luokai0 Embedded Systems Expert
Before Starting
- Bare-metal or RTOS-based?
- Which microcontroller family? (ARM, AVR, ESP32, STM32)
- Real-time constraints or resource constraints primary concern?
Core Expertise Areas
Microcontroller Fundamentals
Architecture: CPU core, flash, RAM, peripherals integrated on one chip. ARM Cortex-M: dominant family, M0 to M7, increasing performance and features. Memory map: code, SRAM, peripherals mapped to address space. Interrupts: NVIC handles priorities, ISR must be short and non-blocking. Startup code: initialize stack, copy data to RAM, zero BSS, call main.
Peripheral Interfaces
GPIO: general purpose IO, configure as input or output, pull-up or pull-down. UART: serial communication, baud rate, start and stop bits, parity. SPI: synchronous serial, four wires, master-slave, high speed. I2C: two-wire serial, multi-device on same bus, 7-bit addressing. PWM: pulse width modulation, motor control, LED dimming, DAC approximation.
RTOS
Task: independent thread of execution, priority, stack size. Scheduler: preemptive priority-based, context switch at tick or preemption. Semaphore and mutex: synchronization between tasks, prevent priority inversion. Queue: inter-task communication, FIFO data passing. FreeRTOS: most popular open source RTOS, widely supported.
Low-Power Design
Sleep modes: stop, standby, hibernate trade wake time for power savings. Clock gating: disable peripheral clocks when not in use. Voltage scaling: reduce core voltage at lower frequencies. Wake sources: RTC, GPIO interrupt, watchdog timer to exit low power mode.
Best Practices
- Keep ISRs short, set flags and return, process in main loop or task
- Use watchdog timer to recover from firmware hangs
- Test memory usage to avoid stack overflow
- Use hardware debugger not just printf for embedded debugging
Common Pitfalls
| Pitfall | Fix |
|---|---|
| Stack overflow | Size stack carefully, use RTOS stack monitoring |
| Race condition on shared data | Use mutex or disable interrupts around critical section |
| Floating point in ISR | Avoid FPU in ISR or save and restore FPU state |
| Blocking in ISR | Set flag in ISR, process in task or main loop |
Related Skills
- electronics-expert
- circuit-analysis-expert
- linux-expert