Finally, the design is done

Computer2

After a whole lot of procrastinating, the design of my 6502 single board computer is done. There’s nothing like the relief of clicking on the ratsnest button in Eagle and seeing the words, “nothing to do.”

I’ve updated the schematic and board files in my git and added a zipped gerber folder containing all the files any board house should need to fab this computer.

There are a few extra things I added to the board since the last update. First, I’ve put a silkscreen image of Ada Lovelace underneath the CPU. Also, I’ve put an image of BMO from Adventure Time in the top layer of copper underneath the Molex connector:

BMO

He wants to be a real boy

The final board dimensions are 140.6652 x 67.6402 mm, according to OSH park, where the board will cost $73.70 for three. I’m not too keen on spending that much for something that probably won’t work the first time, so I’m probably going to go with Seeed Studio. That seems to be the cheapest at around $45 for five boards.

As far as the toolchain for developing on this computer goes, after looking around the 6502.org forums I’ve decided to go with this really cool 6502 macro assembler and simulator. While I’m sure this is a competent simulator, I’ll also be verifying ROM images in this 6502 emulator. The Symon emulator includes an emulated ACIA tied to a serial console, but the memory address for the ACAI in Symon and my computer differ. That shouldn’t be too hard to code around.

I’ve also started work on my first ‘shield’ for this computer. It’s basically four octal buffers tied to each of the VIA I/O ports. Each of the outputs on the buffers will be tied to a LED. It’s an easy way to verify that everything is working.

buffer

Now it’s just an issue of waiting a month until the SBC board arrives from a month-long trip from China. Just as well, though. I’ve got a lot of writing to catch up on, and now that I’m not designing a computer from scratch I probably won’t be as distracted (ha!).

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