About four years ago I designed my first SBC, the COLE-1. It was a pretty basic build: 4 MHz 65c02, 32k RAM, 32k ROM (minus a 2K I/O window), a single VIA, and a 6850 ACIA at 115.2k bps. I had a lot of fun building it, and it helped me get my feet wet, but I really wanted a 65816-based system. The planned successor, COLE-2, got built out on breadboard a couple of times, but I ended up scrapping the design and starting from scratch.

Anyhow, as part of planning my next '816 design, I found myself using COLE-1 to test out various ideas using its VIA ports. Eventually I started thinking about fixing up the original design and having new boards made, to make my main project go faster. Last week I finally sat down and spent a few hours updating the design and laying out a new board. This is the result:



I call it COLE-1+. It has a few improvements over its predecessor:

* The CPU is now a 65816, clocked at 3.6864 MHz (oscillator shared with the ACIA)
* All of the glue logic has been replaced by a single 22V10D GAL
* Added a large decoupling capacitor across the power supply
* Added mounting holes
* Added some silkscreen labels on the expansion headers

This is the barest bones 65816 design I've created; there is no data bus buffer, no bank address latch, and no flip flop on the oscillator. I wasn't sure it was going to even run but I decided to just YOLO it, because boards are cheap and I wasn't buying any new parts for this.

Since this design was pretty simple, I decided to try my hand at using FreeRouting. I tweaked the result by hand to correct some silly decisions it made (mostly choosing to use vias to connect caps to power or ground instead of hooking to nearby pins on that net) but otherwise it did a good job.

Aside from having to add 1 resistor and 1 bodge wire the first run boards work perfectly, both with its original firmware and a modified COLE-2 firmware. However, I may do another layout at some point to correct the errors and add a power switch and maybe a DC input jack instead of USB power.

The black solder mask is courtesy of JLCPCB. It didn't even cost me extra and only added a couple of days to the fab time. Total cost delivered for 5 of these 4-layer boards was a hair under $21.

Looks great!

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Cheers
Troy

[My introduction]

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x86?  We ain't got no x86.  We don't NEED no stinking x86!