Rico贾若童的博客

Linux - Filesystem

inode, soft/symbolic link, FIFO, File Lock

Inode On every Unix-style filesystem (ext4, XFS, APFS, etc.), each regular file, directory, FIFO, … is represented on disk by a tiny metadata record called an inode (“index node”). That’s like a f...

Posted by Rico's Nerd Cluster on January 10, 2018

Linux - Udev Rules, Systemd Services, inotify

Udev Rules Systemd Services, Inotify

Udev Unix Kernel is a monolithic kernel and provides API to access these hardware. Udev is a device manager of Linux Kernel, and serves as a successor of the Unix Kernel. It handles device nodes i...

Posted by Rico's Nerd Cluster on January 7, 2018

Linux - SSH and X Window System

X Window System, SSH, Static IP

What is X? X Window System (or X11, X) renders graphics on display hardware. It can interact with input devices such as a mouse, keyboard, etc., to create effects like dragging windows and click...

Posted by Rico's Nerd Cluster on January 5, 2018

Electronics - General Science Facts

Adiabatic Cooling, Centripedal & Centrifugal Forces

Adiabatic Cooling In an adiabatic process, the system does not gain or lose heat (Q=0Q=0), meaning that all changes in internal energy come from work done by or on the gas. For an ideal gas, the i...

Posted by Rico's Nerd Cluster on July 1, 2017

Literature - The Wealthy Barber Notes

Financial Literacy

Roy’s Story “We all felt bad about Roy having to put off his dream of becoming a lawyer, but deep down we knew that he was doing the right thing. You got to be there when your family needs you,...

Posted by Rico's Nerd Cluster on June 5, 2017

Electronics - General Electronics Notes

Encoders, Motors, Capacitors, IMU, Testing, Telecommunication

Electronics EEPROM EEPROM (Electrically Erasable Programmable Read-Only Memory) is a type of non-volatile memory used in microcontrollers to store small amounts of data that must be preserved whe...

Posted by Rico's Nerd Cluster on June 3, 2017

Electronics - Embedded Systems Notes

HAL

HAL vs SAL Hardware Abstraction Layer (HAL) is software that abstracts hardware-specific details from the application or higher-level software. It provides a unified API for accessing hardware fun...

Posted by Rico's Nerd Cluster on June 1, 2017

Electronics - Communication Protocols

Encoding / Decoding, Error Checking (CRC), Base64, EtherCAT

Error Checking CRC GF(2) Math GF(2) is pronounced as “Galois Field 2”. Often used in cryptography, it’s a binary field that contains only 0 and 1 for error correction. Some properties of GF(2):...

Posted by Rico's Nerd Cluster on June 1, 2017

Electronics - EMF and Eddy Current

Electromotive Force (EMF，电动势) In short, EMF is: 1 changing magnetic field -> induced voltage It’s characterized by the Faraday’s law: \[\begin{gather*} \begin{aligned} & \epsilon = -N \...

Posted by Rico's Nerd Cluster on June 1, 2017

Math - Differential Entropy

Differential Entropy Differential entropy is the entropy version for a continuous random variable. For a discrete variable: 1 2 3 4 H(x) = -sum(p(x) * log(p(x))) // continuous version h(X) = -∫ ...

Posted by Rico's Nerd Cluster on March 5, 2017

Rico's Nerd Cluster

Linux - Filesystem

inode, soft/symbolic link, FIFO, File Lock

Linux - Udev Rules, Systemd Services, inotify

Udev Rules Systemd Services, Inotify

Linux - SSH and X Window System

X Window System, SSH, Static IP

Electronics - General Science Facts

Adiabatic Cooling, Centripedal & Centrifugal Forces

Literature - The Wealthy Barber Notes

Financial Literacy

Electronics - General Electronics Notes

Encoders, Motors, Capacitors, IMU, Testing, Telecommunication

Electronics - Embedded Systems Notes

HAL

Electronics - Communication Protocols

Encoding / Decoding, Error Checking (CRC), Base64, EtherCAT

Electronics - EMF and Eddy Current

Math - Differential Entropy

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