The DFRduino Duemilanove 168 (SKU:DFR0002) or DFRduino Duemilanove 328 (SKU:DFR0001)

on the DFRduino Nano comes preburned with a bootloader that allows you to upload new code to it

without the use of an external hardware programmer. It communicates using the original STK500

protocol (reference, C header files).

You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit

Serial Programming) header; see these instructions for details.

Automatic (Software) Reset

Rather then requiring a physical press of the reset button before an upload, the DFRduino Nano is

designed in a way that allows it to be reset by software running on a connected computer. One of

the hardware flow control lines (DTR) of the FT232RL is connected to the reset line of the

ATmega168 or ATmega328 via a 100 nanofarad capacitor. When this line is asserted (taken low),

the reset line drops long enough to reset the chip. The DFRduino software uses this capability to

allow you to upload code by simply pressing the upload button in the DFRduino environment. This

means that the bootloader can have a shorter timeout, as the lowering of DTR can be well-

coordinated with the start of the upload.

This setup has other implications. When the Nano is connected to either a computer running Mac

OS X or Linux, it resets each time a connection is made to it from software (via USB). For the

following half-second or so, the bootloader is running on the Nano. While it is programmed to ignore

malformed data (i.e. anything besides an upload of new code), it will intercept the first few bytes of

data sent to the board after a connection is opened. If a sketch running on the board receives one-

time configuration or other data when it first starts, make sure that the

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