Initial Code

.gitignore

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+.pio
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch

.vscode/extensions.json

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+{
+    // See http://go.microsoft.com/fwlink/?LinkId=827846
+    // for the documentation about the extensions.json format
+    "recommendations": [
+        "platformio.platformio-ide"
+    ],
+    "unwantedRecommendations": [
+        "ms-vscode.cpptools-extension-pack"
+    ]
+}

include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the convention is to give header files names that end with `.h'.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

lib/README

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+
+This directory is intended for project specific (private) libraries.
+PlatformIO will compile them to static libraries and link into the executable file.
+
+The source code of each library should be placed in a separate directory
+("lib/your_library_name/[Code]").
+
+For example, see the structure of the following example libraries `Foo` and `Bar`:
+
+|--lib
+|  |
+|  |--Bar
+|  |  |--docs
+|  |  |--examples
+|  |  |--src
+|  |     |- Bar.c
+|  |     |- Bar.h
+|  |  |- library.json (optional. for custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html
+|  |
+|  |--Foo
+|  |  |- Foo.c
+|  |  |- Foo.h
+|  |
+|  |- README --> THIS FILE
+|
+|- platformio.ini
+|--src
+   |- main.c
+
+Example contents of `src/main.c` using Foo and Bar:
+```
+#include <Foo.h>
+#include <Bar.h>
+
+int main (void)
+{
+  ...
+}
+
+```
+
+The PlatformIO Library Dependency Finder will find automatically dependent
+libraries by scanning project source files.
+
+More information about PlatformIO Library Dependency Finder
+- https://docs.platformio.org/page/librarymanager/ldf.html

platformio.ini

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+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:lilygo-t3-s3]
+platform = espressif32
+board = lilygo-t3-s3
+framework = arduino
+monitor_speed = 115200
+build_flags =
+    -D ARDUINO_USB_CDC_ON_BOOT=1
+lib_deps =
+    jgromes/RadioLib
+    adafruit/Adafruit SSD1306
+    adafruit/Adafruit GFX Library

src/main.cpp

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+#include <Arduino.h>
+#include <SPI.h>
+#include <Wire.h>
+#include <RadioLib.h>
+#include <Adafruit_GFX.h>
+#include <Adafruit_SSD1306.h>
+
+// =========================
+// LoRa pins - LilyGO T3S3 SX1262
+// =========================
+static const int PIN_LORA_SCK  = 5;
+static const int PIN_LORA_MISO = 3;
+static const int PIN_LORA_MOSI = 6;
+static const int PIN_LORA_CS   = 7;
+static const int PIN_LORA_RST  = 8;
+static const int PIN_LORA_DIO1 = 33;
+static const int PIN_LORA_BUSY = 34;
+
+// =========================
+// Button - LilyGO T3S3
+// BOOT button usually GPIO0, active low
+// =========================
+static const int PIN_BUTTON = 0;
+
+// =========================
+// OLED pins - LilyGO T3S3 OLED
+// =========================
+static const int OLED_SDA = 18;
+static const int OLED_SCL = 17;
+static const int OLED_ADDR = 0x3C;
+static const int SCREEN_WIDTH = 128;
+static const int SCREEN_HEIGHT = 64;
+
+// =========================
+// ACTIVE PROFILE - Shelly / custom LoRa
+// =========================
+static const float LORA_FREQ_MHZ      = 865.000;
+static const float LORA_BW_KHZ        = 125.0;
+static const uint8_t LORA_SF          = 12;
+static const uint8_t LORA_CR          = 5;
+static const uint8_t LORA_SYNC_WORD   = 0x12;
+static const int8_t  LORA_TX_POWER    = 10;
+static const uint16_t LORA_PREAMBLE   = 10;
+static const float LORA_TCXO_VOLTAGE  = 1.6;
+static const bool LORA_USE_LDO        = false;
+static const bool LORA_USE_CRC        = false;
+static const bool LORA_EXPLICIT_HDR   = true;
+
+// =========================
+// Protocol
+// =========================
+static const String DEVICE_ID = "MG64738";
+static const String CMD_ON    = "ON";
+static const String CMD_OFF   = "OF";
+
+// =========================
+// Objects
+// =========================
+Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
+SX1262 radio = new Module(PIN_LORA_CS, PIN_LORA_DIO1, PIN_LORA_RST, PIN_LORA_BUSY);
+
+// =========================
+// Runtime state
+// =========================
+bool outputState = true;       // start with ON
+bool lastButtonState = HIGH;
+unsigned long lastDebounceMs = 0;
+unsigned long txCount = 0;
+int lastTxState = 0;
+
+static const unsigned long DEBOUNCE_MS = 60;
+
+// =========================
+// Helpers
+// =========================
+String formatCR(uint8_t cr) {
+  return "4/" + String(cr);
+}
+
+String formatHexByte(uint8_t value) {
+  char buf[5];
+  snprintf(buf, sizeof(buf), "%02X", value);
+  return String(buf);
+}
+
+String currentPayload() {
+  return DEVICE_ID + "|" + (outputState ? CMD_ON : CMD_OFF);
+}
+
+void drawLine(int x, int y, const String& text) {
+  display.setCursor(x, y);
+  display.print(text);
+}
+
+void drawStatusScreen(const String& status) {
+  display.clearDisplay();
+  display.setTextSize(1);
+  display.setTextColor(SSD1306_WHITE);
+
+  drawLine(0, 0, "LoRa Button TX");
+  drawLine(88, 0, String(txCount) + " tx");
+
+  drawLine(0, 10, "F:" + String(LORA_FREQ_MHZ, 3));
+  drawLine(0, 20, "BW:" + String(LORA_BW_KHZ, 1) + " SF:" + String(LORA_SF));
+  drawLine(0, 30, "CR:" + formatCR(LORA_CR) + " SW:0x" + formatHexByte(LORA_SYNC_WORD));
+
+  drawLine(0, 42, status);
+  drawLine(0, 54, currentPayload());
+
+  display.display();
+}
+
+void drawErrorScreen(const String& title, int code) {
+  display.clearDisplay();
+  display.setTextSize(1);
+  display.setTextColor(SSD1306_WHITE);
+
+  drawLine(0, 0, title);
+  drawLine(0, 12, "code: " + String(code));
+
+  display.display();
+}
+
+void sendCurrentState() {
+  String payload = currentPayload();
+
+  drawStatusScreen("Sending...");
+
+  Serial.print("TX: ");
+  Serial.println(payload);
+
+  int state = radio.transmit(payload);
+  lastTxState = state;
+
+  if (state == RADIOLIB_ERR_NONE) {
+    txCount++;
+
+    Serial.println("TX OK");
+    drawStatusScreen(outputState ? "Sent ON" : "Sent OF");
+  } else {
+    Serial.print("TX failed, code ");
+    Serial.println(state);
+    drawStatusScreen("TX failed: " + String(state));
+  }
+}
+
+void setup() {
+  Serial.begin(115200);
+  delay(1500);
+
+  pinMode(PIN_BUTTON, INPUT_PULLUP);
+
+  Wire.begin(OLED_SDA, OLED_SCL);
+
+  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
+    Serial.println("OLED init failed");
+    while (true) delay(1000);
+  }
+
+  drawStatusScreen("Booting...");
+
+  SPI.begin(PIN_LORA_SCK, PIN_LORA_MISO, PIN_LORA_MOSI, PIN_LORA_CS);
+
+  Serial.println();
+  Serial.println("Starting LoRa button sender...");
+
+  int state = radio.begin(
+    LORA_FREQ_MHZ,
+    LORA_BW_KHZ,
+    LORA_SF,
+    LORA_CR,
+    LORA_SYNC_WORD,
+    LORA_TX_POWER,
+    LORA_PREAMBLE,
+    LORA_TCXO_VOLTAGE,
+    LORA_USE_LDO
+  );
+
+  if (state != RADIOLIB_ERR_NONE) {
+    Serial.print("radio.begin failed, code ");
+    Serial.println(state);
+    drawErrorScreen("LoRa init failed", state);
+    while (true) delay(1000);
+  }
+
+  if (LORA_EXPLICIT_HDR) {
+    state = radio.explicitHeader();
+  } else {
+    state = radio.implicitHeader(LORA_PREAMBLE);
+  }
+
+  if (state != RADIOLIB_ERR_NONE) {
+    Serial.print("header mode failed, code ");
+    Serial.println(state);
+    drawErrorScreen("Header config failed", state);
+    while (true) delay(1000);
+  }
+
+  state = radio.setCRC(LORA_USE_CRC);
+
+  if (state != RADIOLIB_ERR_NONE) {
+    Serial.print("CRC config failed, code ");
+    Serial.println(state);
+    drawErrorScreen("CRC config failed", state);
+    while (true) delay(1000);
+  }
+
+  drawStatusScreen("Ready");
+
+  sendCurrentState();   // first send = MG64738|ON
+}
+
+void loop() {
+  bool buttonState = digitalRead(PIN_BUTTON);
+
+  if (buttonState != lastButtonState) {
+    lastDebounceMs = millis();
+    lastButtonState = buttonState;
+  }
+
+  if ((millis() - lastDebounceMs) > DEBOUNCE_MS) {
+    static bool pressHandled = false;
+
+    if (buttonState == LOW && !pressHandled) {
+      pressHandled = true;
+
+      outputState = !outputState;
+      sendCurrentState();
+    }
+
+    if (buttonState == HIGH) {
+      pressHandled = false;
+    }
+  }
+}

test/README

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+
+This directory is intended for PlatformIO Test Runner and project tests.
+
+Unit Testing is a software testing method by which individual units of
+source code, sets of one or more MCU program modules together with associated
+control data, usage procedures, and operating procedures, are tested to
+determine whether they are fit for use. Unit testing finds problems early
+in the development cycle.
+
+More information about PlatformIO Unit Testing:
+- https://docs.platformio.org/en/latest/advanced/unit-testing/index.html