The Arduino subfolder of the Hardware section contains support for 2 architectures; AVR and SAM. The AVR Microcontrollers are included in the most common Arduino boards like the Uno, Nano, Mega, etc. However, some Arduino Boards like the Arduino Due don’t use AVR but use the SAM 32-bit ARM processors.

The different types of Arduino Boards which are also commonly referred to as “Variants” are present in the boards.txt file. This is a particularly important file because it contains the different configuration information for different Arduino Boards like which compiler toolchain to execute on a particular variant.

The SD.h library for communication between SD Card Modules and Arduinos uses SPI (Serial Peripheral Interface) for establishing communications. The SPI is a synchronous Serial Communication Protocol that is used for short-distance communications between microcontrollers and devices like SD Card Readers, shift resistors, etc.

Setup() is called once in the program when a sketch starts after power-up. It is used to initialize variables, input and output pin modes, and other libraries needed in the sketch. Loop() is used after setup() been called, function loop() is executed repeatedly in the main program. It controls the board until the board is powered off or is reset.

All C code is compiled to a .o file. This file format is called the Object File Format. The compiler creates these object files during compilation, for each source code and then links each of these together for making the executable file for that language.

Pico power technology employs advanced features like multiple clock domains, DMA and event systems to minimize power consumption

There are 3 configuration files that allow a person to tweak the configurations. These include the following files; platform.txt, boards.txt, and programmers.txt. These files are all really important in defining the architecture for different processors.

The SD.h Library in Arduino allows for communications between the Arduino Board and an SD Card Module for storage and retrieval of data. It is dependent on the sdfatlib library which works on FAT16 and FAT32 filesystems.

During the compilation process, the Arduino compiler before compilation searches for previously generated “.o” files in the directory, to make the compilation process faster in some cases. This reduces the redundancy of compiling the same parts of the code repeatedly.

The Atmega2560 has a total of 6 timers, of which 2 are 8-bit timers and 4 are 16-bit timers. The number of bits here represents the resolution of the timers, I.e. the number of bits each timer can store.

The LCD Library in Arduino allows for controlling LCD Displays with the Arduino. This is based on the Hitachi HD44780 Chipset which is a dot-matrix LCD (Liquid Crystal Display) Driver. It can be configured and used with 4-bit and 8-bit microcontrollers.

The optiboot bootloader will take 512 bytes, leaving 32256 bytes for the application code. Due to its small size, larger up-loadable sketch size is achieved.

The AVR-GCC/G++ software is a compiler that can take C/C++ code as input and translate or compile it into Binary Code that follows the instruction set for the AVR Microcontrollers. They’re used in the Arduino software since most Arduino Boards use the AVR Microcontroller family.

Sketches are saved on the development computer as text files with the file extension .ino. Arduino software (IDE) pre-1.0 saved sketches with the extension file .pde.

The Arduino.h file is not something that we encounter during the process of writing the code for the Arduino board because the preprocessor takes care of it before compilation. However, it is a very important file without which we cannot access the Arduino’s features like GPIO IO, Analog IO, etc.

The Arduino boards can connect with add-on modules termed shields. Multiple and possibly stacked shields may be individually addressable via an I2C serial bus

The Wire library is used to communicate data with the I2C (Inter IC) or TWI (Two Wire Interface) Bus which are almost identical to each other and are used for communicating data to different microcontrollers.

The assembly instructions for the microcontroller is stored in a hex file. This file contains the assembly instructions in hex format for the microcontroller to understand and execute. It is the binary executable file that allows us to execute the high-level C code on any microcontroller.

A verbose is a feature that reports all information in a process, function or code. The Arduino Verbose Output helps in displaying the output for each execution step in the Arduino Compilation Process.

There are 4 Arduino boards and 4 Arduino shields that fit on top of Arduino compatible boards to provide additional capability like connecting to the internet, motor controller, LCD screen controlling, etc.,.

Level shifters are used in multi-design, different blocks work on different voltage levels. So when a signal passes from one voltage domain to another voltage this is needed particularly when a signal passes from low level to high level.

The GSM library on the Arduino helps the user to perform call, SMS, or even Internet Communications via the GSM Module. This library works in conjunction with the GSM Shield which uses a modem and AT commands to connect the Arduino to the GSM network.

A program for Arduino can be written in any programming language for a compiler that produces binary machine code for the target processor.