How do I fix timing issues in my MCU program?

Fixing timing issues in an MCU (Microcontroller Unit) program involves identifying where time-related errors occur—such as delayed response, drift, jitter, or missed events—and applying appropriate software or hardware solutions. Here's how you can methodically address them:

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1. Identify the Nature of the Timing Issue

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🛠️ 2. Use Hardware Timers Instead of Software Delays

Bad (timing-sensitive code):

c

delay(100); // Blocks CPU

Better (non-blocking using millis() or timer interrupt):

c

if (millis() - previousTime >= 100) {
    previousTime = millis();
    // Perform action
}

Best (RTOS or hardware timer-based):

• Configure a hardware timer interrupt (e.g., every 1 ms) to handle precise periodic tasks.

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3. Calibrate or Configure System Clock Properly

• Ensure the system clock source (HSE, HSI, PLL, etc.) is set correctly.

• On STM32, check SystemClock_Config() or use CubeMX to configure accurately.

• Use external crystals or TCXOs for long-term timing stability.

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4. Avoid Blocking Code

Blocking functions (like delay(), while(!flag);) can:

• Delay other tasks

• Cause timing inconsistency

Instead:

• Use state machines

• Use interrupt-driven approaches

• Implement non-blocking delays using system tick or timers

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5. Prioritize and Optimize ISRs (Interrupt Service Routines)

Poor ISR handling can cause missed events:

• Keep ISRs short and fast

• Set correct interrupt priority levels

• Avoid heavy computations inside ISRs

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6. Use RTOS for Multitasking (if needed)

If you're running multiple tasks with different timing needs:

• Use an RTOS like FreeRTOS

• Assign each task to run at a specific rate

• Use software timers or task delays

Example:

c

vTaskDelay(pdMS_TO_TICKS(100)); // Delay a task for 100ms

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7. Add Logging or Oscilloscope Tracing

• Use GPIO toggling and measure timing with an oscilloscope.

• Use UART logs with timestamps to find execution delays.

• Use tools like STM32CubeMonitor, Logic Analyzers, or Segger SystemView.

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Summary: Common Fixes