Disconnecting/Reconnecting Control Interface from Running Engine

For those using netbooks, pdas, computers, or any other peripheral device that consumes power to configure the engine when setting up shots, I thought I'd point out a few tricks that you can use to save power/hassle when in the field:

1) You can always disconnect from the serial interface without issue. That is, once you've configured and started your program, you may simply disconnect the serial interface, and the engine will happily run on its own from there on out.

2) You can not, however, just re-connect the serial interface. Re-connecting trips the auto-reset on the arduino board. The auto-reset is essential for re-programming the board without having to press the reset button on the board. It does cause problems w/ reconnecting a serial interface though. There is an easy solution, however:

2.a) You can simply place a 120 Ohm resistor between the RESET and 5V pins on the Arduino, this will prevent the reset line from ever being pulled low. Then, you can just remove the resistor when re-programming the board.

2.b) Same concept, but use an SPST switch to switch between GND and the 120 Ohm resistor->5v. This way, you can just flip the switch whenever you want to re-program the board, and not have to open your enclosure.

2.c) Cut the auto-reset trace (duemilanove), or de-solder the auto-reset resistor (diecimilia) - this will always require you to press the reset button on the board when programming, or add a momentary switch tied to reset for programming.

These techniques are discussed on the arduino website here: DisablingAutoResetOnSerialConnection

Once you've done one of these techniques, you may disconnect and re-connect from the engine as often as you like, saving yourself power in the field by letting you shut down your interface when not needed.

Combined with the changes soon to be released in 0.82 of the engine, which provides status report back to an interface, interfaces will be able to re-connect and display exactly where in the program execution the engine is.

!c