Embedded Timing: Sample Without Blocking

Electronics and Embedded Systems · CHAPTER 4 / 5

Level: introductory undergraduate · Study session: 15–20 minutes including practice.

Learning outcome: Design a periodic task using elapsed time.

Before you begin: Complete earlier chapters in this discipline; revise algebra and units as needed.

1. Understand the idea

A blocking delay stops other work in a simple foreground loop. An elapsed-time check allows the loop to handle inputs between samples. Sampling needs a known interval, bounded execution time and adequate anti-alias filtering. Use the timer arithmetic recommended for your platform, including counter rollover handling.

2. Write the model

fs = 1/Ts; ideal Nyquist boundary = fs/2

Define the symbols from the worked case before substituting values. Keep units consistent, record the assumptions and round only after the calculation.

3. Follow a worked example

A 10 ms sample interval gives fs=100 Hz. An ideal 40 Hz component is below the 50 Hz Nyquist boundary, but practical filter transition bands require margin. A 70 Hz input can alias to 30 Hz when sampled at 100 Hz.

4. Explore the model

Figure: calculated teaching cases; straight segments connect sampled points, not experimental observations. Read exact values below.

Illustrative scenario sweep — synthetic educational data
Interval (ms)	Sampling rate (Hz)	Nyquist boundary (Hz)
5	200	100
10	100	50
20	50	25

Vary the interval and calculate the corresponding boundary. Explain why slower sampling can misrepresent a fast input.

5. Reproduce it yourself

Copy the input cases into Excel or a notebook and name each quantity and unit.
Recalculate each result from the stated equation or rule. For qualitative cases, explain the state or partition decision instead.
Change one input, predict the direction of change, then calculate again.
Write one sentence explaining where the model stops being valid.

6. Check your understanding

What rate follows from a 2 ms interval?

Reveal the answer and check your work

500 Hz.

Compare your result, units and reasoning. If they differ, return to the equation and test the worked case first.

7. Common mistake

Nyquist is not a promise of accurate measurement without filtering and timing control.

Further study and academic note

Explore the discipline reference and further learning resources. This is an original IIMEEE introductory teaching note with synthetic examples; it is not a peer-reviewed research result or a professional design specification. Figures were constructed from the listed teaching cases. Resource links support further study and do not imply endorsement.