Project History:
 It's hard to say when I started work on this project, because it was one of the main motivations for me to get started with PIC USB interfacing sometime in the summer of 2006.  Since then I've written a number of articles on the things I've learned, and all of these subjects were ones that I needed in order to do this SDC project the way I wanted to.  It wasn't until probably November or December of 2006 that I got most of the background work out of the way and actually started focused work on the SDC project itself.

Current Progress:

The new main SDC board

Auxiliary board

The core SDC functionality is working.  This is implemented using a state-machine type model, which allows for more expandability and flexibility (from a programming standpoint) for the number of different power states that need to be traversed through in order to achieve the desired power sequencing. 

The USB interface, one of the most important parts of the whole thing, is working.  From my C# .NET 2.0 application, I can send commands to the SDC, receive its responses, and the SDC can asynchronously send messages to the computer application as well.  I have been successful in getting the C# program to order the PC to shut down, stand by, hibernate, etc.  

The SDC currently sends information about its status any time something changes - this can include any level of status information: as brief as a few flags indicating its current mode and any important errors, or as complex as monitored parameters like voltage, temperature, digital I/O, etc.  The software can successfully both read and write all the various delay values on the SDC, allowing them to be adjusted easily from the PC.  All delay values and settings on the SDC are stored in non-volatile EEPROM memory, and are thus maintained even when power is removed.

Currently the SDC is configured to monitor several analog input channels, out of the possible 12 that are on the 18F4550.  These are hooked to various things, particularly the input (battery) voltage, 5v and 12v rails.  There are still 5 channels available, broken out to solder pads for later use.

The I²C interface between the 18F4550 (SDC board) and a 16F88 (auxiliary board) is working, enough to send packets in either direction.  Due to the Master-Slave nature of the I²C bus, extra work was required to achieve a semi-asynchronous communication between the boards in a moderately efficient manner, but has resulted in a flexible protocol that keeps the Auxiliary board easily expandable for future features.

The current auxiliary board consists of a few buttons and a character LCD - enough to use a menu system to change settings, delay times, display monitored parameters, etc.  There are still at least 4 pins available, that can be analog input or digital I/O, the usage of these has not yet been decided - however, given the intended modular nature of the auxiliary board it's somewhat irrelevant as a microcontroller with more I/O pins could just as easily be used.  

The SDC board is still partway between a prototype/development version and a usable version - I didn't add a lot of connectors yet because connectors are expensive, and not necessary for development purposes.  There will be a molex power connector on a short pigtail, to bring in 5v and 12v for monitoring, and also for providing a switched regulated 12v output through the relay.  There are also pin headers for power button, reset, power LED, etc.

Current focus is on increasing the level of control between the PC, SDC, and auxiliary board to achieve the aforementioned functionality goals, as well as adding more of the smaller features.

  {mos_sb_discuss:8}