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Embedded Systems

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Embedded systems are computers built into a larger product — engine controllers, washing machines, drones, medical pumps, industrial sensors. They run a focused job under hard constraints on power, cost, and time.

Overview

Embedded engineers live close to the metal: registers, interrupts, DMA, watchdogs, bootloaders. The reward is determinism — you can usually account for every cycle.

Microcontrollers

  • ARM Cortex-M — M0/M0+/M3/M4/M7/M33 (STM32, NXP Kinetis, Nordic nRF, Microchip SAM).
  • RISC-V — ESP32-C3/C6, GD32V, SiFive.
  • AVR — ATmega, ATtiny (Arduino).
  • PIC — Microchip PIC16/18/24/32.
  • Espressif — ESP32 / ESP8266 with Wi-Fi/BLE.
  • SoCs / SoMs — i.MX, Zynq, Jetson when you need Linux.

Peripherals & Buses

  • GPIO, pull-ups, open-drain.
  • UART — async serial; baud, parity, stop bits.
  • SPI — full-duplex master/slave; MISO/MOSI/SCK/CS.
  • I²C — 2-wire multi-drop; 7- or 10-bit addressing.
  • CAN / CAN FD — automotive & industrial multi-master.
  • USB — Full/High/Super speed; CDC, HID classes.
  • ADC / DAC, PWM, timers, RTC.

RTOS & Bare-Metal

  • Bare-metal — super-loop or event-driven; simplest, hardest to grow.
  • RTOS — FreeRTOS, Zephyr, ThreadX (Azure RTOS), RTEMS, ChibiOS, NuttX.
  • Preemptive scheduling; priority inversion via priority inheritance.
  • Synchronization — mutex, semaphore, queue, event flags.

Firmware Practices

  • Bootloader + application; A/B partitions for safe OTA.
  • Watchdog timers + brown-out detect.
  • Defensive I/O — saturate, debounce, range-check.
  • HAL / driver split; mock hardware for unit tests.
  • MISRA C / CERT C for safety-critical code.

Tools

  • IDEs: STM32CubeIDE, MPLAB X, PlatformIO, Keil μVision, IAR EWARM.
  • Debug: J-Link, ST-Link, Black Magic Probe, OpenOCD, GDB.
  • Analysis: Saleae logic analyzer, Bus Pirate, oscilloscope.
  • Toolchain: arm-none-eabi-gcc, LLVM.
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