marcelk wrote: ↑02 Jun 2018, 16:17 I agree that two more shift registers is not nice. The one on the board is already a little cheater. After all, software could easily sample the game controller bits during vertical pulse. The 74HC595 is rather complex because it has 16 flip-flops and a tri-state buffer. We're effectively not using its latching capability, but still, it could have been a 74LS244 as was on the prototype breadboard. [Our excuses for replacing it: more pins, no space, and no motivation at the time to shovel even more into software. We conveniently blamed the complexity on the "modern" game controller .]
Thanks! I also start thinking about key codes and layout. With a full 8x8 Matrix and the shift button bit moved to position [BUS 5] it's possible to build a direct 7-bit Ascii compatible keyboard. This gives us the most minimalistic way to use the actual build in font but I am not sure if this gives us the best possible keyboard layout for the Gigatron with a lot of symbols we don't really need. Maybe we also change some characters in the ASCII Font for simple blocky gfx like on the C64. Maybe we could have some dedicated Gigatron software relatet keys to speed up programming or control hardware or font related stuff...
I am currently trying some 5x8 and 8x8 Layouts. It would be ideal if they are both basically usable with the same interface/"driver" code.
But that would be a separate discussion later at this forum.
Yes, but I am not sure how much users are willing to modifying their hardware? For me it is easy to wire some signals to the DB9 or patch alternative opcodes etc. But I would also prefer to have a most community machines compatible. It would be interesting to start a survey about it.marcelk wrote: ↑02 Jun 2018, 16:17 There is some chip count reduction possible by hooking directly into the Gigatron circuit. I'm looking at the Y register outputs... On the breadboard I had one LED on its unused pin. They are also close to J4, unlike the LEDs. On the receiving end it is not as clear unless by removing the 74HC595 anyway and putting a 74HCT244 back there.
As I saw the Gigatron for the first time I thought I would hack it to the max. But I think the relative big RAM and ROM are made for more complex software. And therefore a compatible system brings more exchangeability and fun thru the active community.
Back to the Gigatron Matrix Keyboard Interface (GMKI): First I'll try to use the available signals on DB9 only. We will see how far this comes. Now I have to setup an Arduino and start learning GCL .