I've received some feedback on the original design which
has been incorporated along with an assortment of additions
and general improvements. This revision to the initial
design, dials down the layout rules and frees up considerable
real estate. Other changes/additions of note are:
- Addition of an Atmel ATtiny2313 serving as a non-volatile
boot pull controller, remote console switch, remote boot,
system config, IR remote decode, standby/power-on control.
- A PCA9535/9 I2C parallel I/O expander driven by the AVR
to implement the above.
- Addition of a DS1374U battery backed RTC providing the
obvious as well as 3V3 power-on detect reset and
(comically) a source for the 32768Hz 9302 boot clock.
- additional buffering for high address lines as well as
decode of CSn0 space available off-board.
- provisions for a separate standby power rail for the
summary boot controller.
- replacement of the 600ma 3V3 switching regulator with a
slightly more efficient 1500ma controller. This was to
allow daughter cards to be powered from the SBC.
- replacement of the USB 5V0 polyfuse with a power controller
providing over current limit and program power control.
- addition of a Compact Flash socket with power control and
media detect.
- additional buffering for high address lines as well as
decode of CSn0 space available off-board.
- 9302 GPIO F[2,1] are now used additionally as a soft I2C
controller.
- added a TLV320DAC23 I2S/I2C audio receiver which provides
line and headphone outputs.
- INT[3,1,0] converted to negative active wire-OR interrupt
inputs.
- Consumer IR R/C receiver.
- add separate connector for A/D with interleaved grounds.
- replacement where possible of all leaded packages by chip
scale MO-241 package versions.
For the most part the remaining design is the same as the
first version: 2x 16-bit SDRAM, 1x 16-bit StrataFlash, dual
USB host, 10/100 NIC, 2x 50-pin 0.5mm FFC connectors for
IO + CPU bus expansion, and switching regulators for 1V8
and 3V3 rails.
At this point I'm going to do a final sanity check and
ship the works off to a board fab before the 9302 is
out of production. :) There isn't too much daylight
left on the board but comments and suggestions are
welcome. The schematic and PCB output can be found at:
http://groups.yahoo.com/group/linux-widgets/files/
login: linux.widget
pw: w3lcom3
--
uhmgawa wrote:
> Actually I have a 9302 design in which I've used GPL
> tools for both capture and layout.
>
> It has been collecting dust since early last year
> when I let it slide in part due to 2.6 support seeming
> to bog down at the time. Anyway things appear to be
> moving quite well and thus figured I should finally
> tie it off, get a few boards fabed and the works
> vetted.
>
> As is stands it is a fairly simple 3000x5000mil 4
> layer board with the usual complement of 2x sdram,
> flash, usb, async, ethernet, buffered addr+data bus
> along with the balance of 9302 resident I/O available
> for use off the board. My goal was to have a
> generically useful (if somewhat minimal) board by
> itself but be able to add daughter boards of various
> types to include CF/SD/IDE, I2S, USB client, POE, IR,
> and whatever else gets thunk up. But I had a bit of
> a dilemma deciding exactly what to put on the mainboard
> vs. prospective daughter boards.
>
> In order to provide for the possibility of battery
> operation switching regulators were used to generate
> ring and core rails from an assumed main 5v rail.
> Programmable logic devices were avoided to keep the
> barrier to entry low for those who would roll their
> own. There was also the loose goal of an <$50 basic
> BOM cost (in quantity). And of course the design and
> board layout was intended to be available under GPL or
> equivalent.
>
> So I'd like to float a request to folks who may be
> interested in providing a wish list of what in their
> view is a "must have" on the main board and what can
> be deferred to a daughter card. The board is currently
> laid out with less than aggressive designs rules and
> still has some reclaimable real estate so further
> modification is possible. To get a feel where this
> is at, I've parked a recent snapshot here:
>
> http://groups.yahoo.com/group/linux-widgets/files/
>
> login: linux.widget
> pw: w3lcom3
>
> Any and all constructive comments are most welcome.
>
> --
>
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