Electronics Introduction

 An FPGA XDC is a Xilinx Design Constraints file (extension .xdc ) used in Vivado to tell the tools how your design must be connected and timed . Think of it as the “rules + wiring map” for implementation. What an XDC file contains 1) Pin assignments (physical I/O mapping) Maps your top-level ports to FPGA package pins and sets I/O standards. Example: set_property PACKAGE_PIN W5 [get_ports {clk}] set_property IOSTANDARD LVCMOS33 [get_ports {clk}] 2) Timing constraints (so timing analysis is correct) Defines clocks and timing relationships. Example: create_clock -period 10.000 [get_ports clk] ;# 100 MHz You can also constrain: input/output delays ( set_input_delay , set_output_delay ) clock uncertainty, generated clocks, false paths, multicycle paths, etc. 3) I/O electrical constraints Sets things like: IOSTANDARD (LVCMOS33, LVDS, SSTL, etc.) drive strength ( DRIVE ) slew rate ( SLEW FAST/SLOW ) pullups/pulldowns ( PULLUP , PULLDOWN ) 4) Ot...

 On a Raspberry Pi 4B (Raspberry Pi OS), you “add programs” mainly in these ways: 1) Easiest (GUI): Add/Remove Software If you’re using the desktop: Menu → Preferences → Add/Remove Software Search the app → install This uses the same package system as the terminal (APT).  2) Recommended (Terminal): APT packages APT is the standard/recommended way to install/update/remove software on Raspberry Pi OS.  sudo apt update sudo apt install <package-name> Examples: sudo apt install git sudo apt install python3 sudo apt install vlc To update everything: sudo apt update sudo apt full-upgrade To remove: sudo apt remove <package-name> sudo apt autoremove 3) Install a downloaded .deb package If you downloaded a Debian package (must match your architecture: armhf/arm64 , not x86_64):  cd ~/Downloads sudo apt install ./some-package.deb (Using apt install ./file.deb is nice because it pulls dependencies automatically.) 4) Python...

 Interrupts are how a microcontroller stops what it’s doing (briefly) to handle an important event right now , then returns to exactly where it left off. Here’s how it works “under the hood”, step by step. The core idea Your main code runs in a loop (or an RTOS task). Hardware events happen asynchronously: a timer hits zero, a UART byte arrives, a GPIO edge occurs, ADC completes, etc. Instead of polling (“are we there yet?”), the MCU uses an interrupt : a hardware signal that asks the CPU to run a specific function called an ISR (Interrupt Service Routine). What happens when an interrupt occurs (exact sequence) 1) An event sets an interrupt flag Example: a timer overflows → the timer peripheral sets a status bit like TIMERx_IF = 1 . 2) The interrupt controller decides if it should fire An interrupt triggers the CPU only if: The peripheral’s interrupt is enabled (local enable bit), The interrupt is unmasked/enabled in the interrupt controller (e.g., N...

  analogWrite() makes an Arduino pin output a PWM (pulse-width modulated) signal that behaves like an “analog” level to things like LEDs and DC motors. What it actually does Outputs a square wave that switches HIGH/LOW quickly. You set a value (usually 0–255 ) that controls the duty cycle (how long it stays HIGH each cycle). analogWrite(pin, 0) → always OFF (0% duty) analogWrite(pin, 255) → always ON (100% duty) analogWrite(pin, 128) → ~50% duty What it’s used for LED dimming (brightness follows duty cycle) Motor speed control (with a driver/ MOSFET ) Generating a basic PWM control signal (e.g., for some devices) Important notes It only works on PWM-capable pins (marked with ~ on many boards). It does not output a true analog voltage by itself. If you want a real DC voltage, you need: a low-pass RC filter , or a DAC pin (some boards like Due/Zero have DAC ), or an external DAC. PWM frequency depends on the board ...

 On STM32 , “ALT pins” usually means alternate functions (AF): using a GPIO pin for USART/SPI/I²C/TIM PWM/ADC, etc. You pick the pin’s AF mapping in CubeMX (or write the GPIO registers yourself). Here’s the practical way. The CubeMX way (recommended) Open STM32CubeMX (or CubeIDE → .ioc ). Go to Pinout & Configuration . Enable the peripheral you want (e.g., USART1 , SPI2 , TIM3 PWM ). CubeMX will assign default pins. To use “alt pins”: Click the pin on the package view (e.g., PA9) Choose the function you want (e.g., USART1_TX ) Or open the peripheral settings → GPIO Settings and select alternate pins there. In GPIO Configuration ensure: Mode = Alternate Function Push-Pull (most digital AF signals) Pull-up/down as needed Speed set appropriately (higher for fast edges like SPI) Generate code. CubeMX will create: MX_GPIO_Init() HAL_UART_MspInit() / HAL_SPI_MspInit() etc. that set the AF. Typical HAL GPIO init snippet ...

 In Verilog (and SystemVerilog), functions and tasks are both ways to package reusable logic—but they’re meant for different kinds of work. Getting this right matters in FPGA RTL because it affects synthesizability, timing, and code clarity . Functions vs Tasks (the core differences) Function Use a function when you want a pure calculation that: returns one value takes inputs does not consume time (no #delay , no @event , no wait ) is typically used inside expressions (RHS of assignments, conditions, parameters) Think: “combinational math / bit manipulations / encoding / decoding”. Task Use a task when you want a procedure that: may return multiple values via output/inout arguments is called from procedural code ( always , initial , etc.) in testbenches , can include time/event controls in synthesizable RTL , must still be zero-time (no delays/events) Think: “do these steps” (especially in testbenches), or “group repeated procedural c...