These are the bare minimum requirements to bring the chip to life and program it using the Arduino IDE. The 0.1uf capacitors are not optional - you must use these or the parts will behave erratically, and may not work at all; these should be placed as close to the chip as possible.
- Vcc pin(s) connected to supply voltage (1.8~5v depending on part, clock speed, and fuse settings)
- Gnd pin(s) connected to Ground
- 0.1uf ceramic capacitor connected between Vcc and Gnd pins, as close to the part as practical.
- If part has multiple Vcc pins, there should be 0.1uf cap from each one to ground, right next to the chip.
- If part has an AVcc pin, that should be connected to Vcc.
- If part has an AGnd pin, that should be connected to Gnd.
- If part has an AVcc pin and an AGnd pin, 0.1uf ceramic capacitor between AVcc and AGnd, right next to the chip.
- If part has an AVcc pin but no AGnd pin, 0.1uf cerapic capacitor between AVcc and Gnd, right next to the chip.
If the power supply is unstable, or the wires from the supply are long, it is highly recommended to put a larger capacitor between power and ground on the board - the appropriate size and type will depend on the loading, voltage, stability of the power supply, and available space; typical values might range from 10 uf to 1000uf. Aluminum electrolytic caps are commonly used for this purpose.
- 10k resistor between Reset pin and Vcc
- 0.1uf capacitor between Reset pin and pin header that you can connect to the DTR pin of your serial adapter
- Diode (any) between Reset and Vcc, band towards Vcc. Necessity of this part is debated.
It is recommended that you install a 1x6 pin FTDI header for ease of connection to the serial adapter. The pinout of this is:
- Gnd
- Not used
- Vcc
- Rx (this will go to Tx of serial adapter)
- Tx (this will go to Rx of serial adapter)
- DTR
See the Programming Guide for more information.