ZIP file contains the .MCS file with the FPGA bitstream.  I'm not actually intending to change the VHDL at this point, just building and using an F18A would be alright for me.

 

Any experience reports would be appreciated.

 

-Hans

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26 minutes ago, Hans23 said:

The firmware ZIP file contains the .MCS file with the FPGA bitstream.  I'm not actually intending to change the VHDL at this point, just building and using an F18A would be alright for me.

 

Any experience reports would be appreciated.

 

-Hans

Nice find! I don't think anyone in the community was aware this was released as a full package. 

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I've ordered 10 PCB's and will give it a try.  I'll let y'all know whether I get anywhere with it.

 

-Hans

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7 hours ago, retroclouds said:

Nice find! I don't think anyone in the community was aware this was released as a full package. 

That's how all the upgraders worked, too. ;)

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Any progress to report?  I have been waiting years to be able to purchase an F18A or mk2.   If this works out, I would consider the DIY route.  
 

Brent

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Hi folks,

 

glad you asked, here is a short(ish) report on my progress on building F18A's from the design files on CircuitMaker.com.

 

TLDR; I'm about to test my first DY F18A in a TI-99/4A, but I need to get into the mood.

 

Getting the PCBs made was the easy part, and I have ordered 10 just for good measure.  When the boards arrived, I found that a track was missing in the layout, visibly.  The track was to one of the enable pins of a voltage regulator and the schematics called for it to be there, so I went for a patch:

 

20210210_231746.thumb.jpg.22a47ab14bcd295a530d8005887605fc.jpg

 

Sourcing the chips was a bit more challenging.  The F18A uses the venerable Spartan-3E FPGA XC3S250E, which is pretty old and EOLed by Xilinx.  Some dealers still have stock, but prices are going up - This is one of the reasons why Matthew Haggerty does not produce the original F18A anymore, so I hear.  Anyway, I got three chips from Mouser at €16.70 apiece, and another five from Aliexpress at €7.20 each.  When the Mouser chips arrived in early January, I built the first board, but I realised that I needed a 2mm pitch connector for the JTAG programming.  I ordered from Arrow, which is usually fast, but this time, the parts went on an Odyssey through the USA and Europe before they finally arrived 2 weeks ago.

 

20210210_231759.thumb.jpg.d2cf851e15cc4290d16b0e30b10d7343.jpg

 

With the JTAG connector soldered in, I went to programming the Flash chip that holds the FPGA configuration.  This went smoothly, albeit the Xilinx FPGA ISE design software that is required to program these ancient chips does not run in Windows 10, and requires the installation of a virtual machine with ISE running under Linux.  For some reason, access to the USB programming cable is very slow from the VM, but eventually I succeeded to get the Flash programmed.

 

Unfortunately, the first board that I built drew way too much power after I had programmed it - I don't really know how much current an idle and out-of-circuit F18A needs, but 600 mA seemed way too much to me.  As I made some mistake orienting the Flash chip, I suspected that I might have damaged the FPGA, put the first board to the side and built a second one.  Other projects came up and I did not make progress after putting on the initial parts, but a few days ago, the Aliexpress chips arrived and that put me under pressure to test them in order to get a refund if they don't work.  Thus, I built a second board last weekend - Programming the Flash went slowly but smoothly, power consumption is much more reasonable at 150 mA, and now the board is sitting on my bench waiting to be tested in a TI-99/4A.

 

20210210_231728.thumb.jpg.a0202f6e69d255f64099e44d0995c99b.jpg

 

20210210_231825.thumb.jpg.8c4a68c8982abb11aed4796194414d4e.jpg

 

Before I can go ahead, I will have to solder a VGA cable, but I have everything in stock for that.  Thus, I will be able to report whether this whole effort actually leads anywhere this weekend, and I'll report.  If it does, I have parts to build another 5 boards which I'll then gladly pass on.

 

I tried getting in touch with Matthew to gather his input on the futility of this, but he did not respond, and I'm at the bottom of the rabbit hole now anyway :)

 

Cheers,

Hans

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Interesting, I have a real F18A which is also labelled as Rev 1.3 but has the missing track.

There are also additional unpopulated parts over in the space on the left.

So these gerbers obviously aren't for the final V1.3 version of the board.

I wonder what other mistakes there are on it....

 

 

 

Genuine F18A rev 1.3 top and botton

2021-02-11 08.48.32.jpg

2021-02-11 08.49.24.jpg

Edited by Jimhearne
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10 hours ago, Hans23 said:

 

 

Unfortunately, the first board that I built drew way too much power after I had programmed it - I don't really know how much current an idle and out-of-circuit F18A needs, but 600 mA seemed way too much to me.  As I made some mistake orienting the Flash chip, I suspected that I might have damaged the FPGA, put the first board to the side and built a second one.  Other projects came up and I did not make progress after putting on the initial parts, but a few days ago, the Aliexpress chips arrived and that put me under pressure to test them in order to get a refund if they don't work.  Thus, I built a second board last weekend - Programming the Flash went slowly but smoothly, power consumption is much more reasonable at 150 mA, and now the board is sitting on my bench waiting to be tested in a TI-99/4A.

 

 

I just measured the current on the real F18a.

Just with the power pins connected to 5v , the current varies a lot with all the other pins floating, in some cases at power up going over the 300ma current limit my psu was set to.

With the F18a sitting on some black conductive foam to stop all the pins floating around then the current is 146ma

 

Jim

 

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Thanks a bunch, @Jimhearne!  Your photos and your measurements will be quite helpful.  I'm going to compare them with my boards.

 

Cheers,

Hans

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No problem, let me know if you need any more measurements.

I don't have a TI-99/4A to put it in but I do have one of Stuarts mini-Cortex boards that takes it. 

 

Jim

 

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6 hours ago, Hans23 said:

Thanks a bunch, @Jimhearne!  Your photos and your measurements will be quite helpful.  I'm going to compare them with my boards.

 

Cheers,

Hans

When do you think you'll put out a sign up sheet for order/pre-order?

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2 minutes ago, GDMike said:

When do you think you'll put out a sign up sheet for order/pre-order?

Let me first see whether the board actually works.  If it does, I'll come up with a way to express your interest.

 

-Hans

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I think you could easily end up with orders for a 200-300 units. 🙂

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I do think you should check that Matthew is ok with you making them and selling for a profit.

I know I wouldn't be happy if somebody took one of my designs and started selling it.

Making a few for your own use is slightly different.

 

Jim

 

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I have no intention to make this into a business.  I want a card or two for myself, and I'm willing to make a few more as I have parts, enjoy building stuff and like making people happy.

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18 hours ago, Hans23 said:

With the JTAG connector soldered in, I went to programming the Flash chip that holds the FPGA configuration.  This went smoothly, albeit the Xilinx FPGA ISE design software that is required to program these ancient chips does not run in Windows 10,

 

...

 

I tried getting in touch with Matthew to gather his input on the futility of this, but he did not respond, and I'm at the bottom of the rabbit hole now anyway :)

Matt's just busy of late, ping him again, or he'll probably find this thread eventually. ;)

 

The Windows 10 thing is interesting. It works fine on my machine (or it did a couple years ago anyway), but not on others. So it's not Windows 10 specifically, but some configuration or component of it. Nobody has worried much about it since the VM exists.

 

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14 minutes ago, Hans23 said:

I have no intention to make this into a business.  I want a card or two for myself, and I'm willing to make a few more as I have parts, enjoy building stuff and like making people happy.

You should get something for your Time. Either way, maybe there's a profitability for Matt regardless, I don't think anyone would mind paying both of you guys for your shared interest.

Just pay Matt a percentage that he asks and let the user/buyer make up the difference. Just don't tell anyone!

Oh... shoot..

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