usb serial connection after reattach to host

Is it possible to keep the serial monitor alive (and its connection) even if the arduino turned off and on again?

Scenario:
For my application the sleep mode consumes still to much energy (the board is powered by external 12V source). Therefor I have build a circuit (with tyhristor and transistors) to cut off power completely on pulse (output pin high) and reconnect power on other pulse (vibration sensor).
During development and debugging I need the usb-serial connection at once. To test the turn off and on behavior I cut the +5V lead of usb cable.
The problem:
When arduino turned off and on (from host side this must be like detach and reattach the usb device) I have to restart the serial monitor to reconnect. During reconnect the serial monitor the arduino resets to top it all. Therefor I have found Arduino Playground - DisablingAutoResetOnSerialConnection but this solves not the whole problem i think.

Additional information:
I use arduino uno rev.3 and mac os x for developing. But i also could use windows or linux if this should be the problem.

Thanks a lot for helping.

You're disconnecting then reconnecting a USB device so it will reset in the OS device list.

To keep it alive you'd have to use an FTDI adaptor to move the USB device off the Arduino. The FTDI chip will remain powered on, the connection will stay alive.

That sounds plausible.

Is it possible to modify the board to supply only the ATmega16U2 (thats used instead of a FTDI chip on uno) with power over USB to keep usb connection alive - and disable power supply via usb to the rest of the board?

Otherwise:
How can I use an extern FTDI chip with an arduino uno?

jojoob:
Otherwise:
How can I use an extern FTDI chip with an arduino uno?

fungus:

jojoob:
Otherwise:
How can I use an extern FTDI chip with an arduino uno?

Diavolino

But this is a "Diavolino" and no Uno. ]:slight_smile: Thank you anyway :wink:
I would be reluctant to change to this board because I need support for the antrax gps/gsm shield and would miss the onboard voltage regulator to power the arduino with 12V.

jojoob:
But this is a "Diavolino" and no Uno. ]:slight_smile: Thank you anyway :wink:

It's 100% compatible, it just removes the USB-to-serial and power circuitry. Your shield will work.

jojoob:
I would be reluctant to change to this board because I need support for the antrax gps/gsm shield and would miss the onboard voltage regulator to power the arduino with 12V.

A 5V regulator costs about 30 cents, eg. LM7805.