Modular hardware? Looking for ideas!

[Bruce Frederiksen]

I've been having trouble trying to organize and modularize my microcontroller projects.  After giving it some thought, I had some ideas that I want to start a discussion about.

Basically, the Arduino is designed to have one microcontroller (on the Arduino board) and then have different daughter boards (Arduino calls them "shields") for your different projects.  The shield has the peripherals on it.  When you want to run project X, you plug in the X shield, load the X program into the Arduino and run it.

But keeping track of the programs and having to load and reload the Arduino is a pain in the butt (at least for me, maybe my computer isn't organized enough?).

Also, the peripherals are often more expensive than the microcontroller.

So my idea is to turn this around.  I'd like to hear what you all think of this.

The idea is to build one platform with all of the peripherals on it, and then have a stack of microcontroller boards with the programs permanently loaded on them.  To run project X, you plug microcontroller X into the base platform and you're ready to go.  No program load required.  And you don't wipe out your current project when you want to run an old one.

I'm thinking that the platform could include:

• 5V regulated supply for the electronics
• 30V(?) adjustable switching supply (10A?) for motors, high intensity LEDs, and other power devices
• single plug for power from wall outlet
• several pots, switches and push buttons for input devices
• IR sensor for TV remote input
• several LEDs for output
• also a couple of small displays (maybe 3 digit, 7 segment) for additional output (e.g., multimeter and power supply readings, or output device for plug-in controller)
  
• USB connection to PC
• radio (e.g., XBee) to talk from remote unit to PC or to plug-in controller.
  
• audio generator and speaker
• maybe a microphone (or 2 or 3) and amp
  
• 4+ power transistors with protection diodes, current sense resistors and comparitors where more than 40mA is needed (high power LEDs, unidirectional motor control, unipolar stepper control, etc).  The protection diodes and current sense resistors shouldn't cause any problems for devices that don't need them (e.g., LED) so can be there permanently.
  
• maybe 2 H-bridges for bi-directional motor controller?  Could the 4 transistors in the H-bridge be reconfigured to use seperately (as above), or together as H-bridge?
• 1 or more microcontrollers on the platform orchestrating the I/O.  Use ADC (but faster than Atmel) to do multimeter and storage oscope functions (display oscope on PC).  These would have fixed programs (basically device drivers), and probably I2C interfaces to the plug-in controller (plug-in controller is I2C master).

All of this would be built as one physical unit to make it easy to transport and take to the meetings.

There would probably need to be an easy way to build clip on panels for each project that you can write labels on for all of the switches/buttons/LEDs, etc do for that project.

I'm thinking that this addresses one of three kinds of projects:

1. Projects you run for fun.  You run these on your workbench and show your friends.  This is the type of project that this idea pertains to.
2. Projects that run stand-alone somewhere in the house, powered from the wall, to do a useful function forever.  These probably standardize on 5V for better MOSFET control.
3. Projects that run stand-alone, powered from batteries.  These probably standardize on 3V for lower power and to match two flashlight batteries.

Let me know what you think!

-Bruce