{ "schema": "tinyskiff.lessonPacket.v0", "lessonCode": "TSK-DAY28-BTLED", "course": "TinySkiff ESP32-S3 Lab", "day": 28, "title": "Switch an LED from your phone", "status": "published", "learnerProfile": "adult beginner; curious and capable; no electronics assumed", "estimatedTimeMinutes": 25, "mission": "Wire one LED to GPIO 2, upload the Bluetooth sketch, and switch the light from your phone — write led_on and led_off in LightBlue and watch the board obey a command sent over the air.", "mainPath": "Arduino/C++", "optionalSidePath": "MicroPython", "sourceMetadata": { "officialPdf": "source/Freenove_Super_Starter_Kit_for_ESP32_S3-main/C/C_Tutorial.pdf", "chapter": "Chapter 20 Bluetooth", "page": 193, "arduinoSketch": "source/Freenove_Super_Starter_Kit_for_ESP32_S3-main/C/Sketches/Sketch_20.2_BluetoothToLed/Sketch_20.2_BluetoothToLed.ino", "micropythonFile": "source/Freenove_Super_Starter_Kit_for_ESP32_S3-main/Python/Python_Codes/19.2_BLE_LED/BLE_LED.py", "imageAsset": "docs/course/assets/day-28/circuit-page-193.png", "imageAlt": "Official Freenove circuit for Bluetooth Control LED: a single LED on GPIO 2 through a 220 ohm resistor 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", "imageAsset": "docs/course/assets/shared/item-led.png", "explanation": "A LED is a one-way light. It only lights when its longer leg (the +) faces the pin and its shorter leg (the −) faces ground. Too much current burns it out, so a LED always sits behind a resistor." }, { "name": "220 Ω resistor", "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": "2 jumper wires (M/M)", "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": "LED long leg (+)", "connectTo": "GPIO 2 via 220 Ω", "reason": "This pin obeys the command your phone sends." }, { "partPin": "LED short leg (−)", "connectTo": "GND", "reason": "Completes the LED's path back to zero volts." } ], "coachInstructions": [ "Guide one physical step at a time and wait for learner confirmation before proceeding.", "The commands are led_on and led_off with underscores, written as utf-string; the manual's captions show hyphens and are wrong — always follow the code, never print the hyphen form.", "If the LED never reacts, check Serial Monitor at 115200 first — an echoed command with a dark LED points at wiring on GPIO 2; no echo points at the phone side or the spelling.", "If the LED is wired but dead, confirm long leg to GPIO 2 through the 220 Ω resistor and short leg to GND before changing code.", "If the phone can't find the board, repeat Day 27's LightBlue connection steps and have the learner press reset before reconnecting.", "Keep the Arduino path primary; the MicroPython version broadcasts as ESP32S3 and matches each command byte-for-byte, so expect those two differences." ], "steps": [ "Seat the ESP32-S3 on the GPIO extension board and keep USB unplugged while you wire.", "Place the LED so its long leg (+) is on the GPIO 2 side and its short leg (−) heads toward ground.", "Put the 220 Ω resistor in series between GPIO 2 and the LED's long leg.", "Compare every wire to the chart, then plug in USB.", "Open Sketch_20.2_BluetoothToLed.ino in Arduino IDE and upload it.", "Open Serial Monitor at 115200 and look for the \"device started\" line.", "On your phone, open LightBlue and connect to ESP32S3_Bluetooth, exactly as you did on Day 27.", "Find the write characteristic, set the format to utf-string, and write led_on — underscore, exact spelling.", "Watch the LED light, then write led_off to put it out." ], "codeFocus": { "arduino": [ { "line": "setupBLE(\"ESP32S3_Bluetooth\")", "explanation": "The same radio setup as Day 27 — the board advertises under the same name, with the same service underneath." }, { "line": "strncmp(rxload, \"led_on\", 6) == 0", "explanation": "True when the first six characters the phone wrote spell led_on — underscore included. The buffer rxload holds whatever landed in the write characteristic." }, { "line": "digitalWrite(LED, HIGH)", "explanation": "The matched command drives GPIO 2 HIGH and the LED lights; led_off drives it LOW again." }, { "line": "Serial.println(rxload)", "explanation": "Echoes every received command to Serial Monitor, so you can watch the words arrive as the LED obeys." } ], "micropython": [ { "line": "rx_data == b'led_on'", "explanation": "Compares the received bytes to the exact command — every character must match, where the Arduino sketch checks only the front of the buffer." }, { "line": "led.value(1)", "explanation": "Drives GPIO 2 HIGH and the LED lights." } ] }, "theoryModel": { "plainLanguage": "The board reads whatever arrived, compares it to two known words, and acts — the shape of every command protocol.", "formula": "phone text → match a known command → digitalWrite", "notes": [ { "title": "Why spelling is the whole protocol", "body": "The board compares raw characters. led_on with an underscore is a command; anything else is just text that scrolls past, and the LED holds its state." }, { "title": "What the radio adds", "body": "BLE only carries the bytes. The meaning — which words count as commands and what they do — lives entirely in the sketch you wrote." } ] }, "test": { "expectedOutputExample": [ "Write led_on in LightBlue (utf-string format) — the LED lights.", "Write led_off — the LED goes dark.", "Any other text leaves the LED exactly as it was — the sketch only acts on its two known commands." ], "successCriteria": "Serial Monitor at 115200 shows \"The device started, now you can pair it with Bluetooth!\" on boot, then echoes every command the board receives." }, "troubleshooting": [ { "symptom": "LED never reacts", "firstChecks": [ "Send the underscore spelling led_on exactly, in utf-string format." ] }, { "symptom": "LED wired but dead", "firstChecks": [ "Long leg to GPIO 2 through the 220 Ω resistor, short leg to GND." ] }, { "symptom": "Can't find the board", "firstChecks": [ "Repeat Day 27's LightBlue steps, and press reset before reconnecting." ] }, { "symptom": "Monitor blank", "firstChecks": [ "Set the baud rate to 115200." ] } ], "challenge": "Add a third command that blinks the LED twice, rename the commands to your own words, and note the exact spelling discipline a protocol demands.", "logbookPrompts": [ "What did your third command do, and what did you name it?", "What happened when a command was off by a single character?", "What device in your life is obeying exact spellings like this right now?" ] }