Power: Arduino UNO board can be powered by external power supply using USB connection (Figure 9.2). It works on 5 V DC power supply, so board can be either connected with laptop through USB cable, or adapter can be used which converts AC into DC power supply. Board can also operate on 6–20 V power supply. Some of the power supply pins used on board are explained below:
- Vin: If board is pow
ered through external power source, this pin can be used. Supply can be given through this pin or can be accessed also when power is given by USB port. - 5 V: Power supply on this pin is regulated by 5 V DC power supply that is obtained from onboard regulator. Input power to voltage regulator is supplied through DC power jack or USB connector.
- GND (Ground): This pin can be used to make GND connections.
- IOREF: The main use of this pin is to supply reference voltage. This pin mainly works with 3.3 V DC power supply.
Memory: In Arduino UNO, ATMega microcontroller has 32 Kbytes of on-chip flash memory that is used by bootloader to upload Arduino IDE sketch. Moreover, 2 Kbytes of SRAM is used for runtime data usage and it also has 1 Kbyte of EEPROM (electrically erasable programmable read-only memory) memory.
Input and output pins: Arduino has two types of pins on board: digital pins and analog pins. Pins from 0 to 13 are used as digital input and output pins to receive and send digital data and these pins can be configured as in I/O mode using pinmode() command. These pins can be marked as LOW and HIGH using digital functions like digitalWrite() and can be read using digitalRead() functions.
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