{ "schema": "tinyskiff.lessonPacket.v0", "lessonCode": "TSK-DAY08-METEOR", "course": "TinySkiff ESP32-S3 Lab", "day": 8, "title": "Send a comet down the bar", "status": "published", "learnerProfile": "adult beginner; curious and capable; no electronics assumed", "estimatedTimeMinutes": 20, "mission": "Rebuild the Day 6 LED bar, upload the Arduino sketch, and watch a bright head with a fading tail glide along the bar and back — the first time each segment holds its own brightness instead of full on or full off.", "mainPath": "Arduino/C++", "optionalSidePath": "MicroPython", "sourceMetadata": { "officialPdf": "source/Freenove_Super_Starter_Kit_for_ESP32_S3-main/C/C_Tutorial.pdf", "chapter": "Chapter 3 LED Bar", "page": 56, "arduinoSketch": "source/Freenove_Super_Starter_Kit_for_ESP32_S3-main/C/Sketches/Sketch_04.2_FlowingLight2/Sketch_04.2_FlowingLight2.ino", "micropythonFile": "source/Freenove_Super_Starter_Kit_for_ESP32_S3-main/Python/Python_Codes/04.2_FlowingLight/FlowingLight.py", "imageAsset": "docs/course/assets/day-08/circuit-page-56.png", "imageAlt": "Official Freenove LED bar circuit: ten LED segments, each driven from its own GPIO pin through a 220 ohm resistor and returning through a shared common row to ground, shown as both a schematic and a breadboard photo.", "licenseNote": "Based on Freenove official material released under CC BY-NC-SA 3.0; preserve attribution and non-affiliation language.\n" }, "parts": [ { "name": "ESP32-S3 board", "imageAsset": "docs/course/assets/shared/item-esp32-s3-board.jpg", "explanation": "A development board is a friendly package around a tiny computer chip. The ESP32-S3 runs your uploaded sketch, controls pins, reads sensors, and can also use USB, Wi-Fi, and Bluetooth. In this lesson, it sends the ping signal and measures the echo time." }, { "name": "GPIO extension board", "imageAsset": "docs/course/assets/shared/item-gpio-extension-board.png", "explanation": "GPIO means general-purpose input/output. These pins are connection points your code can use. The extension board makes them easier to see, reach, and wire without cramming everything onto the ESP32-S3 itself." }, { "name": "LED bar graph", "imageAsset": "docs/course/assets/shared/item-led-bar.png", "explanation": "A LED bar packs ten separate LEDs into one strip, with a row of pins along each edge. Each LED is wired and driven on its own — exactly like the single LED from earlier days, just ten of them in a tidy line." }, { "name": "8 × 220 Ω resistors", "imageAsset": "docs/course/assets/shared/item-resistor.png", "explanation": "A resistor limits how much current flows. Placed in series with the LED, the 220 Ω one keeps the current gentle enough to light the LED instead of burning it out. The bands of colour print its value, and it has no direction." }, { "name": "Jumper wires", "imageAsset": "docs/course/assets/shared/item-jumper-wire.png", "explanation": "Jumper wires make temporary connections without soldering. Female-to-male wires have a socket on one end and a pin on the other, useful when a sensor module and board use different connector styles." }, { "name": "Arduino IDE", "imageAsset": "docs/course/assets/shared/item-arduino-ide.png", "explanation": "Arduino IDE is the desktop app that opens the sketch, compiles it, uploads it to the ESP32-S3, and shows messages from the board in Serial Monitor." } ], "wiring": [ { "partPin": "8 bar segments (via 220 Ω each)", "connectTo": "GPIO 21 47 38 39 40 41 42 2", "reason": "Each pin drives one segment with its own PWM channel." }, { "partPin": "Bar common row", "connectTo": "GND", "reason": "Returns every segment to zero volts." } ], "coachInstructions": [ "Start by confirming the Day 6 LED bar is still wired; only eight segments are driven today, and two staying dark is expected.", "Remind the learner that each driven segment needs its own 220 Ω series resistor — a shared or missing resistor is the common mistake here.", "If only one segment lights with no tail, suspect Day 6's on/off sketch is still loaded; have the learner upload 04.2 before changing anything else.", "If a segment in the path stays dark, check that segment's resistor and its jumper to its GPIO pin, not the whole circuit.", "Explain PWM, the dutys gradient, and the sliding window on request; do not dump theory before the learner has a working comet.", "Keep the Arduino path primary; MicroPython is optional only if already set up." ], "steps": [ "Confirm the Day 6 LED bar is still wired, or rebuild it — LED bar across the centre channel, one 220 Ω resistor per segment, common row to ground.", "Keep USB unplugged while you check or move any wire.", "Note that only eight segments are wired for PWM today, since the board has eight PWM channels; two segments stay dark on purpose.", "Compare every wire to the chart before you plug in USB.", "Open Sketch_04.2_FlowingLight2.ino in Arduino IDE and upload it.", "Watch a bright segment with a fading tail glide along the bar and back." ], "codeFocus": { "arduino": [ { "line": "ledcAttachChannel(ledPins[i], 1000, 10, chns[i])", "explanation": "Gives each of the eight pins its own PWM channel, so every segment can hold a brightness of its own." }, { "line": "const int dutys[] = {0,..., 1023,512,256,128,64,32,16,8, ...,0}", "explanation": "A brightness gradient — bright to dim — with dark padding on each side; those falling numbers are the fading tail." }, { "line": "ledcWrite(ledPins[j], dutys[i + j])", "explanation": "Reads an eight-wide window of the gradient and slides it one step each pass, which is what makes the comet move." } ], "micropython": [ { "line": "mypwm = myPWM(21,47,38,39,40,41,42,2)", "explanation": "A helper wraps each of the eight pins as a PWM object so they can hold brightness in Python." }, { "line": "dutys = [...1023,512,256,128,64,32,16,8...]", "explanation": "The same falling gradient as the Arduino sketch — the head is brightest and the tail fades." } ] }, "theoryModel": { "plainLanguage": "Give each LED its own brightness, shape a bright-to-dim gradient, then slide that gradient one step at a time so the head leads and the tail fades.", "formula": "eight brightnesses → a falling gradient → slide it one step → head leads, tail fades", "notes": [ { "title": "What PWM is doing", "body": "PWM flicks each pin on and off very fast; the fraction of time it stays on sets how bright that segment looks, so a whole row can carry a smooth gradient." } ] }, "test": { "expectedOutputExample": [ "A bright segment leads with dimmer segments trailing behind it.", "The bright head and its fading tail glide along the bar together.", "Then the comet slides back the other way, smoothly, for as long as the board has power." ], "successCriteria": "Two segments stay dark on purpose — only eight are on PWM, because the board has eight PWM channels." }, "troubleshooting": [ { "symptom": "Only one segment lights, with no tail", "firstChecks": [ "You may be running Day 6's on/off sketch — upload 04.2 so PWM sets the brightnesses." ] }, { "symptom": "A segment in the path stays dark", "firstChecks": [ "Check that segment's own 220 Ω resistor and its jumper to its GPIO pin." ] }, { "symptom": "Nothing lights at all", "firstChecks": [ "Re-check the common row to ground, then that the sketch uploaded." ] }, { "symptom": "Upload fails", "firstChecks": [ "Swap in a data-capable USB cable." ] } ], "challenge": "Change the trail by editing the dutys values, then change the sweep speed with the delay, and note what each edit does to the comet.", "logbookPrompts": [ "What did a longer or shorter tail change about how the comet looked?", "Which sweep speed felt best, and why?", "What real-world moving light works like this comet and tail?" ] }