I was gonna ask how to burn bootloader on pro mini, because when I power it up via my USB cable there's a 2 second pause while the green led blinks before my program runs.
And this tutorial for the regular mini says you have to remove the green LED from pin 13: http://www.arduino.cc/en/Hacking/MiniBootloader
And the pro mini has a green led soldered on the board on pin 13 and it would be really inconvenient to remove that.
(Do you need to? I'd still like to know!)
But I just went to plug the pro mini in now, and I failed to plug the usb cable in all the way, and I noticed that it began executing my code immediately instead of waiting, And that's great!
But is there some undocumented feature at work here? Does the pro mini not wait two seconds for code to be uploaded if nothing is done on the Tx or Rx pins, or what? What's going on here exactly, and under what conditions will the Arduino Pro Mini pause before executing code?
It may be worth noting that my plan for some of my projects is to plug the pro mini into a socket, and remove it to program it, so that I can make use of those serial pins. I would be connecting those to ground or to other pins, depending on whether I hook them up to a piezo, a switch, or an led array. So knowing if those would affect the boot time would be very helpful to me.