Gigatron Hackers

I didn't even know they used diodes. The way I work out the resistor values to use is to write a series of equations based on the Thevenin equivalent circuit with the 75ohm load and solve for the resistor values needed to achieve the target voltages. I'd have to go dig up my circuit analysis textboo...

I'm also leaning towards the level shifter messing with the VGA timing or levels. I question what that RC circuit he's introduced on the VDDA rail would do to output. A scope capture of the SYNC pulses comparing the input and output levels would be instructive. TBH I really don't have a lot of exper...

For some reason, I could not get an image out of the VGA connection. HSYNC/VSYNC work, as the controller also works. I looked at his constraints file and both his and the tang nano 9k schematic. He assigned the outputs to a 1.8V bank of pins and is using a 2.2k/4k voltage divider to get the 3.3V sw...

I think it's under the PhilThomas Contrib folder in the GH repo. Also have you seen this? viewtopic.php?t=459

Are you able to tell what IC the knock off controller uses inside? I'm assuming it's hidden under a glob top. If you have the parts handy, it's fairly trivial to build a CD4021B or 74xx165 based NES controller if you want a guarantee of compatibility. https://www.raphnet.net/electronique/arcade_cont...

Nice work Mike! Dude, first Poker then Craps... When are Slots, Roulette and Blackjack going to be released? I'll get started working on the Gigatron Casino setup. Congrats again!

I'm still leaning toward overscan. Most modern TVs I've used have a PC mode that removes all post-processing like scaling, etc. If you don't have that, I'd suggest trying a native 4:3 monitor (not TV) if possible. Something old enough where 640x480 was actually tested! Where I'm at, I've picked up m...

Is that a monitor or TV? If TV, does it have a overscan on/off or PC mode menu setting? Are you using 6.25MHz crystal or something different?

I played around with the DJGPP version of Allegro decades ago for 8-bit graphics on a 486DX2/50 . Might be useful as inspiration for an API, but probably too complicated for what the Gigatron can reasonably handle. https://www.allegro.cc/files/?v=4.2