5 ms·

I'm really curious how they're doing video. That was the big roadblock I hit when making a Z80 computer a while ago (and what led me to FPGAs).

LeonM 7y ago
The photo is low res, so can't say for sure, but I expect it uses a microcontroller of some sorts to generate a composite video output.
- randrews 7y ago
  That's a lot harder than it seems, so, I have my doubts. It needs to not only run fast enough to bit-bang the signal but also simultaneously respond to bus requests from the 6502.
  - duskwuff 7y ago
    The microcontroller doesn't go on the 6502 memory bus. If data is sent to the microcontroller over a serial channel (e.g, SPI or UART), it can handle incoming data during blanking periods.
  - phaedrus 7y ago
    All depends on which microcontroller it is using. The Propeller microcontroller has multiple cores and specialized registers for video, so it can just dedicate independent core to video and bus control. An Arduino is certainly fast enough to bit bang video, and it could probably interleave bus control between servicing pixels, but the code and timing for that would get complex.
  - deelowe 7y ago
    There's no graphical display on the apple I. You just need the atmel to handle the big banging. The rest is uart and there's quite a number of PAL and NTSC composite libraries out there that can do this for arduino.
- sergpanarin 7y ago
  Yep, I use ATMega as a videocontroller. You could drop me a line and I’ll give you a pice of advice for your project
stevekemp 7y ago
Do you have any notes on your build? I'm in the early stages of planning a Z80-based system. I hadn't really considered video, just serial-console I/O. Currently I'm using an arduino to emulate RAM and I/O. I'm at a stage where I can run simple programs, and have a working BASIC interpreter running on the processor. The next step will be wiring up real RAM/ROM, along with serial I/O, making the system completely standalone.
sergpanarin 7y ago
We also made our drivers open-source - here is video driver’s source code that we use. It’s code for Arduino that could be uploaded to Atmel 328P that we use - https://github.com/smartykit/apple1/blob/master/SmartyKitApple1_VideoTerminal/SmartyKitApple1_VideoTerminal.ino https://github.com/smartykit/apple1/blob/master/SmartyKitApp...

LeonM 7y ago

The photo is low res, so can't say for sure, but I expect it uses a microcontroller of some sorts to generate a composite video output.

randrews 7y ago
That's a lot harder than it seems, so, I have my doubts. It needs to not only run fast enough to bit-bang the signal but also simultaneously respond to bus requests from the 6502.
- duskwuff 7y ago
  The microcontroller doesn't go on the 6502 memory bus. If data is sent to the microcontroller over a serial channel (e.g, SPI or UART), it can handle incoming data during blanking periods.
- phaedrus 7y ago
  All depends on which microcontroller it is using. The Propeller microcontroller has multiple cores and specialized registers for video, so it can just dedicate independent core to video and bus control. An Arduino is certainly fast enough to bit bang video, and it could probably interleave bus control between servicing pixels, but the code and timing for that would get complex.
- deelowe 7y ago
  There's no graphical display on the apple I. You just need the atmel to handle the big banging. The rest is uart and there's quite a number of PAL and NTSC composite libraries out there that can do this for arduino.
sergpanarin 7y ago
Yep, I use ATMega as a videocontroller. You could drop me a line and I’ll give you a pice of advice for your project

stevekemp 7y ago

Do you have any notes on your build? I'm in the early stages of planning a Z80-based system. I hadn't really considered video, just serial-console I/O. Currently I'm using an arduino to emulate RAM and I/O. I'm at a stage where I can run simple programs, and have a working BASIC interpreter running on the processor. The next step will be wiring up real RAM/ROM, along with serial I/O, making the system completely standalone.

sergpanarin 7y ago

We also made our drivers open-source - here is video driver’s source code that we use. It’s code for Arduino that could be uploaded to Atmel 328P that we use - https://github.com/smartykit/apple1/blob/master/SmartyKitApple1_VideoTerminal/SmartyKitApple1_VideoTerminal.ino https://github.com/smartykit/apple1/blob/master/SmartyKitApp...