I have tried to use pull up and pull down resistor: the result is the same. Only it works fine when I connect RX pin from ATMEGA328P to RX pin from Arduino Uno.
EDIT: I have solved adding delay on setup part.
I have tried to use pull up and pull down resistor: the result is the same. Only it works fine when I connect RX pin from ATMEGA328P to RX pin from Arduino Uno.
EDIT: I have solved adding delay on setup part.