Embedded Linux & BeagleY-AI: Cross-Compilation, Hardware, Networking, and Boot

Host

The development computer used to write and compile programs.

Target

The embedded device that runs the compiled application.

Native Compilation

Compiling a program for the same platform on which the compiler runs.

Cross-Compilation

Compiling on one platform to produce a program for a different target platform.

Cross-Compiler

A compiler that generates executable code for a different target architecture.

aarch64-linux-gnu-gcc

GCC cross-compiler used to build programs for 64-bit ARM Linux.

ABI (Application Binary Interface)

Rules governing data layout, function calls, return values, and binary compatibility.

ARM

A family of processor architectures commonly used in embedded systems.

BeagleY-AI

The ARM-based embedded Linux board used in the course.

GPIO (General Purpose Input/Output)

Pins used to read or produce digital HIGH and LOW signals.

I2C (Inter-Integrated Circuit)

A communication protocol used to communicate with integrated circuits such as accelerometers.

ADC (Analog-to-Digital Converter)

Hardware that converts an analog voltage into a digital number.

PWM (Pulse Width Modulation)

A digital signal whose duty cycle controls its average output level.

Duty Cycle

The percentage of one PWM period for which the signal is HIGH.

Virtual Machine (VM)

Software that allows a guest operating system to run on a host computer.

SSH (Secure Shell)

A protocol for securely accessing a remote computer's terminal.

Serial Communication

Communication that transmits data sequentially, one bit at a time.

RS-232

A serial communication standard using positive and negative signal voltages.

TTL-Level Serial

A serial interface using logic-level voltages such as 0 V and 3.3 V.

Baud Rate

The number of signaling symbols transmitted per second.

115200 8N1

Serial configuration with 115200 baud, 8 data bits, no parity, and 1 stop bit.

screen

A terminal program used to access a serial connection.

Ethernet over USB

A USB connection that creates a network interface between host and target.

DHCP (Dynamic Host Configuration Protocol)

A protocol for automatically assigning IP configuration to devices.

IP Address

A network address identifying an interface on an IP network.

ip addr

Linux command that displays network interfaces and IP addresses.

ping

Command that tests network reachability using ICMP echo requests.

ssh debian@192.168.7.2

Example command to open an SSH session to the target.

NFS (Network File System)

A protocol allowing a computer to access directories shared over a network.

mount

Command used to attach a filesystem to the Linux directory hierarchy.

sudo

Executes a command with elevated privileges when authorized.

chmod

Changes file permissions.

chown

Changes file ownership.

grep

Searches text for matching patterns.

dmesg

Displays messages from the Linux kernel.

Shell Pipe (|)

Passes one command's standard output to another command's standard input.

Output Redirection (>)

Writes command output to a file, normally overwriting existing contents.

U-Boot

A bootloader that initializes hardware and loads the Linux kernel.

Linux Kernel

The core of Linux responsible for scheduling, memory management, processes, and I/O.

Root File System (RFS)

The filesystem containing Linux user programs, libraries, and system files.

Boot Sequence

The startup order U-Boot, Linux kernel, then root filesystem and userspace.

BOOT Partition

A microSD partition containing boot-related files and configuration.

rootfs Partition

A microSD partition containing the Linux root filesystem.

bb-imager

Utility used to prepare a BeagleY-AI microSD card and initial configuration.

sysconf.txt

A file used to configure initial target settings during boot.

Work Directory

Private development folder containing source code and project files.

Public Directory

Folder containing files shared with the embedded target.

NFS Mount Point

The local directory where a network-shared filesystem becomes accessible.

Makefile

A file defining rules and commands for building software.

GNU Make

A build utility that executes rules defined in a Makefile.

Make Target

A named build goal or action defined in a Makefile.

make

Runs the default build target.

make clean

Runs the clean target, typically removing generated files.

make all

Runs the target named all, often used to build the full project.

CC_C

A Makefile variable commonly used to store the C compiler command in this course.

CFLAGS

A Makefile variable commonly used to store C compiler options.

-Wall

Enables a collection of compiler warnings.

-g

Includes debug symbols in a compiled executable.

-Werror

Treats compiler warnings as errors.

-std=c11

Requests the C11 language standard.

-D_POSIX_C_SOURCE=200809L

Requests interfaces associated with the specified POSIX feature-test version.

CMake

A cross-platform meta build system used to configure and generate build files.

Meta Build System

A tool that generates build-system files from higher-level project configuration.

CMakeLists.txt

The file describing a CMake project's build configuration.

cmake_minimum_required()

Specifies the minimum CMake version required by a project.

project()

Defines project information such as name, version, and language.

add_executable()

Defines an executable target and its source files in CMake.

add_compile_options()

Adds compiler options for applicable targets.

CMAKE_C_STANDARD

CMake setting specifying the requested C language standard.

cmake -S . -B build

Configures the current source directory and generates build files in build.

cmake --build build

Compiles and links a configured CMake project.

CMake Kit

Toolchain configuration used to choose compilers and build settings in VS Code.

HAL (Hardware Abstraction Layer)

A software layer that hides hardware-specific details behind an interface.

nano

A terminal-based text editor.

vi

A modal text editor with command and insert modes.

vi Insert Mode

The mode used to type and edit text.

vi Command Mode

The mode used for navigation, saving, deleting, and other editor commands.

vi :wq

Saves the file and quits vi.

vi :q!

Quits vi without saving changes.

vi dd

Deletes the current line.

Append Redirection (>>)

Adds command output to the end of a file.

cat

Displays file contents.

less

Displays text one screen at a time.

tail -20

Displays the last 20 lines of input.

K&R C

The early C language description associated with Kernighan and Ritchie.

ANSI C / C90

The first widely standardized version of C.

C99

C standard introducing features such as // comments and declarations in for loops.

C11

C standard adding features including threading-related support.

IDE (Integrated Development Environment)

Software combining code editing, building, and debugging tools.

Modular Design

Dividing a program into separate components with clear responsibilities.

Header File (.h)

A file commonly containing public declarations, types, and constants.

Source File (.c)

A file containing C function implementations and private module details.

Function Prototype

A declaration specifying a function's return type and parameters.

Header Guard

Preprocessor directives preventing repeated processing of a header.

Encapsulation

Hiding internal data and implementation behind a controlled public interface.

Variable Scope

The region of source code where a variable's name is visible.

Local Variable

A variable declared within a block and accessible only within its scope.

Global Variable

A variable declared at file scope, outside functions.

Static Local Variable

A block-scope variable that retains its value across function calls.

Static Global Variable

A file-scope variable whose name has internal linkage.