I have created a microcontroller circuit, based on the most used circuits I could find on the Internet -- which use an external crystal. As I know, Atmega16 has an internal oscillator which operates at 1 MHz by default. So, the microcontroller can be used without an external crystal. But now I am confused -- do I need an external crystal for my microcontroller circuit? I am just using ADC, USART, and LM35. I don't know if the internal oscillator is enough, good, or etc to be used.
So, when do we need an external crystal for our microcontroller?