Today I'm introducing Agon light ORIGINS edition™, the new revision of the original Agon light™ board. Heber Ltd.'s Agon Console8 is already based on the improvements of this new revision. The new board is 100% backward compatible and does not add extra capabilities. So why did I do it?
The original Agon light™ board was essentially a prototype that worked so well we released it. However, over the months, as I contemplated the old board, I found a number of things I could do better: better routing, better layer stack, a couple of better parts. So I figured I would re-do the board, but this time making every effort to get every last bit of electrical performance out of it. I wanted the design to be beyond textbook-good. It felt a bit like cutting and polishing a gemstone; a delight to do. The result was so gratifying that I even ordered gold-plated boards to do justice to the elegance of the design.
The ORIGINS edition excels in signal integrity and robustness; this thing will work stably even under quite adverse environmental conditions. And it looks great too!
At the same time, the ORIGINS edition deliberately preserves some of the quirks of the original design so to honor it, such as a large USB socket for power and firmware programming, a real PS/2 connector for the keyboard, a linear through-hole LDO regulator, and two through-hole electrolytic capacitors.
These are the improvements with respect to the original Agon light™:
- Highly optimized routing, significantly reducing the number of VIA hops, direction changes and trace lengths;
- Optimized layer stack, with GND copper fill on top (the original had Vcc fill on top for heat dissipation, but that wasn't needed);
- Fewer and larger stitching VIAs;
- In-line resistor bank (33Ω) on the data bus to absorb reflections;
- USB-B power/firmware upload connector (instead of the non-standard USB-A of the earlier revision);
- Shrouded control port connector (eliminating the need for TVS diodes).
To give you an example of the refinement of the routing, here are the top and bottom routed layers. Notice how short the traces are, how few VIA hops they require, and how few changes of direction are entailed. It really is a clean, elegant design.
I understand that Olimex plans to carry the ORIGINS edition, so you can get ready-to-use units from them. Otherwise, you can download all the files from the repository. You can then use the Gerber set to make or order your own boards, choosing board thickness, finish and solder mask as you wish. In the photos you see here, I used 1 mm total board thickness (to maximize the distributed capacitance created by the inner Vcc and GND planes), gold finish (1 Oz), 1 Oz metal thickness in all four layers, and black solder mask.
The main Agon website has been updated with the ORIGINS edition.
Have fun!