Lesson 2 of 4

The BOOT button and the chip's thermometer

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// BOOT button toggles the LED and prints the chip temperature const uint8_t BOOT_PIN = 0; // BOOT button (SW1) on GPIO0 const uint8_t LED_PIN = 4; const unsigned long DEBOUNCE_MS = 30; bool ledOn = false; int lastReading = HIGH; int stable = HIGH; unsigned long changedAt = 0; int presses = 0; void setup() { Serial.begin(115200); pinMode(BOOT_PIN, INPUT_PULLUP); // pressed = LOW, released = HIGH pinMode(LED_PIN, OUTPUT); Serial.println("press BOOT"); } void loop() { int reading = digitalRead(BOOT_PIN); if (reading != lastReading) { // the reading changed: restart the timer changedAt = millis(); lastReading = reading; } if (millis() - changedAt >= DEBOUNCE_MS && reading != stable) { stable = reading; if (stable == LOW) { // a clean press presses++; ledOn = !ledOn; digitalWrite(LED_PIN, ledOn ? HIGH : LOW); float chipC = temperatureRead(); // die temperature in °C Serial.printf("BOOT pressed #%d, chip %.1f C\n", presses, chipC); } } }

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BOOT is a strapping button at reset but an ordinary input afterwards. Read it with a debounce, toggle the LED and print the chip's own temperature sensor.

A real input with no extra parts
Debounce with millis(), never delay()
GPIO0 is a strapping pin at reset

Pin	Connects to	What it does
`GPIO0`	BOOT button SW1 (on the board)	Input with pull-up
`GPIO4`	330 Ω, then the LED	Digital output

Wire it in

Sensors and actuators this board drives, with the real connections.

All 10 parts on the ESP32-S3-DevKitC-1 page

The BOOT button and the chip's thermometer

Try it yourself

Serial monitor

Checks

Break it

Inputs

Parameters

Wire it in

The BOOT button and the chip's thermometer

Try it yourself

Serial monitor

Checks

Break it

Inputs

Parameters

Wire it in