I'm planning to do a project with an arduino controller and it's my first one. Before to buy an arduino I want to be certain of something with the arduino mini. When the program is running, and the mini is on communication with another serial device or waiting for it, how I can download the program for an update.
If the other device sends data while you're downloading a program it will mess things up.
What you need is an ISP programmer. This bypasses the Arduino bootloader and serial port. You can easily get one for under $15. I got mine on eBay for $12.
Is the reset button must be pushed and right after I can download on it....
Arduinos have auto-reset, no need to push any buttons.