Sidequest: VGA scan doubler

[PhilC]

looks pretty good to me @Smonson

[Steve]

Very very cool! Good work!

[DoG]

Awesome work!

[Icky]

Great work @Smonson. That FPGA looks pretty easy to solder. Do I spy a Phoenix mug on your desk :)

[Smonson]

Great work @Smonson. That FPGA looks pretty easy to solder.

Thanks @Icky, @DoG, @Steve, and @PhilC :)

The main thing I don't like about that QFN is that it has a "pin 49" directly on the bottom (covering the whole thing). My concern was that if there was too little solder in there it wouldn't stick and if there was too much, it would hold the IC off the board and prevent the other pins from touching. I put some vias in there as a way for extra solder to escape, probably didn't do anything though. After coming out of the oven there was squeeze-out all around the sides so I went over it with a 45-degree bevel tip and that cleaned it up nicely. I specifically left space around the device for this reason after putting the bypass caps too close to get an iron in there on previous boards. So I think that was a good lesson learned.

Do I spy a Phoenix mug on your desk

Product placement! :D

[Smonson]

Added displaying an image on boot. It stays on the screen for five seconds and then disappears. This is pushing the limits of how fast this chip can go unfortunately, so I might struggle to keep this in the build depending on whether I can squeeze a little bit of extra propagation delay out of it. These ICE40s are ancient technology as far as FPGAs go, I've had to do a bunch of extra work to speed things up just to get it to run at 32MHz.

Also I realised that this board isn't driving the middle bit of red, so sorry about any dodgy colours in the last few screenshots. It does make the green desktop look extra revolting :)

v06-lo-boot2.jpg

[Smonson]

Actually I just compared this one that I used (UP5K) with the HK1K family, and it's waaaaaay faster. 32ns vs 12ns maximum delay (30MHz vs 80MHz). It's cheaper, but with the downside of being five times the board area. Probably a worthwhile trade-off because faster propagation equals better picture quality. I will definitely do an experimental board layout for this.

[unseenmenace]

This is fantastic work, thanks for the link @Smonson. If you ever get to the point that you're considering getting a batch made I'd be more than happy to pre-order one!

[Smonson]

This is fantastic work, thanks for the link @Smonson. If you ever get to the point that you're considering getting a batch made I'd be more than happy to pre-order one!

Thanks! Yeah Christmas is a time of broke-ness but I'm going to do a new prototype soon - within the next couple of months - with the HX1K on it which should give it a bit more "breathing room". Bear in mind that this mod does involve cutting a track (easily repairable) on the ST main board.

[Smonson]

I've mocked up the next prototype board in preparation for ordering.

scandoubler_0.7.jpg

I stuck all the decoupling capacitors for the FPGA on the bottom side this time (there's about 8)... time will tell if that turns out to be a terrible mistake.