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Hands-on: remix it into your own Tilt Monitor

Module 1 — Getting started: run the real thing, then take it apart · Slides: slides.md · Module overview · Course page

Remix the three sensor apps into your own Tilt Monitor by filling the four blanks at the heart of the skeleton, then swap the sensor, change the display, and deliberately break and fix it, until you can place every line in its beat.

Objectives

Section titled “Objectives”

By the end of this lesson, you will:

  1. Fill the four blanks in practice/s02_anatomy_sensor.py (motion, dsp.tilt, seg.text, raise KeyboardInterrupt) until tilting the board moves both gauges, the dominant angle shows on the Seg7, the panel turns TILTED at 20 degrees, and the back button ends the program.
  2. Diagnose a still needle, an angle stuck at zero, a big number that never changes, and a back button that does nothing — each to the blank that’s still empty.
  3. Make at least one remix that differs from the originals (switching to sensors.radar(), or changing the display), and point out which line belongs to which beat, and what each sensors.* and dsp.tilt call does.

Before you start

Section titled “Before you start”

You’ve been through lesson 1.4, and remember the three-app comparison table: what “read, compute, draw” means for each app. Open the practice file in BENTO IDE, and keep your learning log ready to note what you changed in your remix, and why.

Concepts

Section titled “Concepts”

Our task is a Tilt Monitor: take the “read” slot from 01 (bmi270.motion()), the “compute” slot from 02 (dsp.tilt), and the “only redraw on change” trick from 04, and blend them into a new app. A pair of arc gauges shows pitch and roll, a Seg7 shows the largest tilt angle, and a LEVEL/TILTED label changes colour past TILT_LIMIT = 20 degrees. The constants DEAD and TILT_LIMIT at the top of the file are the easiest knobs to remix.

The practice file already gives you beats 1–2 (import and creating widgets) in full — the four blanks sit exactly in beats 3–4: read the IMU, convert it into an angle, put the dominant angle on the Seg7, and raise KeyboardInterrupt when the back button is pressed. Notice the event-driven drawing nested two levels deep: the outer check is whether the angle changed, the inner check is whether the tilted/flat status changed — both exist to avoid touching the screen more than necessary.

Remixing is the heart of PRIMM’s Modify step: swap the sensor (read sensors.radar() and show presence or energy instead of an angle — the skeleton doesn’t need touching), change the display (Seg7 to a Bar, change TILT_LIMIT to 10), and break and fix (move ui.Arc(...) into the loop, watch the screen flicker, then move it back). A remix that runs but that its own author can’t explain doesn’t count yet — the goal is “being able to read it,” not just “copying it until it runs.”

Worked example

Section titled “Worked example”

s02_anatomy_sensor_full.py is a polished version that adds an |a| bar, remembers the peak angle ever seen, and a Reset button. Open it once your own practice file is working, to compare how it builds on the same skeleton.

File What this file teaches
examples/s02_anatomy_sensor_full.py A Tilt Monitor remix (full version)

Practice

Section titled “Practice”

The file has 4 blanks (lines 62, 67, 76 and 96), each marked with a # TODO: comment. 1) ax, ay, az, gx, gy, gz = sensors.bmi270.motion() 2) roll, pitch = dsp.tilt(ax, ay, az) 3) seg.text("%d" % ang) 4) raise KeyboardInterrupt. Tilt the board slowly and check whether the needle, the number and the label all respond.

Practice file Topic
practice/s02_anatomy_sensor.py Taking apart a sensor app’s structure, then remixing it yourself (the fill-in-the-code version)

Solution

Section titled “Solution”

Open the solution after trying on your own at least once, and read how to use the solutions first.

Solution Pairs with
solution/s02_anatomy_sensor.py practice/s02_anatomy_sensor.py

Check your understanding

Section titled “Check your understanding”

The same questions are in quiz.yaml for automated checking.

  1. What’s the Tilt Monitor’s second blank? (single choice · objective 1)

    • a) ax, ay, az, gx, gy, gz = sensors.bmi270.motion()
    • b) roll, pitch = dsp.tilt(ax, ay, az)
    • c) seg.text(“%d” % ang)
    • d) raise KeyboardInterrupt
    Solution

    b — blank 1 reads, blank 2 computes the angle with dsp.tilt, blank 3 draws the dominant angle, and blank 4 exits the loop when the back button is pressed, matching the read-compute-draw-listen skeleton.

  2. You run it and the needle never moves, and the angle stays at 0 no matter how you tilt the board. What’s the most likely cause? (single choice · objective 2)

    • a) Blank 1 hasn’t been filled in yet, so ax, ay, az are stuck at 0, so dsp.tilt always gets an angle of 0
    • b) Forgot to fill in raise KeyboardInterrupt
    • c) TILT_LIMIT is set too high
    • d) The screen is broken
    Solution

    a — the placeholder line ax = ay = az = ... = 0 lets the program run, but with zero values — a clue while debugging that the sensor-reading blank is still empty.

  3. Pressing “< back” doesn’t end the program; it keeps looping forever. Which blank is still empty? (single choice · objective 2)

    • a) Blank 1
    • b) Blank 2
    • c) Blank 3
    • d) Blank 4, raise KeyboardInterrupt inside ui.poll
    Solution

    d — without raising inside the ui.poll loop, the program sees the button’s event but does nothing about it, so it just keeps looping.

  4. You want the same app to show whether someone is in front of the board instead of the tilt angle. What’s the main thing to change? (single choice · objective 3)

    • a) Rewrite the whole file’s skeleton
    • b) Change the read slot to sensors.radar() and the compute slot to bool(r[“presence”]); leave poll and the back button as they are
    • c) Only change TILT_LIMIT
    • d) Remove ui.poll entirely
    Solution

    b — the three-app comparison table is the remix map: swapping the read and compute slots gives you a whole new app; the rest of the skeleton doesn’t need touching.

Lab

Section titled “Lab”

The MVP for lessons 1.4–1.5: a remix that genuinely differs from the originals, with every part explained by which beat it belongs to.

  • All four blanks in the practice file are filled in, running on the emulator or the board with the needle, the dominant angle, and the status label all working.
  • Make at least one remix that differs from 01/02/04, and note in your learning log what you changed and why.
  • Try break-and-fix: move a widget’s creation into the loop, observe the symptom, then move it back.
  • Be able to point out which line in your file belongs to import, create-once, loop, or poll.

Going further

Section titled “Going further”

In the next pair of lessons (1.6–1.7), we’ll take the edge AI app apart the same way, then remix it to switch models and trigger an action on a matching class.

Next lesson: lesson 1.6 — Taking apart the edge AI app: the model registry, verdicts and actions

Reflect

Section titled “Reflect”
  • Which slots of the four-beat skeleton did your remix actually change? What does the part you never touched tell you about this program’s design?
  • When you moved the widget into the loop, what symptom did you see, and what do you think would happen if you left it that way for a long time?

Review questions

Answer on your own first, then open the answer.

  1. Which statement fills blank 2 of the Tilt Monitor? (Objective 1)

    1. ax, ay, az, gx, gy, gz = sensors.bmi270.motion()
    2. roll, pitch = dsp.tilt(ax, ay, az)
    3. seg.text("%d" % ang)
    4. raise KeyboardInterrupt
    Show answer

    Answer: B. roll, pitch = dsp.tilt(ax, ay, az)

    ช่อง 1 อ่าน ช่อง 2 คำนวณมุมด้วย dsp.tilt ช่อง 3 วาดมุมเด่น และช่อง 4 ออกจากลูปเมื่อกดปุ่ม back ตรงกับโครงอ่าน คำนวณ วาด ฟังปุ่ม

  2. After running, the needles never move and the angle stays 0 even when tilting. What is the most likely cause? (Objective 2)

    1. ยังไม่ได้เติมช่อง 1 ax ay az จึงค้างเป็น 0 ทำให้ dsp.tilt ได้มุม 0 เสมอ
    2. ลืมเติม raise KeyboardInterrupt
    3. TILT_LIMIT ตั้งไว้สูงเกินไป
    4. จอเสีย
    Show answer

    Answer: A. ยังไม่ได้เติมช่อง 1 ax ay az จึงค้างเป็น 0 ทำให้ dsp.tilt ได้มุม 0 เสมอ

    บรรทัดสำรอง ax = ay = az = ... = 0 ทำให้โปรแกรมรันได้แต่ค่าเป็นศูนย์ เป็นเบาะแสตอน debug ว่าช่องอ่านเซนเซอร์ยังว่าง

  3. Pressing the back button does not end the program. Which blank is still empty? (Objective 2)

    1. ช่อง 1
    2. ช่อง 2
    3. ช่อง 3
    4. ช่อง 4 raise KeyboardInterrupt ใน ui.poll
    Show answer

    Answer: D. ช่อง 4 raise KeyboardInterrupt ใน ui.poll

    ถ้าไม่ raise ในลูป ui.poll โปรแกรมจะเห็นอีเวนต์ของปุ่มแต่ไม่ทำอะไร จึงวนต่อไปเรื่อย ๆ

  4. You want the same app to show whether someone is in front of the board instead of the tilt. What do you mainly change? (Objective 3)

    1. เขียนโครงใหม่ทั้งไฟล์
    2. เปลี่ยนช่องอ่านเป็น sensors.radar() และช่องคำนวณเป็น bool(r["presence"]) ส่วน poll และปุ่ม back คงเดิม
    3. เปลี่ยนแค่ TILT_LIMIT
    4. ลบ ui.poll ทิ้ง
    Show answer

    Answer: B. เปลี่ยนช่องอ่านเป็น sensors.radar() และช่องคำนวณเป็น bool(r["presence"]) ส่วน poll และปุ่ม back คงเดิม

    ตารางเทียบสามแอปคือแผนที่ remix สลับช่องอ่านกับคำนวณก็ได้แอปใหม่ โครงที่เหลือไม่ต้องแตะ

Cite this lesson

If you teach from this lesson or reuse it in slides or documents, credit it with the text below. If you changed it, add (adapted) after the title.

"Hands-on: remix it into your own Tilt Monitor" from TESA Open Knowledge by the Thai Embedded Systems Association (TESA), https://github.com/tesaiot/tesa-qualification-program, licensed under CC BY-NC 4.0

Thai attribution: "ลงมือทำ: remix เป็น Tilt Monitor ของเรา" จาก TESA Open Knowledge โดยสมาคมสมองกลฝังตัวไทย (Thai Embedded Systems Association: TESA) https://github.com/tesaiot/tesa-qualification-program สัญญาอนุญาต CC BY-NC 4.0

Lesson link: https://tesaiot.github.io/tesa-qualification-program/en/courses/edge-ai-developer/m01-onboarding/l05-sensor-remix-lab/

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TESA Open Knowledge · © 2026 สมาคมสมองกลฝังตัวไทย (TESA) · CC BY-NC 4.0

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