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Code snippet repository

C++ code library

Tested, reusable examples to speed up industrial ESP32 firmware development.

Wi-FiArduino (cpp)

Non-blocking automatic Wi-Fi reconnection

Manages the ESP32 Wi-Fi connection asynchronously, restoring the signal without interrupting the main loop.

code.cpp

cpp

1	#include <WiFi.h>
2
3	const char* SSID = "REDE_INDUSTRIAL";
4	const char* PASSWORD = "SENHA_INDUSTRIAL";
5	unsigned long lastWifiCheck = 0;
6
7	void handleWiFi() {
8	if (WiFi.status() != WL_CONNECTED) {
9	if (millis() - lastWifiCheck > 10000) {
10	lastWifiCheck = millis();
11	Serial.println("[Wi-Fi] Tentando reconectar...");
12	WiFi.disconnect();
13	WiFi.reconnect();
14	}
15	}
16	}
17
18	void setup() {
19	Serial.begin(115200);
20	WiFi.mode(WIFI_STA);
21	WiFi.begin(SSID, PASSWORD);
22	}
23
24	void loop() {
25	handleWiFi();
26	// Seu código de automação continua rodando sem travar
27	}

27 lines of C++

MQTTArduino (cpp)

Publishing JSON MQTT telemetry with PubSubClient

Builds a structured JSON payload with ArduinoJson and sends it periodically to an MQTT broker.

code.cpp

cpp

1	#include <WiFi.h>
2	#include <PubSubClient.h>
3	#include <ArduinoJson.h>
4
5	WiFiClient espClient;
6	PubSubClient client(espClient);
7
8	void publishTelemetry(float temp, float pressao, int pecas) {
9	JsonDocument doc;
10	doc["dev_id"] = "ESP32_GW01";
11	doc["temperatura"] = temp;
12	doc["pressao_bar"] = pressao;
13	doc["pecas_totais"] = pecas;
14	doc["uptime_ms"] = millis();
15
16	char buffer[256];
17	size_t length = serializeJson(doc, buffer, sizeof(buffer));
18	if (client.connected() && length > 0 && length < sizeof(buffer)) {
19	client.publish(
20	"industria/setor1/prensa01/telemetria",
21	reinterpret_cast<const uint8_t*>(buffer),
22	length
23	);
24	}
25	}

25 lines of C++

ModbusArduino (cpp)

Reading Modbus RTU master registers over RS-485

Configures Serial2 and performs non-blocking reads of Holding registers (0x03) with the ModbusRTU library.

code.cpp

cpp

1	#include <ModbusRTU.h>
2
3	#define RX2_PIN 16
4	#define TX2_PIN 17
5	#define DE_RE_PIN 4
6
7	ModbusRTU mb;
8	uint16_t res[4];
9
10	bool cbRead(Modbus::ResultCode event, uint16_t transactionId, void* data) {
11	if (event == Modbus::EX_SUCCESS) {
12	Serial.printf("Tensoes lidas: L1=%d, L2=%d, L3=%d\n", res[0], res[1], res[2]);
13	}
14	return true;
15	}
16
17	void setupModbus() {
18	Serial2.begin(9600, SERIAL_8N1, RX2_PIN, TX2_PIN);
19	mb.begin(&Serial2, DE_RE_PIN);
20	mb.master();
21	}
22
23	void readSlave() {
24	if (!mb.slave()) {
25	mb.readHreg(1, 0x0001, res, 3, cbRead);
26	}
27	mb.task();
28	}

28 lines of C++

RS-485Arduino (cpp)

RS-485 direction control (transmit/receive)

Switches the RS-485 transceiver DE/RE pin between transmit and receive modes.

code.cpp

cpp

1	#define DE_RE_PIN 4
2
3	void setupRS485Direction() {
4	pinMode(DE_RE_PIN, OUTPUT);
5	digitalWrite(DE_RE_PIN, LOW); // Inicia em recepção
6	}
7
8	void setRS485Transmit() {
9	digitalWrite(DE_RE_PIN, HIGH);
10	delayMicroseconds(10);
11	}
12
13	void setRS485Receive() {
14	Serial2.flush(); // Garante envio dos bytes acumulados
15	digitalWrite(DE_RE_PIN, LOW);
16	}

16 lines of C++

Web ServerArduino (cpp)

ESPAsyncWebServer with WebSockets for real-time state

A high-speed embedded web server that sends instantaneous data to the client browser.

code.cpp

cpp

1	#include <WiFi.h>
2	#include <ESPAsyncWebServer.h>
3
4	AsyncWebServer server(80);
5	AsyncWebSocket ws("/ws");
6
7	void onEvent(AsyncWebSocket server, AsyncWebSocketClient client, AwsEventType type, void arg, uint8_t data, size_t len) {
8	if (type == WS_EVT_CONNECT) {
9	client->text("{\"status\":\"CONECTADO_ESP32\"}");
10	}
11	}
12
13	void setupServer() {
14	ws.onEvent(onEvent);
15	server.addHandler(&ws);
16	server.begin();
17	}

17 lines of C++

OTAArduino (cpp)

ArduinoOTA setup for wireless flashing

Initializes the OTA firmware update service with a security password.

code.cpp

cpp

1	#include <WiFi.h>
2	#include <ArduinoOTA.h>
3
4	void setupOTA() {
5	ArduinoOTA.setHostname("esp32-node-01");
6	ArduinoOTA.setPassword("TROQUE_POR_UMA_SENHA_FORTE");
7	ArduinoOTA.onStart([]() { Serial.println("Iniciando OTA..."); });
8	ArduinoOTA.begin();
9	}
10
11	void handleOTA() {
12	ArduinoOTA.handle(); // Chame continuamente dentro de loop()
13	}

13 lines of C++

Inputs and outputsArduino (cpp)

Digital input interrupt with software debounce

Accurately counts industrial sensor pulses with interrupts and rejects noise-induced false triggers.

code.cpp

cpp

1	#define SENSOR_PIN 18
2	volatile unsigned long pulseCount = 0;
3	volatile uint32_t lastPulseUs = 0;
4
5	void IRAM_ATTR sensorISR() {
6	uint32_t now = micros();
7	if (now - lastPulseUs >= 50000) { // 50 ms; ajuste à frequência máxima do sensor
8	pulseCount++;
9	lastPulseUs = now;
10	}
11	}
12
13	void setupInterrupt() {
14	pinMode(SENSOR_PIN, INPUT_PULLUP);
15	attachInterrupt(digitalPinToInterrupt(SENSOR_PIN), sensorISR, FALLING);
16	}

16 lines of C++

SensorsArduino (cpp)

Reading a 4–20 mA sensor with ADS1115 I2C

High-precision differential analog reading (16-bit) for pressure and temperature transmitters.

code.cpp

cpp

1	#include <Wire.h>
2	#include <Adafruit_ADS1X15.h>
3
4	Adafruit_ADS1115 ads;
5
6	bool setupADC() {
7	ads.setGain(GAIN_ONE); // 1x gain +/- 4.096V
8	return ads.begin();
9	}
10
11	float readCurrentmA() {
12	int16_t adc0 = ads.readADC_SingleEnded(0);
13	float volts = ads.computeVolts(adc0);
14	// Resistor de 165 Ohms: 0,66 V a 3,30 V correspondem a 4 mA a 20 mA
15	float current_mA = (volts / 165.0) * 1000.0;
16	return current_mA;
17	}

17 lines of C++

WatchdogArduino (cpp)

ESP-IDF / Arduino Task Watchdog Timer (esp_task_wdt)

Configures the Task WDT to restart the ESP32 if a task remains stuck for more than five seconds.

code.cpp

cpp

1	#include <esp_task_wdt.h>
2	#include <esp_idf_version.h>
3
4	#define WDT_TIMEOUT 5 // 5 segundos
5
6	void setupWDT() {
7	#if ESP_IDF_VERSION_MAJOR >= 5
8	esp_task_wdt_config_t config = {
9	.timeout_ms = WDT_TIMEOUT * 1000,
10	.idle_core_mask = (1 << portNUM_PROCESSORS) - 1,
11	.trigger_panic = true
12	};
13	esp_err_t result = esp_task_wdt_init(&config);
14	if (result == ESP_ERR_INVALID_STATE) {
15	ESP_ERROR_CHECK(esp_task_wdt_reconfigure(&config));
16	} else {
17	ESP_ERROR_CHECK(result);
18	}
19	#else
20	esp_err_t result = esp_task_wdt_init(WDT_TIMEOUT, true);
21	if (result != ESP_ERR_INVALID_STATE) {
22	ESP_ERROR_CHECK(result);
23	}
24	#endif
25	ESP_ERROR_CHECK(esp_task_wdt_add(NULL)); // Adiciona a tarefa atual
26	}
27
28	void loop() {
29	esp_task_wdt_reset(); // Alimenta o cão de guarda
30	delay(1000);
31	}

31 lines of C++

StorageArduino (cpp)

Reading and writing JSON files with LittleFS

Stores and retrieves industrial settings in ESP32 flash memory without relying on EEPROM.

code.cpp

cpp

1	#include <LittleFS.h>
2	#include <ArduinoJson.h>
3
4	bool setupStorage() {
5	return LittleFS.begin(false); // Não formata automaticamente em caso de falha
6	}
7
8	bool saveConfig(const char* mqttServer, int port) {
9	File file = LittleFS.open("/config.json", FILE_WRITE);
10	if (!file) return false;
11
12	JsonDocument doc;
13	doc["server"] = mqttServer;
14	doc["port"] = port;
15
16	serializeJson(doc, file);
17	file.close();
18	return true;
19	}
20
21	bool loadConfig(String& mqttServer, int& port) {
22	File file = LittleFS.open("/config.json", FILE_READ);
23	if (!file) return false;
24
25	JsonDocument doc;
26	DeserializationError error = deserializeJson(doc, file);
27	file.close();
28	if (error \|\| !doc["server"].is<const char*>() \|\| !doc["port"].is<int>()) {
29	return false;
30	}
31
32	mqttServer = doc["server"].as<const char*>();
33	port = doc["port"].as<int>();
34	return true;
35	}

35 lines of C++

SecurityArduino (cpp)

Secure MQTTS connection with an SSL/TLS certificate

Configures WiFiClientSecure with a complete CA certificate for encrypted MQTT communication.

code.cpp

cpp

1	#include <WiFiClientSecure.h>
2	#include <PubSubClient.h>
3
4	// Substitua o trecho abaixo pelo certificado CA PEM completo do seu broker.
5	const char* CA_CERT =
6	"-----BEGIN CERTIFICATE-----\n"
7	"MIIDSjCCAjqgAwIBAgIQRK+og6vx7zgO77/29GHHzTANBgkqhkiG9w0BAQsFADBh\n"
8	"...\n"
9	"-----END CERTIFICATE-----\n";
10
11	WiFiClientSecure secureClient;
12	PubSubClient mqttClient(secureClient);
13
14	void setupSecureMQTT() {
15	secureClient.setCACert(CA_CERT);
16	mqttClient.setServer("broker.seudominio.com.br", 8883);
17	}

17 lines of C++

JSONArduino (cpp)

Parsing and validating input JSON over MQTT/Web

Receives and deserializes JSON commands while validating required fields.

code.cpp

cpp

1	#include <ArduinoJson.h>
2
3	void parseCommandPayload(const uint8_t* payload, size_t length) {
4	JsonDocument doc;
5	DeserializationError error = deserializeJson(doc, payload, length);
6
7	if (error) {
8	Serial.print("Falha ao ler JSON: ");
9	Serial.println(error.f_str());
10	return;
11	}
12
13	if (!doc["comando"].is<const char*>() \|\| !doc["valor"].is<int>()) {
14	Serial.println("JSON sem os campos obrigatórios ou com tipos inválidos");
15	return;
16	}
17
18	const char* cmd = doc["comando"].as<const char*>();
19	int valor = doc["valor"].as<int>();
20	Serial.printf("Executando comando: %s com valor %d\n", cmd, valor);
21	}

21 lines of C++