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External API Reference

This page indexes the external ESP32 platform APIs commonly used alongside the M5Cardputer library. These are not part of M5Cardputer β€” click through to each library's official documentation for full API details.

WiFi

Library Source Key Classes / Functions
arduino-esp32 WiFi Documentation WiFi.begin(), WiFi.status(), WiFi.localIP(), WiFi.disconnect() 
#include <WiFi.h>
WiFi.begin("SSID", "password");
while (WiFi.status() != WL_CONNECTED) { delay(500); }

HTTP Client

Library Source Key Classes
HTTPClient Built into arduino-esp32 HTTPClient, begin(), GET(), POST(), getString() 
#include <HTTPClient.h>
HTTPClient http;
http.begin("http://example.com/api");
int code = http.GET();
String body = http.getString();
http.end();

Web Server

Library Source Key Classes
WebServer Built into arduino-esp32 WebServer, on(), send(), handleClient()

MQTT

Library Source Key Classes
PubSubClient GitHub PubSubClient, setServer(), connect(), publish(), subscribe(), loop()
AsyncMQTTClient GitHub Async, non-blocking alternative 
#include <PubSubClient.h>
WiFiClient wifiClient;
PubSubClient mqtt(wifiClient);
mqtt.setServer("broker.emqx.io", 1883);
mqtt.connect("cardputer");
mqtt.publish("topic/hello", "data");
mqtt.loop();

Bluetooth (BLE)

Library Source Key Classes
ESP32 BLE Arduino GitHub BLEDevice, BLEServer, BLECharacteristic, BLEAdvertising
NimBLE GitHub Lighter stack, lower RAM usage 
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>

USB HID

Library Source Key Classes
ESP32TinyUSB GitHub USBHID, keyboardReport(), mouseReport()
Arduino ESP32 USB Built-in for ESP32-S2/S3 USB.begin(), Keyboard.begin(), Keyboard.print() 
#include <USB.h>
#include <USBHIDKeyboard.h>
USBHIDKeyboard Keyboard;
Keyboard.begin();
Keyboard.print("Hello");

TinyUSB is used by the usbKeyboard example. See examples/Basic/keyboard/usbKeyboard.

SSH Client

Library Source Key Classes
LibSSH-ESP32 GitHub SSHClient, connect(), authenticate(), executeCommand()

Used by the SSHClient example. See examples/Advanced/SSHClient.

FreeRTOS (Multitasking)

Resource Link
ESP-IDF FreeRTOS Documentation 
TaskHandle_t taskHandle;
xTaskCreatePinnedToCore(
    myTask, "TaskName", 4096, NULL, 1, &taskHandle, 0
);

void myTask(void* param) {
    while (1) {
        // Do work
        vTaskDelay(10 / portTICK_PERIOD_MS);
    }
}

Warning

The M5Cardputer keyboard reader uses FreeRTOS features internally. Avoid creating tasks on core 0 pin if you use TCA8418KeyboardReader (ADV model) β€” the ISR runs there.

OTA Updates

Library Source
ArduinoOTA Built into arduino-esp32
ElegantOTA GitHub (Web UI-based) 
#include <ArduinoOTA.h>
ArduinoOTA.begin();
// In loop():
ArduinoOTA.handle();

JSON Parsing

Library Source Key Classes
ArduinoJson GitHub StaticJsonDocument, DynamicJsonDocument, deserializeJson(), serializeJson()

Performance & Debugging

Tool Purpose
ESP.getFreeHeap() Check free DRAM
ESP.getPsramSize() / ESP.getFreePsram() PSRAM info
ESP.getChipModel() / ESP.getChipCores() Chip info
esp_task_wdt_init() Watchdog timer
Serial.printf() Debug output

See Also