Pinouts

tinySniff uses the following tinyCore pins. These pins are in use whenever the HAT is mounted, so avoid assigning them to other peripherals in your own sketches.

Gas Sensors (Analog Input)

Signal	Pin	Sensor	Measures
H2S	`A0`	GM-602B	Hydrogen sulfide
CO	`A1`	GM-702B	Carbon monoxide
CH4	`A2`	GM-402B	Methane / combustible gas

Each sensor sits in a voltage divider, so reading one is a plain analogRead():

#define PIN_H2S  A0
#define PIN_CO   A1
#define PIN_CH4  A2

void setup() {
  analogReadResolution(12);   // 0 to 4095
  pinMode(PIN_H2S, INPUT);
  pinMode(PIN_CO,  INPUT);
  pinMode(PIN_CH4, INPUT);
}

void loop() {
  int h2s = analogRead(PIN_H2S);
}

The A0/A1/A2 aliases come from the tinyCore board library. Use them rather than raw GPIO numbers so your sketch stays portable across board revisions.

The ESP32-S3’s ADC jitters by several counts even on a perfectly steady input. The logger, sheets, and alarm demos all average 100 reads into one value:

float supersample(int pin) {
    long sum = 0;
    for (int i = 0; i < SUPERSAMPLE_COUNT; i++) sum += analogRead(pin);
    return (float)sum / SUPERSAMPLE_COUNT;
}

Random noise falls off as the square root of the sample count, so 100 reads is roughly 10x quieter than one. It costs about a millisecond.

Buzzer

Signal	Pin	Description
BUZZER	`13`	Digital pin 13

Pin 13 is labeled as a digital pin on the tinyCore, but every GPIO on the ESP32-S3 can do PWM, so tone() works here without any special setup:

#define PIN_BUZZER 13

pinMode(PIN_BUZZER, OUTPUT);
tone(PIN_BUZZER, 2600, 120);   // 2.6 kHz for 120 ms
noTone(PIN_BUZZER);            // silence it early

Button (Active-Low)

Signal	Pin	Description
BTN	`RX`	Active-low, internal pull-up enabled via `INPUT_PULLUP`

#define PIN_BUTTON RX

pinMode(PIN_BUTTON, INPUT_PULLUP);

if (digitalRead(PIN_BUTTON) == LOW) {
  // pressed
}

No external resistor is needed. The ESP32’s internal pull-up holds the pin HIGH, and pressing the button shorts it to GND.

Every demo debounces it the same way, because a mechanical switch bounces for a few milliseconds and would otherwise register as several presses:

int reading = digitalRead(PIN_BUTTON);
if (reading != lastButtonState) lastDebounceTime = millis();
if ((millis() - lastDebounceTime) > 50) {
    static int buttonState = HIGH;
    if (reading != buttonState) {
        buttonState = reading;
        if (buttonState == LOW) {
            // real press, act here
        }
    }
}
lastButtonState = reading;

The pattern is: note the moment the reading last changed, and only believe it once it has held still for 50 ms.

The RX pin doubles as the ESP32’s UART receive line. In practice this rarely causes trouble, since the button is open (HIGH) by default. Just avoid holding it down while uploading firmware.

Reserved Pins Summary

Pin	HAT Function	Notes
`A0`	H₂S sensor	Analog input, GM-602B
`A1`	CO sensor	Analog input, GM-702B
`A2`	CH₄ sensor	Analog input, GM-402B
`13`	Buzzer	Digital out / PWM via `tone()`
`RX`	Button	Active-low, internal pull-up

All other tinyCore pins stay available for your own use when the tinySniff HAT is mounted, including A3, A4, and A5, and the SD card interface that SD Card Logger uses.