Tiny Arduino have only eight pins as shown in figure above, Pin4 is ground (Gnd), Pin8 is 5V (Vcc), Pin1 is Reset, Pin2 and Pin3 originally used to connecting the Crystal. In order to utilize all the IO, the internal oscillator (RC Oscillator) is used to replace the external clock which require a crystal. Therefore the Tiny Arduino is now come with five IO. Below shows the Arduino IO functions.
1. There are five IO, each IO can be Input or Output
2. Among the five IO, two of the IO can perform as PWM
3. Among the five IO, three of the IO can perform as Analog Input
I2C may require to extend the features of Tiny Arduino.