At reset this boot loader will give a short help text. Then it will wait 3-6 seconds for the user to cancel auto boot.
Auto boot is canceled by pressing ESC exactly 5 times during the 3 seconds, this to avoid entering download mode due to noise or other input.
In download mode it will expect an application to be sent using xmodem.
I have reused code from some other projects found at avrfreaks.net, adapted it for atmega328, added the auto boot part and a little bit of documentation.
Tested on atmega328.
Some more documentation:
doc
A test application (that can be loaded with habl):
helloworld.zip (version 0.1)
helloworld.tar.gz (version 0.2)
www.eit.se/habl/helloworld/0.7
Adapter/converter from TTL to USB uart:
www.eit.se/opto_usb_uart
Older versions of habl:
www.eit.se/habl/1.1
www.eit.se/habl/1.4
www.eit.se/habl/1.5
www.eit.se/habl/1.7
www.eit.se/habl/1.9
Contact information (feedback helps improve all SW, even if its just thanks or yikes):
www.eit.se/hb