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dbuchwald / 6502

DB6502: 65C02 based computer inspired by BE6502
MIT License
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VGA video output #49

Open marcpiulachs opened 4 years ago

marcpiulachs commented 4 years ago

Do you plan to add any kind of video output to the computer? You currently have a ATtiny4313 that is only used for the ps/2 keyboard interface that could probably also be used to generate some rudimentary VGA signal https://hackaday.com/2015/12/17/attiny-does-170x240-vga-with-8-colors/

dbuchwald commented 4 years ago

Hey, thanks for sharing, and yes, I'm aware of the possibility to use ATtiny as VGA signal generator, but there are two issues with it at the moment:

  1. Current solution doesn't provide enough video RAM for any reasonable output (keyboard buffer takes up a lot of memory on ATTiny), so I would need to share system RAM between ATTiny and 6502, and while this is perfectly doable, it requires access to certain 6502 pins that are currently "blocked" (as in: pulled up or down on PCB). This basically requires another revision of PCB and this one might actually be used for it: https://github.com/tonylweil/6502
  2. Even if I ever do any kind of VGA interface, I would rather implement that with much simpler and easier to control set of TTL chips, like the Ben's video card. That being said, I don't have that much interest in VGA signal generation, and I definitely don't want to build any kind of primitive game console. What I wanted this thing to be was educational device that demonstrates basics of computer build and OS development. Serial connection is perfectly sufficient for these purposes...

Again - at some point I might actually consider building discrete, TTL based VGA output, but mostly aimed at text mode. Graphics will be always secondary.

Thanks for showing interest in my project!

marcpiulachs commented 4 years ago

Hi, it makes perfectly sense. Thanks for your great work with this project, it's a great tool for people like me who came from a software background with little experience on hardware that want to learn the basics of a computer and how it works but does not feel confortable with wires and breadboards, also the software is a great complement to Ben's excelent series. Please keep the great work!

dbuchwald commented 4 years ago

Thanks for your comment; it seems that quite a lot of us share the same background in software development and this might be the first serious EE project. It is definitely the first for me :)

And this is exactly where I envisioned this project - to be soft of "no frills" intro to hardware and low level software design, building on top of Ben's introduction to 6502 and computer prototyping.

kyleeddy commented 2 years ago

Not VGA, but definitely authentic - I've had some initial luck using the TMS9918a board designed by @jblang. Connection uses pins available on the J7 connect of your v001 board. The board is designed to work with the rc2014-style systems, but works well with some creative use of the jumpers and an added 74HCT04 for timing delays.

Alex-Kw commented 1 year ago

Not VGA, but definitely authentic - I've had some initial luck using the TMS9918a board designed by @jblang. Connection uses pins available on the J7 connect of your v001 board. The board is designed to work with the rc2014-style systems, but works well with some creative use of the jumpers and an added 74HCT04 for timing delays.

If we are mentioning the RC2014, there is an HDMI and Composite Pi terminal, and a VGA terminal. The latter is more relevant here and more available anyway. I have the HDMI one, and it connects to the serial bus; I have TX and RX split so that input comes from a serial device, but output goes to the video terminal. It's likely this could be adapted for many microcomputers with serial text output. https://rc2014.co.uk/modules/pi-pico-vga-terminal/

If I get a chance to try it i will report back, as I intend to obtain one for my RC2014 anyway.