Editing AVR microcontrollers (section)

=== Butterfly demonstration board ===
[[File:ATmega169-MLF.jpg|thumb|Atmel ATmega169 in 64-pad [[MicroLeadFrame|MLF]] package on the back of an Atmel AVR Butterfly board]]
{{Main|AVR Butterfly}}
The very popular AVR Butterfly demonstration board is a self-contained, battery-powered computer running the Atmel AVR ATmega169V microcontroller. It was built to show off the AVR family, especially a then new built-in LCD interface. The board includes the LCD screen, joystick, speaker, serial port, real time clock (RTC), flash memory chip, and both temperature and voltage sensors. Earlier versions of the AVR Butterfly also contained a CdS [[photoresistor]]; it is not present on Butterfly boards produced after June 2006 to allow [[RoHS]] compliance.<ref>[http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3146 AVR Butterfly]</ref> The small board has a shirt pin on its back so it can be worn as a name badge.

The AVR Butterfly comes preloaded with software to demonstrate the capabilities of the microcontroller. Factory firmware can scroll your name, display the sensor readings, and show the time. The AVR Butterfly also has a piezoelectric transducer that can be used to reproduce sounds and music.

The AVR Butterfly demonstrates LCD driving by running a 14-segment, six alpha-numeric character display. However, the LCD interface consumes many of the I/O pins.

The Butterfly's ATmega169 CPU is capable of speeds up to 8&nbsp;MHz, but it is factory set by software to 2&nbsp;MHz to preserve the button battery life. A pre-installed bootloader program allows the board to be re-programmed via a standard RS-232 serial plug with new programs that users can write with the free Atmel IDE tools.