The F18a DIY alternative with HDMI :)

[retrocanada76]

Sharing my latest project I've been working recently:

 

 

[Tighe]

I want at least one of these!!

[Armitage]

Very cool! Subscribing to follow the progress.

[Duewester]

Subscribed. Parts on order for two. Just need the boards files😎.

[retrocanada76]

2 hours ago, Duewester said:

Subscribed. Parts on order for two. Just need the boards files😎.

the gerbers are there:

 

https://github.com/lfantoniosi/tn9k_f18a/tree/main/KiCad/tn9k_f18a/gerber

https://github.com/lfantoniosi/tn9k_f18a/tree/main/KiCad/tn9k_vga/gerber

 

[retrocanada76]

4 minutes ago, retrocanada76 said:

the gerbers are there:

 

https://github.com/lfantoniosi/tn9k_f18a/tree/main/KiCad/tn9k_f18a/gerber

https://github.com/lfantoniosi/tn9k_f18a/tree/main/KiCad/tn9k_vga/gerber

 

just order them black they will match nicely with the Tang which is also black

[Duewester]

@retrocanada76I'm doing this for a Ti/99-4a. Any head's up I should look for?

[retrocanada76]

I don't know about the space. How much room over the TMS9918 on there ? You can reduce the height of the board by using machined female pins on the FGPA board and machined male pins on the board I think this will make it smaller. Then the TMS you connect direct the female machined pins from the board. 

 

[retrocanada76]

and don't socket the 74LVC245, solder them direct to the board.  it will help with the height, you can bring the FPGA closer to the board. Can you take a picture of the TMS and what goes on top like the distance from the mainboard to the keyboard ?

 

[retrocanada76]

also you can solder the FGPA direct to the board, just put some insulation to avoid touching the LVCs under like a piece of kapton tape.

[retrocanada76]

like use these strips the female and the male: https://www.aliexpress.com/item/32892386779.html?spm=a2g0o.cart.0.0.666338dar3Hgaa&mp=1 this will give you a smaller profile. on digikey you are going to pay 7 dollar each, there you get 10

 

[retrocanada76]

@Duewester I was looking into pictures of the TI 99/4a I think the board will hit the case. I need to make a new board with the TMS on top. That would work. I can make a second version and then I will post on the github. I made it for the NABU PC and there is plenty of space. I think it is similar to a CX5MU, my board probably won't fit there.

[retrocanada76]

Actually the orientation on TI 99 is opposite. So I would need to make a squared board, making the FPGA crossing the TMS. It will take few days for that.

[retrocanada76]

would something like this work on a TI99/4A ? Count the number of pins for the TMS, like if it had 5 more pins each side, going towards the RAM portion. Would the case close ? If this won't work I would need to make a crossed and larger version.

 

 

[Switch1995]

99ers are a very active group on Atariage.  I’d be willing to bet anyone with the time/skill/ambition to launch a Go Fund Me for 50 boards at $50 ($15 materials, $35 time) would reach the $2,500 goal quickly.  

[marauder666]

Would this also work on machines which use the TMS9928A(60Hz) or TMS9929A (50Hz) which output something close to component video.  The F18A does work when installed instead of these VDPs.

[Hans23]

34 minutes ago, marauder666 said:

Would this also work on machines which use the TMS9928A(60Hz) or TMS9929A (50Hz) which output something close to component video.  The F18A does work when installed instead of these VDPs.

The code in this solution is the F18A code, and software-wise the TMS9928A and the TMS9929A are identical.  The difference is in clock frequency and output signal.  So to answer your question:  Yes, this board can be used in a TI-99/4A if you get it to fit.  The clearance above the TMS99x8A is much lower than in the NABU PC, however, so the full stack of boards will probably not fit.  Without the RF shield, the second version posted by @retrocanada76 might work, but I'd rather use SMD components to make the stack even smaller - The buffers will fit under the DIL-40 footprint no problem.  It will still be a bit fiddly to get the HDMI cable inside.  Is the VGA output even all that useful if there is HDMI?

[retrocanada76]

yes the jumpers for cpuclk and gromclk are there. Check these dimensions, unfortunately i don't have a ti 99 4/a:

 

 

and yes we can go SMD. The HDMI pins could be pulled and a hdmi breakout board could be made.

 

[retrocanada76]

the kicad files are in the github, if you have on ti 99 4/a i guess it would be easier for you to make a board, then you can add to the project: https://github.com/lfantoniosi/tn9k_f18a

[Hans23]

I'd use 74LCX16245 as buffer chips like on the original F18A - They're easy to find and the TSSOP-48 footprint fits into the DIL-40 footprint.  I'd also make the config jumpers into solder jumpers on the PCB underside rather real jumpers as the configuration of the board is typically not changed after it has been installed once.  Let me know if you don't want to KiCAD this and I'll give it a shot.

[Duewester]

Maybe I should have ordered more parts.🤔

I have a Frankennine (beige 99) with a homemade keyboard I'm not afraid of modding to see if either fits. 

I knew going in that this was designed with the Nabu in mind and would probably have headroom issues.

[retrocanada76]

53 minutes ago, Hans23 said:

I'd use 74LCX16245 as buffer chips like on the original F18A - They're easy to find and the TSSOP-48 footprint fits into the DIL-40 footprint.  I'd also make the config jumpers into solder jumpers on the PCB underside rather real jumpers as the configuration of the board is typically not changed after it has been installed once.  Let me know if you don't want to KiCAD this and I'll give it a shot.

but then you need what an AND port for the CSR CSW -> OE line ? On TTH an AND port would be large as another LVC245 i just added a read and a write LVC245. If you wan't to make your SMD design go ahead it would be interesting to see. I was thinking in using 3x TSOP-2. For the VGA connector, maybe use the same as the MK1 ?

[Hans23]

For a single AND gate, the NC7SZ08M5X as used on the original F18A will do just fine.  The VGA connector used on the MK1 would be an option.  I'll give it a shot over the next few days.

[retrocanada76]

just saw you comments on the German classic computing about creating a F18A using a Tang Nano 9K. Nice. Yes, the Nano 4K is not enough. It does not have enough block ram.

[JasonE]

Subscribed. I have a few Coleco's and Nabu's here lacking F18A. Excellent work!