6502.org

I was needing a general-purpose 6502 system that I could get up and running with minimal thought needed on system architecture or software, so I went with an Apple 1 clone!

It's based on the Apple 1 Mini circuit, but I went with an RC2014 backplane (but not RC2014 compatible) to allow me to extend the hardware with add-ons, and I also threw in a thermal printer for output which can be enabled or disabled by sending ASCII control codes to the output PIA.

My first expansion card so far is a 6522 with both ports exposed to the rear of the case on IDC headers. This is going to help a lot with some future projects I have planned...

It's shown here working with my all-in-one Raspberry Pi system as the terminal. All wire wrap construction, and I only found 1 missing wire before I was able to get it all working.

Very cool build! We've got an [link=http://forum.6502.org/viewtopic.php?f=4&t=6730]ongoing thread[/link] about how to assign pins on a 40-pin backplane for 6502 builds. If you're interested in sharing pinouts, you may have figured out something we haven't yet!

I have a similar thermal printer that I want to interface some day, though I was probably going to use an ACIA. Would be interested to hear more about how you have the printer connected to your PIA...

Thank you! I'd love to say that the backplane was carefully planned out, but it's largely just the RC2014 pinout for address and data, and then matched the others as close as possible. It's not intended to be compatible with anything else that's out there. Currently ticks over just find at 1 Mhz but at some point I'll try a faster oscillator in there. I've attached my pinout for ref anyway (excuse my handwritten notes).

The printer is actually attached to the Arduino (well, barebones ATMega328) with SoftwareSerial library to get a second serial port. I just modified Ruud van Falier's sketch with a few lines to listen for ASCII code DC1 to turn enable, and DC3 to disable sending characters to the printer. Those codes are based on the same ones used by Epson in their old dot matrix printers. I'd share the new sketch but there's no license attached to the original so I don't want to just go posting without permission.

Ah, very nice. I remember doing a lot with the Aim-65 and it's little printer. Are you using it for anything specific or just a fun little project?

Cheers,

-Gordon

I'm working on a couple 6502 projects that are essentially embedded* (they use a discrete 6502 but there's no general keyboard/monitor for developing on), so was needing a system that I could use to develop the hardware with, hence the backplane for expansion.

Printer was really just "because I can!", but it's already been useful to just quickly print out and annotate sections of memory for reference.

*turnkey is probably a better word

Was there any particular reason for moving some of the signals that already existed on the RC6502 bus, or was it just something you weren't bothered to try to match up? (I ask in case there's anything you came across that we should be considering when tweaking the RC6502 bus.)

I like the printer. It's also a nice example of how it can be handy to have the serial console TX and RX lines on the bus: you can add additional output devices that listen in and, possibly, additional input devices (such as a keyboard), if you're willing to avoid sending input from two places at the same time so they don't stomp on each other.

Sadly not, no! Compatibility was never a target so I went with a layout that worked well with what the Apple 1 mini already used and kept pins grouped somewhat logically.

That looks amazing! I love designs like that.