... microcontroller. The microcontroller has 26 I / O ports, this project requires the use of 17 I / O ports (of ... output ports), to prevent electromagnetic interference, seven unused I / O ports through 10K resistor connected to 3. ... 3V power supply: as an input pin I / o ports, can be formulated as "input only ... "; as an output pin I / o port can be formulated as a "push ...