/*
File: Heltec_ESP32_LoRa_V3_Sevo_TX_AiRotaryEncoder.ino
written on 24 Jun, 2025 by Ahmad Shamshiri

 * =====================================================================
 * ARDUINO CODE DESCRIPTION: SECURE LoRa SERVO CONTROL SYSTEM (TX)
 * =====================================================================
 * 
 * HARDWARE COMPONENTS:
 * -------------------
 *  - Main Controller: Heltec WiFi LoRa 32 V3
 *  - Enclosure: Meshnology N33 case with 3000mAh battery
 *  - Input: Rotary encoder with push-button
 *  - Feedback: Built-in OLED display
 *  - Output: Servo motor + LoRa wireless transmission
 * 
 * SYSTEM FUNCTIONALITY:
 * -------------------
 * [1] ROTARY ENCODER CONTROL:
 *     - Clockwise/Counter-clockwise rotation adjusts target angle (0°-180°)
 *     - Real-time angle display on OLED screen
 *     - Push-button returns servo to Home position (default: 90°)
 * 
 * [2] SECURE WIRELESS TRANSMISSION:
 *     - All angle values encrypted before LoRa transmission
 *     - Home position command transmitted as special secure packet
 *     - Uses 433MHz LoRa band for reliable communication
 * 
 * [3] POWER MANAGEMENT:
 *     - Optimized for battery operation (3000mAh)
 *     - Low-power modes between transmissions
 * 
 * FOR COMPLETE SETUP INSTRUCTIONS:
 * Please watch the tutorial video at: https://youtu.be/EPynuJ7sasY
 * =====================================================================

Watch full video explaination:  https://youtu.be/EPynuJ7sasY
Resources page: https://robojax.com/T635


 * DISCLAIMER:
 * This code is provided "AS IS" without warranty of any kind. The author 
 * shall not be held liable for any damages arising from the use of this code.
 * 
 * LICENSE:
 * This work is licensed under the GNU General Public License v3.0 
 * Permissions beyond the scope of this license may be available at Robojax.com
 * 
 * SHARING TERMS:
 * You are free to share, copy and modify this code for non-commercial purposes
 * PROVIDED you:
 * 1. Keep this entire comment block intact with the original code
 * 2. Include the original Robojax.com link
 * 3. Keep the YouTube tutorial link (if applicable)
 * 4. Clearly indicate any modifications made
 * 
 * Original tutorial at: https://robojax.com/T635
 * YouTube Video: https://youtu.be/EPynuJ7sasY
 * 
 * ********************************************************************
 */

#include <Wire.h>               
#include "HT_SSD1306Wire.h"
#include "WiFi.h"
static SSD1306Wire  display(0x3c, 500000, SDA_OLED, SCL_OLED, GEOMETRY_128_64, RST_OLED); // addr , freq , i2c group , resolution , rst


const int TX_POWER = 2;//dBm from 2 to 20. when powered via battery 2 to 14dBm is the best option
const int MAX_ANGLE = 180;//the most common is 180, but you can set it as needed

String labelAngle = "Angle";
const int homePosition = 90; //initial position


//endcoder
const int SW_PIN = 4;//define a pin for rotary encode switch
const int PIN_A  = 6;
const int PIN_B  = 5;//
const int ANGLE_STEP  = 6;//
const bool debug= false;//to print debug data in serial moinitor set it to true, else false

int servoAngel = homePosition;
int oldAngleValue = servoAngel;
#include "mbedtls/aes.h"//for securing data
#include <cstring>  // For memset, memcpy
mbedtls_aes_context aes;
const char *userKey = "hyhT676#h~_1a"; //Security key. 


#include "LoRaWan_APP.h"
#include "AiEsp32RotaryEncoder.h"
#include "Arduino.h"
#define ROTARY_ENCODER_VCC_PIN -1

//instead of changing here, rather change numbers above
AiEsp32RotaryEncoder rotaryEncoder = AiEsp32RotaryEncoder(
            PIN_A, 
            PIN_B, 
            SW_PIN, 
            ROTARY_ENCODER_VCC_PIN, 
            ANGLE_STEP);



#define RF_FREQUENCY                                915432000 // Hz

#define TX_OUTPUT_POWER                             TX_POWER        // dBm from 2 to 20. when powered via battery 2 to 14dBm

#define LORA_BANDWIDTH                              0         // [0: 125 kHz,
                                                              //  1: 250 kHz,
                                                              //  2: 500 kHz,
                                                              //  3: Reserved]
#define LORA_SPREADING_FACTOR                       7         // [SF7..SF12]
#define LORA_CODINGRATE                             1         // [1: 4/5,
                                                              //  2: 4/6,
                                                              //  3: 4/7,
                                                              //  4: 4/8]
#define LORA_PREAMBLE_LENGTH                        8         // Same for Tx and Rx
#define LORA_SYMBOL_TIMEOUT                         0         // Symbols
#define LORA_FIX_LENGTH_PAYLOAD_ON                  false
#define LORA_IQ_INVERSION_ON                        false


#define RX_TIMEOUT_VALUE                            1000
#define BUFFER_SIZE                                 64 // Define the payload size here

char txpacket[BUFFER_SIZE];
char rxpacket[BUFFER_SIZE];

double txNumber;

bool lora_idle=true;

static RadioEvents_t RadioEvents;
unsigned long lastTxTime = 0;
void OnTxDone( void );
void OnTxTimeout( void );
void decryptAES(uint8_t *data, const char *key);
void encryptAES(uint8_t *data, const char *key);
void processKey(const char *userKey, uint8_t *processedKey, size_t keySize);
void VextON(void);

void rotary_loop();//prototyp function: rotary encoder
void IRAM_ATTR readEncoderISR();//prototyp function: rotary encoder
void rotary_onButtonClick();//prototyp function: rotary encoder

void setup() {
  Serial.begin(115200);
  Serial.println();

  VextON();
  delay(100);

	//we must initialize rotary encoder
	rotaryEncoder.begin();
	rotaryEncoder.setup(readEncoderISR);
	bool circleValues = false;
	rotaryEncoder.setBoundaries(0, MAX_ANGLE, circleValues); //minValue, maxValue, circleValues true|false (when max go to min and vice versa)
	/*Rotary acceleration introduced 25.2.2021.
   * in case range to select is huge, for example - select a value between 0 and 1000 and we want 785
   * without accelerateion you need long time to get to that number
   * Using acceleration, faster you turn, faster will the value raise.
   * For fine tuning slow down.
   */
	//rotaryEncoder.disableAcceleration(); //acceleration is now enabled by default - disable if you dont need it
	rotaryEncoder.setAcceleration(20); //or set the value - larger number = more accelearation; 0 or 1 means disabled acceleration
  rotaryEncoder.reset(homePosition); //set home position

  // Initialising the UI will init the display too.
  display.init();
  display.setFont(ArialMT_Plain_10);
  //LoRa stuff
  Mcu.begin(HELTEC_BOARD,SLOW_CLK_TPYE);
	
    txNumber=0;

    RadioEvents.TxDone = OnTxDone;
    RadioEvents.TxTimeout = OnTxTimeout;
    
    Radio.Init( &RadioEvents );
    Radio.SetChannel( RF_FREQUENCY );
    Radio.SetTxConfig( MODEM_LORA, TX_OUTPUT_POWER, 0, LORA_BANDWIDTH,
                                   LORA_SPREADING_FACTOR, LORA_CODINGRATE,
                                   LORA_PREAMBLE_LENGTH, LORA_FIX_LENGTH_PAYLOAD_ON,
                                   true, 0, 0, LORA_IQ_INVERSION_ON, 3000 );   

}


void displayAngle() {
    display.clear();  // Clear display before new content
    
    // Line 1: Text: Angle
    display.setTextAlignment(TEXT_ALIGN_LEFT);

    // Line 2: Temperature value in 24pt font
    display.setFont(ArialMT_Plain_24);
    
    // Format
    String angleString = String(servoAngel) + "°"; // 

    display.setFont(ArialMT_Plain_16);
    display.drawString(0, 0, labelAngle);        
    display.setFont(ArialMT_Plain_24);
    display.drawString(0, 15, angleString);  

    display.display();  // Update OLED
}



void VextON(void)
{
  pinMode(Vext,OUTPUT);
  digitalWrite(Vext, LOW);
}

void VextOFF(void) //Vext default OFF
{
  pinMode(Vext,OUTPUT);
  digitalWrite(Vext, HIGH);
}

void sendData()
{

  String txData = String(servoAngel) ; 

  uint8_t data[BUFFER_SIZE];       
  memset(data, 0, sizeof(data));  // Zero-padding
  strncpy((char*)data, txData.c_str(), sizeof(data) - 1); // Copy string safely

  encryptAES(data, userKey);  // Encrypt before sending  
  if(lora_idle == true)
    {
      //delay(1000);
      Radio.Send(data,  sizeof(data));
      if(debug){
      Serial.print("Sending: ");
      Serial.println((char *)data);
      }
      lora_idle = false;
      oldAngleValue =servoAngel;//keep record of angle change
    }
    Radio.IrqProcess( );  
}



void loop() {
  rotary_loop();
  // clear the display
  display.clear();

  displayAngle(); // 

  if(oldAngleValue != servoAngel)
  {
	  sendData();
  }
  //delay(100);

}


void OnTxDone( void )
{
        if(debug){
	        Serial.println("TX done......");
        }
	lora_idle = true;
}

void OnTxTimeout( void )
{
    Radio.Sleep( );
        if(debug){
	        Serial.println("TX Timeout......");
        }
    lora_idle = true;
}


/**
 * Converts a user-provided plaintext key into a fixed-length 16-byte (128-bit)
 * or 32-byte (256-bit) key.
 */
void processKey(const char *userKey, uint8_t *processedKey, size_t keySize) {
    memset(processedKey, 0, keySize); // Fill with zeros
    size_t len = strlen(userKey);
    if (len > keySize) len = keySize; // Truncate if too long
    memcpy(processedKey, userKey, len); // Copy valid key part
}

/**
 * Encrypts a 16-byte (one block) message using AES-128.
 */
void encryptAES(uint8_t *data, const char *key) {
    uint8_t processedKey[16]; // 128-bit key
    processKey(key, processedKey, 16);

    mbedtls_aes_init(&aes);
    mbedtls_aes_setkey_enc(&aes, processedKey, 128);
    mbedtls_aes_crypt_ecb(&aes, MBEDTLS_AES_ENCRYPT, data, data);
    mbedtls_aes_free(&aes);
}

/**
 * Decrypts a 16-byte (one block) message using AES-128.
 */
void decryptAES(uint8_t *data, const char *key) {
    uint8_t processedKey[16]; // 128-bit key
    processKey(key, processedKey, 16);

    mbedtls_aes_init(&aes);
    mbedtls_aes_setkey_dec(&aes, processedKey, 128);
    mbedtls_aes_crypt_ecb(&aes, MBEDTLS_AES_DECRYPT, data, data);
    mbedtls_aes_free(&aes);
}



void rotary_onButtonClick()
{
	static unsigned long lastTimePressed = 0;
	//ignore multiple press in that time milliseconds
	if (millis() - lastTimePressed < 500)
	{
		return;
	}
	lastTimePressed = millis();
  
	        if(debug){
	          Serial.print("button pressed ");
	          Serial.print(millis());
	          Serial.println(" milliseconds after restart");
          }
}

void rotary_loop()
{
	//dont print anything unless value changed
	if (rotaryEncoder.encoderChanged())
	{
		        if(debug){
	            Serial.print("Value: ");
		          Serial.println(rotaryEncoder.readEncoder());              
            }
    servoAngel = rotaryEncoder.readEncoder();

	}
	if (rotaryEncoder.isEncoderButtonClicked())
	{
    rotaryEncoder.reset(homePosition); 
    servoAngel = homePosition;
		rotary_onButtonClick();
	}
}

void IRAM_ATTR readEncoderISR()
{
	rotaryEncoder.readEncoder_ISR();
}