Loki uses a stackable expansion system much like the Arduino and other develoment systems, but it has a couple of novel features to take advantage of this flexibility, the most significant of which is how it handles the pin conflict issue that plagues most stackable systems. Instead of using through-hole headers, each expansion board ('plank') has surface mount headers top and bottom. A plank takes the first IOs on the header for its own use, then reroutes the remaining ones to the first positions on the output header to fill the gap, completely eliminating the issue of pin conflicts between expansion boards. To make using and configuring this easier, each plank also has an I2C EEPROM containing configuration information, allowing the bootloader to print out a pinout table for any set of connected expansions.
Other features include:
- 3.3v level signalling
- High efficiency 5V@1A switching regulator with 6-20V DC input
- 3.3v@300mA low noise linear regulator for logic power
- Onboard USB bootloader
- Programming header allowing you to program and debug the chip directly with a Cypress miniprog3
- Native full speed USB support on-chip
- Onboard microSD slot for extra storage
- NEW: Sick of beige 8049 standard dimensions
- Open hardware, naturally!
I've finished the first draft of the PCB design, and I could really use feedback on the schematic and layout. Since my account is new, the forum won't let me post links, but you can find higher resolution pictures and the full size schematic at the link above.
I'd also like to create a thriving ecosystem of expansion boards for the Loki, so here's the plan: Design an expansion board that others are likely to find useful, release it under an open hardware license, and I'll get some made at my expense. I'll then send you some of the boards, along with a fully built and tested Loki board, for you to experiment with. In the unlikely event this turns into a project with commercial potential, I'll consult with you on selling your expansion, and split any profits with you. Can't ask fairer than that, eh?
The specifications for designing an expansion board are here. The design files for the main Loki board, as well as an Eagle library with a layout for standard and short planks are all available here.
What expansion boards would you like to see?
How is this different from the freeSoC?
It'll be a lot cheaper - around $35-$40 for the basic model. It also has this nifty stacking header system described above.
How is this different from the eZPSoC3?
The chip used has more pins and thus more IOs available, and it's upwards compatible to the PSoC 5. There's also more onboard, including a switching regulator and uSD card slot. And don't forget the neat stackable header system!