• MCU: ESP32-DEVKITC-32UE
• Framework: Arduino
• Build system: PlatformIO
• Key libraries: WiFi, HTTPClient

Ini
[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600
lib_deps =

Cpp
#include <Arduino.h>
#include <WiFi.h>
#include <HTTPClient.h>

static constexpr int MONEY_IN_PIN = 34;
static constexpr int MONEY_OUT_PIN = 35;
static constexpr int BOOT_PIN = 0;
static constexpr int STATUS_LED_PIN = 2;

static const char* WIFI_SSID = "YOUR_WIFI_SSID";
static const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD";
static const char* SERVER_URL = "http://YOUR_SERVER/api/slot-events";

volatile uint32_t moneyInPulses = 0;
volatile uint32_t moneyOutPulses = 0;
volatile uint32_t lastMoneyInUs = 0;
volatile uint32_t lastMoneyOutUs = 0;

uint32_t lastPublishMs = 0;
uint32_t lastWifiRetryMs = 0;

void IRAM_ATTR onMoneyInPulse() {
  const uint32_t now = micros();
  if (now - lastMoneyInUs > 2000) {
    moneyInPulses++;
    lastMoneyInUs = now;
  }
}

void IRAM_ATTR onMoneyOutPulse() {
  const uint32_t now = micros();
  if (now - lastMoneyOutUs > 2000) {
    moneyOutPulses++;
    lastMoneyOutUs = now;
  }
}

void connectWiFi() {
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to WiFi");
  for (int i = 0; i < 40 && WiFi.status() != WL_CONNECTED; ++i) {
    delay(250);
    Serial.print('.');
    digitalWrite(STATUS_LED_PIN, !digitalRead(STATUS_LED_PIN));
  }
  Serial.println();
  if (WiFi.status() == WL_CONNECTED) {
    Serial.print("Connected, IP = ");
    Serial.println(WiFi.localIP());
    digitalWrite(STATUS_LED_PIN, HIGH);
  } else {
    Serial.println("WiFi not connected, continuing offline");
    digitalWrite(STATUS_LED_PIN, LOW);
  }
}

void publishCounts(uint32_t inCount, uint32_t outCount) {
  if (WiFi.status() != WL_CONNECTED) {
    return;
  }

  HTTPClient http;
  http.begin(SERVER_URL);
  http.addHeader("Content-Type", "application/json");

  const String payload = String("{\"money_in\":") + inCount +
                         String(",\"money_out\":") + outCount + String("}");

  const int httpCode = http.POST(payload);
  Serial.print("POST result: ");
  Serial.println(httpCode);
  if (httpCode > 0) {
    Serial.println(http.getString());
  }
  http.end();
}

void setup() {
  pinMode(STATUS_LED_PIN, OUTPUT);
  digitalWrite(STATUS_LED_PIN, LOW);

  Serial.begin(115200);
  delay(200);
  Serial.println("Slot telemetry firmware starting");

  pinMode(MONEY_IN_PIN, INPUT);
  pinMode(MONEY_OUT_PIN, INPUT);
  pinMode(BOOT_PIN, INPUT);

  attachInterrupt(digitalPinToInterrupt(MONEY_IN_PIN), onMoneyInPulse, FALLING);
  attachInterrupt(digitalPinToInterrupt(MONEY_OUT_PIN), onMoneyOutPulse, FALLING);

  connectWiFi();
}

void loop() {
  const uint32_t nowMs = millis();

  if (WiFi.status() != WL_CONNECTED && (nowMs - lastWifiRetryMs) > 10000) {
    lastWifiRetryMs = nowMs;
    connectWiFi();
  }

  if ((nowMs - lastPublishMs) > 1000) {
    lastPublishMs = nowMs;

    noInterrupts();
    const uint32_t inSnapshot = moneyInPulses;
    const uint32_t outSnapshot = moneyOutPulses;
    interrupts();

    Serial.print("money_in=");
    Serial.print(inSnapshot);
    Serial.print(", money_out=");
    Serial.println(outSnapshot);

    publishCounts(inSnapshot, outSnapshot);
  }
}

• Build: pio run
• Flash: pio run -t upload
• Serial monitor: pio device monitor -b 115200
• Enter bootloader mode: hold the BOOT button, tap RESET, then release BOOT after upload starts.