Getting started with M5Stack StickC S3: WiFi, OTA firmware updates, and a real-world sound level meter with Discord alerts. Progressive examples from hello world to production.

1-README.md

M5StickC S3: Getting Started

Progressive guide from hello world to over-the-air updates to a real sound meter app.

Hardware

M5Stack StickC S3 (not the original StickC — different chip, display, and pinout)

• ESP32-S3
• 135×240 TFT LCD
• Built-in PDM microphone
• Built-in battery

Software Setup (Mac)

Install arduino-cli via Homebrew:

brew install arduino-cli

Add M5Stack board support:

arduino-cli config init
arduino-cli config add board_manager.additional_urls https://m5stack.oss-cn-shenzhen.aliyuncs.com/resource/arduino/package_m5stack_index.json
arduino-cli core update-index
arduino-cli core install m5stack:esp32

Install libraries:

arduino-cli lib install "M5Unified"

FQBN: m5stack:esp32:m5stack_sticks3

First Flash (USB — required once)

The device needs one USB flash to get ArduinoOTA onto it. After that, all updates are wireless.

1. Put device in bootloader mode: hold the side button + tap the reset button until the screen goes black
2. Connect USB-C
3. Find the port: arduino-cli board list
4. Flash:

arduino-cli compile --fqbn m5stack:esp32:m5stack_sticks3 --build-path /tmp/m5-build ./hello-world-ota/
arduino-cli upload -p /dev/cu.usbmodem101 --fqbn m5stack:esp32:m5stack_sticks3 /tmp/m5-build/

OTA Updates (all subsequent flashes)

Once the hello world sketch is running, get the IP from the screen, then:

arduino-cli compile --fqbn m5stack:esp32:m5stack_sticks3 --build-path /tmp/m5-build ./your-sketch/

python3 ~/Library/Arduino15/packages/m5stack/hardware/esp32/3.3.7/tools/espota.py \
  -i YOUR_DEVICE_IP -p 3232 \
  -f /tmp/m5-build/your-sketch.ino.bin

The IP shows at the bottom of the display after WiFi connects. You can also ping your-hostname.local from a Mac to find it.

Notes

• The .ino filename must match the folder name (Arduino requirement)
• Always use uint16_t for display colors — uint32_t uses the wrong color path
• espota.py path varies by ESP32 core version — check ~/Library/Arduino15/packages/m5stack/hardware/esp32/

2-hello-world-ota.ino

#include <M5Unified.h>
#include <WiFi.h>
#include <ArduinoOTA.h>

const char* WIFI_SSID = "Your WiFi Name";
const char* WIFI_PASS = "Your WiFi Password";

void setup() {
  auto cfg = M5.config();
  M5.begin(cfg);
  M5.Lcd.setRotation(1);   // landscape
  M5.Lcd.fillScreen(TFT_BLACK);
  M5.Lcd.setTextColor(TFT_WHITE);
  M5.Lcd.setTextSize(2);
  M5.Lcd.setCursor(10, 50);
  M5.Lcd.print("Connecting...");

  WiFi.begin(WIFI_SSID, WIFI_PASS);
  int tries = 0;
  while (WiFi.status() != WL_CONNECTED && tries++ < 20) delay(500);

  M5.Lcd.fillScreen(TFT_BLACK);

  if (WiFi.status() == WL_CONNECTED) {
    ArduinoOTA.setHostname("m5sticks3");
    ArduinoOTA.begin();

    M5.Lcd.setTextSize(3);
    M5.Lcd.setTextColor(TFT_GREEN);
    M5.Lcd.setCursor(20, 20);
    M5.Lcd.print("Hello!");

    M5.Lcd.setTextSize(1);
    M5.Lcd.setTextColor(TFT_WHITE);
    M5.Lcd.setCursor(4, 122);
    M5.Lcd.print(WiFi.localIP().toString());
  } else {
    M5.Lcd.setTextColor(TFT_RED);
    M5.Lcd.setTextSize(2);
    M5.Lcd.setCursor(10, 50);
    M5.Lcd.print("WiFi failed");
  }
}

void loop() {
  ArduinoOTA.handle();
  M5.update();
}

3-clubhouse-db-meter.ino

// Clubhouse dB Meter — Indy Hall
// M5Stack StickC S3 sound level monitor
//
// Features:
//   - Live dB metering with smoothing
//   - Segmented VU bar (50–100 dB), color-coded OK/LOUD/TOO LOUD
//   - Peak hold with white tick
//   - Discord webhook alerts when sustained loud (3+ samples at ≥92 dB)
//   - ThingSpeak logging every 5 minutes
//   - BtnA menu: click to open/cycle, hold to confirm
//   - Power Off menu item
//   - OTA firmware updates via ArduinoOTA

#include <M5Unified.h>
#include <WiFi.h>
#include <HTTPClient.h>
#include <ArduinoOTA.h>
#include <cmath>

const char* WIFI_SSID    = "Your WiFi Name";
const char* WIFI_PASS    = "Your WiFi Password";
const char* DISCORD_HOOK = "https://discord.com/api/webhooks/YOUR_WEBHOOK_ID/YOUR_WEBHOOK_TOKEN";
const char* THINGSPEAK_KEY = "YOUR_THINGSPEAK_KEY";

#define THRESHOLD_WARN     85
#define THRESHOLD_ALERT    92
#define BAR_DB_MIN         50
#define SAMPLE_SIZE        512
#define LOG_INTERVAL_MS    300000
#define SAMPLE_INTERVAL_MS 500
#define PEAK_HOLD_MS       3000
#define ALERT_COOLDOWN_MS  60000
#define BRIGHTNESS_DIM     64
#define BRIGHTNESS_IDLE    20
#define BRIGHTNESS_FULL    255
#define IDLE_TIMEOUT_MS    30000

// Display (landscape): 240×135
#define LCD_W    240
#define LCD_H    135
#define BAR_X    4
#define BAR_Y    60
#define BAR_W    (LCD_W - 8)   // 232
#define BAR_H    40
#define N_SEGS   46
#define SEG_W    4
#define SEG_GAP  1

int16_t mic_buf[SAMPLE_SIZE];
unsigned long lastAlert     = 0;
unsigned long lastLog       = 0;
unsigned long lastSample    = 0;
unsigned long lastWifiCheck = 0;
unsigned long lastChangeMs  = 0;
float smoothDb              = 0;
float lastDisplayDb         = -1;
float peakDb                = 0;
unsigned long peakTime      = 0;
int  prevStatus             = -1;    // -1=unset, 0=OK, 1=WARN, 2=ALERT

// Menu
#define MENU_TIMEOUT_MS  5000
const char* MENU_LABELS[] = {"Power Off"};
const int   MENU_COUNT    = 1;
bool          menuActive   = false;
int           menuItem     = 0;
unsigned long menuOpenedAt = 0;

void drawVuBar(float db, uint16_t fg, uint16_t bg) {
  uint16_t darkGray = M5.Lcd.color565(40, 40, 40);
  uint16_t matGreen = M5.Lcd.color565(76, 175, 80);

  float range    = 100.0f - BAR_DB_MIN;
  int greenSegs  = (int)((THRESHOLD_WARN  - BAR_DB_MIN) / range * N_SEGS);
  int orangeSegs = (int)((THRESHOLD_ALERT - BAR_DB_MIN) / range * N_SEGS);
  int fillSegs   = constrain((int)((db - BAR_DB_MIN) / range * N_SEGS), 0, N_SEGS);
  int peakSeg    = (peakDb > db && peakDb > BAR_DB_MIN)
                     ? constrain((int)((peakDb - BAR_DB_MIN) / range * N_SEGS), 0, N_SEGS - 1)
                     : -1;

  M5.Lcd.drawRect(BAR_X - 1, BAR_Y - 1, BAR_W + 2, BAR_H + 2, fg);

  // Paint every segment filled or dark — no full-region clear
  for (int i = 0; i < N_SEGS; i++) {
    int sx = BAR_X + 2 + i * (SEG_W + SEG_GAP);
    uint16_t c;
    if (i == peakSeg)      c = TFT_WHITE;
    else if (i < fillSegs) c = (i < greenSegs) ? matGreen : (i < orangeSegs) ? TFT_ORANGE : TFT_RED;
    else                   c = darkGray;
    M5.Lcd.fillRect(sx, BAR_Y + 2, SEG_W, BAR_H - 4, c);
  }

  // Threshold markers below bar
  int twarnX    = BAR_X + 2 + (int)((THRESHOLD_WARN  - BAR_DB_MIN) / range * N_SEGS) * (SEG_W + SEG_GAP) + SEG_W / 2;
  int talertX   = BAR_X + 2 + (int)((THRESHOLD_ALERT - BAR_DB_MIN) / range * N_SEGS) * (SEG_W + SEG_GAP) + SEG_W / 2;
  int tickY     = BAR_Y + BAR_H + 2;
  int lblY      = tickY + 4;

  M5.Lcd.drawFastVLine(twarnX,  tickY, 3, fg);
  M5.Lcd.drawFastVLine(talertX, tickY, 3, fg);

  M5.Lcd.setTextSize(1);
  M5.Lcd.setTextColor(fg, bg);
  M5.Lcd.setCursor(twarnX  - 6, lblY);
  M5.Lcd.print(THRESHOLD_WARN);
  M5.Lcd.setCursor(talertX - 6, lblY);
  M5.Lcd.print(THRESHOLD_ALERT);
}

void updateDisplay(float db) {
  uint16_t bg;
  uint16_t fg = TFT_WHITE;
  const char* label;
  int status;

  if (db >= THRESHOLD_ALERT) {
    status = 2; bg = TFT_RED; label = "TOO LOUD";
    M5.Lcd.setBrightness(BRIGHTNESS_FULL);
  } else if (db >= THRESHOLD_WARN) {
    status = 1; bg = TFT_ORANGE; fg = TFT_BLACK; label = "LOUD";
    M5.Lcd.setBrightness(BRIGHTNESS_FULL);
  } else {
    status = 0; bg = M5.Lcd.color565(76, 175, 80); label = "OK";
    unsigned long idle = millis() - lastChangeMs;
    M5.Lcd.setBrightness(idle > IDLE_TIMEOUT_MS ? BRIGHTNESS_IDLE : BRIGHTNESS_DIM);
  }

  bool statusChanged = (status != prevStatus);

  if (status == 2 && prevStatus != 2) {
    M5.Lcd.fillScreen(TFT_WHITE); delay(100);
    M5.Lcd.fillScreen(TFT_BLACK); delay(100);
  }
  prevStatus = status;

  if (statusChanged) {
    M5.Lcd.fillScreen(bg);
  } else {
    M5.Lcd.fillRect(0, 0, LCD_W, 57, bg);
    M5.Lcd.fillRect(0, 115, LCD_W, LCD_H - 115, bg);
  }

  M5.Lcd.setTextColor(fg, bg);

  // Number (textSize 6: 36px/char wide, 48px tall) + label (textSize 2: 12px/char wide, 16px tall)
  // drawn together, horizontally centered as a unit
  char dbStr[8];
  sprintf(dbStr, "%.0f", db);
  int numW  = strlen(dbStr) * 36;
  int lblW  = strlen(label) * 12;
  int unitW = numW + 10 + lblW;
  int startX = (LCD_W - unitW) / 2;

  M5.Lcd.setTextSize(6);
  M5.Lcd.setCursor(startX, 5);
  M5.Lcd.print(dbStr);

  // Label vertically centered within the number's 48px height
  M5.Lcd.setTextSize(2);
  M5.Lcd.setCursor(startX + numW + 10, 5 + 16);
  M5.Lcd.print(label);

  // VU meter bar
  drawVuBar(db, fg, bg);

  // Bottom info row (textSize 1: 6px/char wide, 8px tall)
  M5.Lcd.setTextSize(1);
  M5.Lcd.setTextColor(fg, bg);

  M5.Lcd.setCursor(BAR_X, 122);
  M5.Lcd.print(WiFi.localIP().toString());

  // Cooldown countdown centered
  unsigned long alertAge = millis() - lastAlert;
  if (lastAlert > 0 && alertAge < ALERT_COOLDOWN_MS) {
    char cdStr[12];
    sprintf(cdStr, "cd:%ds", (int)((ALERT_COOLDOWN_MS - alertAge) / 1000 + 1));
    int cdW = strlen(cdStr) * 6;
    M5.Lcd.setCursor((LCD_W - cdW) / 2, 122);
    M5.Lcd.print(cdStr);
  }

  // Battery right-aligned
  int bat = M5.Power.getBatteryLevel();
  String batStr = (M5.Power.isCharging() ? "+" : "") + String(bat) + "%";
  M5.Lcd.setCursor(LCD_W - batStr.length() * 6 - BAR_X, 122);
  M5.Lcd.print(batStr);
}

void drawMenu() {
  int bx = 30, by = 30, bw = 180, bh = 75;
  M5.Lcd.fillRoundRect(bx, by, bw, bh, 6, TFT_BLACK);
  M5.Lcd.drawRoundRect(bx, by, bw, bh, 6, TFT_WHITE);

  M5.Lcd.setTextSize(1);
  M5.Lcd.setTextColor(TFT_YELLOW, TFT_BLACK);
  M5.Lcd.setCursor(bx + 6, by + 6);
  M5.Lcd.print("MENU");

  for (int i = 0; i < MENU_COUNT; i++) {
    M5.Lcd.setTextColor(i == menuItem ? TFT_BLACK : TFT_WHITE,
                        i == menuItem ? TFT_WHITE  : TFT_BLACK);
    M5.Lcd.setCursor(bx + 8, by + 22 + i * 14);
    M5.Lcd.print(i == menuItem ? "> " : "  ");
    M5.Lcd.print(MENU_LABELS[i]);
  }

  M5.Lcd.setTextColor(M5.Lcd.color565(120, 120, 120), TFT_BLACK);
  M5.Lcd.setCursor(bx + 6, by + bh - 14);
  M5.Lcd.print("click:cycle  hold:select");
}

void executeMenuItem(int item) {
  if (item == 0) {
    M5.Lcd.fillScreen(TFT_BLACK);
    M5.Lcd.setTextColor(TFT_WHITE);
    M5.Lcd.setTextSize(2);
    M5.Lcd.setCursor(60, 55);
    M5.Lcd.print("Bye!");
    delay(800);
    M5.Power.powerOff();
  }
}

void sendDiscordAlert(float db) {
  if (millis() - lastAlert < ALERT_COOLDOWN_MS) return;
  HTTPClient http;
  http.begin(DISCORD_HOOK);
  http.addHeader("Content-Type", "application/json");
  String body = "{\"content\":\"Clubhouse sound alert: " + String((int)db) + " dB — too loud!\"}";
  http.POST(body);
  http.end();
  lastAlert = millis();
}

void logToThingSpeak(float db) {
  unsigned long now = millis();
  if (now - lastLog < LOG_INTERVAL_MS) return;
  lastLog = now;
  HTTPClient http;
  String url = String("https://api.thingspeak.com/update?api_key=") + THINGSPEAK_KEY + "&field1=" + String(db, 1);
  http.begin(url);
  http.GET();
  http.end();
}

void setup() {
  auto cfg = M5.config();
  cfg.internal_mic = true;
  M5.begin(cfg);
  M5.Lcd.setRotation(1);
  M5.Lcd.fillScreen(TFT_BLACK);
  M5.Lcd.setTextColor(TFT_WHITE);
  M5.Lcd.setTextSize(2);
  M5.Lcd.setCursor(8, 50);
  M5.Lcd.print("Connecting...");

  WiFi.begin(WIFI_SSID, WIFI_PASS);
  int tries = 0;
  while (WiFi.status() != WL_CONNECTED && tries++ < 20) delay(500);

  ArduinoOTA.setHostname("clubhouse-db-meter");
  ArduinoOTA.begin();

  M5.Mic.begin();
  lastLog      = millis();
  lastChangeMs = millis();
}

void loop() {
  ArduinoOTA.handle();
  M5.update();

  // Button: click opens/cycles menu, hold confirms selection
  if (M5.BtnA.wasClicked()) {
    if (!menuActive) {
      menuActive   = true;
      menuItem     = 0;
      menuOpenedAt = millis();
      prevStatus   = -1;   // force full redraw when menu closes
      drawMenu();
    } else {
      menuItem     = (menuItem + 1) % MENU_COUNT;
      menuOpenedAt = millis();
      drawMenu();
    }
  }
  if (M5.BtnA.wasHold() && menuActive) {
    menuActive = false;
    executeMenuItem(menuItem);
  }
  // Auto-dismiss after timeout
  if (menuActive && millis() - menuOpenedAt > MENU_TIMEOUT_MS) {
    menuActive = false;
    prevStatus = -1;
  }

  // WiFi self-heal
  if (millis() - lastWifiCheck > 30000) {
    lastWifiCheck = millis();
    if (WiFi.status() != WL_CONNECTED) WiFi.reconnect();
  }

  if (!menuActive && millis() - lastSample >= SAMPLE_INTERVAL_MS && M5.Mic.record(mic_buf, SAMPLE_SIZE, 16000)) {
    lastSample = millis();
    float sum = 0;
    for (int i = 0; i < SAMPLE_SIZE; i++) sum += (float)mic_buf[i] * mic_buf[i];
    float raw = 20.0f * log10f(sqrtf(sum / SAMPLE_SIZE) + 1.0f);

    smoothDb = (smoothDb == 0) ? raw : (0.7f * smoothDb + 0.3f * raw);

    // Peak hold
    if (smoothDb >= peakDb) {
      peakDb   = smoothDb;
      peakTime = millis();
    } else if (millis() - peakTime > PEAK_HOLD_MS) {
      peakDb = smoothDb;
    }

    if (fabsf(smoothDb - lastDisplayDb) >= 1.0f) {
      lastChangeMs  = millis();
      updateDisplay(smoothDb);
      lastDisplayDb = smoothDb;
    }

    if (smoothDb >= THRESHOLD_ALERT) sendDiscordAlert(smoothDb);
    logToThingSpeak(smoothDb);
  }
}