Abbrev.	Function	Description
MCU	Micro-processor Unit
GND	Ground
MOSI	Master Out Slave In	The data is transmitted from Master to Slave.
MISO	Master In Slave Out	The data is transmitted from Slave to Master.
ADJ	Adjustable Voltage Regulators
VCC	Voltage Common Collector
PWM	Pulse Width Modulation
I2C	Inter-Integrated Circuits
SDA	Serial Data	Bidirectional data line that is used by I2C
SCL	Serial Clock	To indicate that data is ready on bidirectional data line that is used by I2C.
DQ	Data Input/Output
TTL	Transistor-Transistor Logic
TX	Transmit	To transmit TTL serial data.
RX	Receive	To receive TTL serial data.
NC	No Connect
AREF	Analog Read Reference
FM	Female-Male
EN	Enable
DIO	Digital Input Output