OK, I will use external crystal.
dc42:
You need to connect Vcc to Vcc1, which is implied in your diagram but not very clear
You should connect Avcc1 to Avcc.
Consider adding a L-C decoupling network between Vcc and Avcc, as used on the Leonardo (see http://arduino.cc/en/uploads/Main/arduino-leonardo-schematic_3b.pdf) and recommended by the datasheet, unless you will not be using the ADC
Why I must connect Vcc to Vcc1 and Avcc to Avcc1?
On ATmega32u4 package (image below) I see a lot of +Voltage and GND.
Is it importatnt to connect it together?
- Vcc - pins 34 and 14 each on other side of package
- GND - pins 15, 23, 43
- AVCC - pins 24 and 44
these pins have the same name. Is it possible to connect only one of this? For example 14 to +5V and 43 to GND?
AVCC is for ADC? I do not want to use ADC converter. Can I ignore AREF and AVCC?
What about UVcc (pin 2) and UGnd (pin 5) and VBUS? Can/must I connect UVcc and VBUS to VCC? When I use +5V from USB, is it possible to conect +5V to ATmega only on one of these pins?
L-C between Vcc and Avcc is only for ADC converter? Can I ignore this?
