External power and USB

I use an Arduino Duemilanove board, powered up by an external source.
My sketch stores some data in EEPROM and I want to read them through the USB/serial interface. Nothing complicated.
The problem is, that the program restarts when I plug USB connector to my laptop. I would like it to continue, with the possibility to plug or unplug the USB device. In fact, unplugging USB doesn't trouble the program. It's only when plugging.
I hope it's clear and you have an idea. Sorry for my english...

Here's how I would do it.

If you want to read something, plug it in to the computer and don't plug in external power (that can sometimes cause problems). Then upload a code that does the following:

Read the parts of EEPROM you need, then send it over serial to the computer (or make a program in Processing, etc. that requests specific data). You could then copy the data received, or just make a program that automatically receives it and saves it in a text file, etc. :slight_smile:

I get the impression that OP wants to run the Arduino on external power, with the computer attached. Then, at intervals, connect the computer and retrieve the stored data.

One of the things that connecting the USB cable to the Arduino does is to restart the Arduino. That's what OP is hoping to prevent.

I have no idea how to do that, or if it is even possible.

I have no idea how to do that, or if it is even possible.

There are a few hacks to disable the auto-reset, either by disconnecting the .1mfd cap wired between the FTDI's DTR output signal and the AVR's reset pin, or by installing a lower ohms resistor in parallel with the existing reset pull-up resistor. The seeeduino design uses a manual switch where you can turn on or off the auto reset function.

Lefty