Documentation

// Blink any breakout point to confirm your wiring & labels.
// Change TEST_PIN, upload, and put an LED (with resistor) or
// a multimeter on that terminal.
const int TEST_PIN = 27;

void setup() {
  pinMode(TEST_PIN, OUTPUT);
  Serial.begin(115200);
  Serial.printf("Toggling GPIO %d\n", TEST_PIN);
}

void loop() {
  digitalWrite(TEST_PIN, HIGH);
  delay(500);
  digitalWrite(TEST_PIN, LOW);
  delay(500);
}

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);   // SDA, SCL on the breakout's I2C points
}

void loop() {
  int found = 0;
  for (byte addr = 1; addr < 127; addr++) {
    Wire.beginTransmission(addr);
    if (Wire.endTransmission() == 0) {
      Serial.printf("Device at 0x%02X\n", addr);
      found++;
    }
  }
  if (!found) Serial.println("No I2C devices found - check SDA/SCL");
  Serial.println("---");
  delay(3000);
}

// Proof of the ADC rule: GPIO 34 (ADC1) keeps working with Wi-Fi on;
// an ADC2 pin (e.g. GPIO 25) would return zeros here.
#include <WiFi.h>

const int SENSOR = 34;   // input-only ADC1 pin on the breakout

void setup() {
  Serial.begin(115200);
  analogSetPinAttenuation(SENSOR, ADC_11db);
  WiFi.begin("YourNetwork", "YourPassword");   // Wi-Fi active
}

void loop() {
  int raw = analogRead(SENSOR);
  float volts = raw * (3.3 / 4095.0);
  Serial.printf("ADC1 raw: %d  (%.2f V)  WiFi: %s\n",
                raw, volts,
                WiFi.status() == WL_CONNECTED ? "connected" : "...");
  delay(500);
}

from machine import Pin
import time

# Pulses each safe output pin in turn - follow along with an LED
# probe on the breakout terminals to verify every label.
SAFE_PINS = [4, 5, 13, 14, 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 32, 33]

pins = [Pin(n, Pin.OUT, value=0) for n in SAFE_PINS]

while True:
    for n, p in zip(SAFE_PINS, pins):
        print("GPIO", n)
        p.value(1)
        time.sleep(0.4)
        p.value(0)
        time.sleep(0.1)