SIM800 and Nokia 5110 display

I have a couple of SIM800 modules and Nokia 5110 displays (PCD8544) lying around, so I decided to build a multi-functions device that utilize the features of SIM800 module beyond making calls and sending SMS. The aim of this project is show the capabilities of SIM800 (specially internet capabilities) in addition to have a simple UI featuring old Nokia phones style.

Main features:

• Request a text file from a URL and display the result on screen (support both Http and Https)
• Show network operator information (name, signal strength, network date & network time)
• Show your approximate location a.k.a LBS information (date, time, latitude, and longitude). Please note that the date and time are based on GMT time
• Save (to EEPROM) and retrieve last saved location information (date, time, latitude, and longitude)
• Upload your location info to a JSON server (jsonbin.io) including:
• - Google Maps link of your location
• - GMT date and time of the upload entry
• Scheduled location uploads (every 6 hours by default)
• Show weather info of your current location (using OpenWeatherMap API & LBS) including:
• - Weather condition
• - Current temperature + Min & Max temp (in Celsius)
• - Humidity level (in percentage)
• - Wind speed (in Meters per Second)
• Serial debugging a.k.a. Serial Passthrough
• Auto sleep when idle after a specific time period (30 seconds by default)
• Advanced sleep & wake up functions to minimize power consumption during sleep
• Simple menu to navigate (Nokia phones style)
• Optimized SRAM usage (more than 50% is available for local variables)
• Backlight control

#include <EEPROM.h>
#include <avr/sleep.h>
#include <avr/power.h>
#include <avr/wdt.h>
#include <Adafruit_GFX.h>
#include <Adafruit_PCD8544.h>

#define lcdBL 5         // LCD backlight pin
#define resetPin 6      // Reset pin of Sim800L
#define pwrPin A0       // controling an NPN transistor that provides 0V to GND pin of Sim800L
#define btnEnt 2
#define btnUp 3
#define btnDwn 7
#define MENU_ROW_HEIGHT 11
#define LCD_ROWS 5
#define RXLED 17
#define TXLED 30
#define COUNTER 2522   // auto upload sleep counter will make the device sleep for 6 hours (COUNTER * 1.07 * 8 seconds)

Adafruit_PCD8544 display = Adafruit_PCD8544(9, 8, 4);

unsigned long startMillis, currentMillis;
const unsigned long period PROGMEM = 30000; // The duration in milliseconds before the microcontroller goes to sleep
bool GPRSCon, isItSleep, exitBool;
byte menuPos, menuScreen, markerPos, menuStartAt;
const char* const menu[14] PROGMEM  = {"File Request", "Network Info", "Weather Info", "Location Info", "Save Location",
                                       "Last Saved" , "Upload Loc", "Auto Upload", "Connect", "Disconnect",
                                       "Light Switch", "Power Down", "Reset Sim800L", "Debug Mode"
                                      };
byte MENU_LENGTH =  sizeof(menu) / sizeof(menu[0]);

void setup() {
  pinMode(btnUp, INPUT_PULLUP);
  pinMode(btnDwn, INPUT_PULLUP);
  pinMode(btnEnt, INPUT_PULLUP);
  pinMode(lcdBL, OUTPUT);
  pinMode(resetPin, OUTPUT);
  pinMode(pwrPin, OUTPUT);
  pinMode(RXLED, OUTPUT);
  pinMode(TXLED, OUTPUT);
  digitalWrite(resetPin, HIGH);
  digitalWrite(RXLED, HIGH);
  digitalWrite(TXLED, HIGH);
  digitalWrite(resetPin, HIGH);
  digitalWrite(pwrPin, HIGH);
  digitalWrite(lcdBL, LOW);
  display.begin();
  display.setRotation(2);     // My screen is flipped upside down! :/
  display.clearDisplay();
  delay(4000);  // You may increase this if the duration isn't enough
  while (!checkSim800()) {
    display.clearDisplay();
    display.println(F("Sim800L is \nturned off or \nnot responding"));
    display.display();
    delay(2000);
    resetSim800();
  }
  waitToReg();
  showMenu();
  startMillis = millis();
}

void loop() {
  currentMillis = millis();
  if (isButtonDown(btnDwn) == true) {
    if (menuPos < MENU_LENGTH - 1) {
      menuPos++;
      if (menuPos - menuStartAt > 3 )
        menuStartAt++;
      showMenu();
    }
    delay(100);
    startMillis = currentMillis;
  }
  if (isButtonDown(btnUp) == true) {
    if (menuPos > 0) {
      menuPos--;
      if (menuPos - menuStartAt < 0 && menuStartAt != 0)
        menuStartAt--;
      showMenu();
    }
    delay(100);
    startMillis = currentMillis;
  }
  if (isButtonDown(btnEnt) == true) {
    if (menuPos == 0) {
      const String s = openURL(F("raw.githubusercontent.com/HA4ever37/Sim800l/master/Sim800.txt"), true); // Change the URL to your text file link
      if (s == "ERROR" || s == "")  {
        display.clearDisplay();
        display.println(F("Bad request! \ntry again"));
        display.display();
        delay(2000);
      }
      else {
        s = s.substring(s.indexOf(F("\r")) + 2, s.lastIndexOf(F("OK")));
        s = s.substring(s.indexOf(F("\r")) + 2, s.length() - 1);
        display.clearDisplay();
        digitalWrite(lcdBL, LOW);
        /*for (byte i = 0; i < s.length(); i++) {
          //Serial.print(s.charAt(i));
          display.print(s.charAt(i));
          }*/
        display.print(s);
        display.display();
        digitalWrite(lcdBL, HIGH);
        delay(500);
        digitalWrite(lcdBL, LOW);
        while (!isButtonDown(btnEnt) && !isButtonDown(btnUp) && !isButtonDown(btnDwn));
      }
      showMenu();
    }
    else if (menuPos == 1) {
      netInfo();
      showMenu();
    }
    else if (menuPos == 2) {
      const String s = openURL(locInfo(3), false);
      char split = '"';
      int pos = s.indexOf(F("description\":\"")) + 14;
      String weather = s.substring(pos, s.indexOf(split, pos));
      weather[0] = toupper(weather[0]);
      display.clearDisplay();
      display.println(weather);
      split = ',';
      pos = s.indexOf(F("temp\":")) + 6;
      display.print(F("Temp:"));
      display.print(s.substring(pos, s.indexOf(split, pos)));
      display.println(F(" C"));
      pos = s.indexOf(F("p_min\":")) + 7;
      display.print(F("Min:"));
      display.print(s.substring(pos, s.indexOf(split, pos)));
      display.println(F(" C"));
      split = '}';
      pos = s.indexOf(F("p_max\":")) + 7;
      display.print(F("Max:"));
      display.print(s.substring(pos, s.indexOf(split, pos)));
      display.println(F(" C"));
      split = ',';
      pos = s.indexOf(F("humidity\":")) + 10;
      display.print(F("Humidity:"));
      display.print(s.substring(pos, s.indexOf(split, pos)));
      display.println(F("%"));
      pos = s.indexOf(F("speed\":")) + 7;
      display.print(F("Wind:"));
      display.print(s.substring(pos, s.indexOf(split, pos)));
      //display.print(s.substring(s.indexOf(F("speed\":")) + 7, s.indexOf(F(",\"deg"))));
      display.print(F(" m/s"));
      display.display();
      while (!isButtonDown(btnEnt) && !isButtonDown(btnUp) && !isButtonDown(btnDwn));
      showMenu();
    }
    else if (menuPos == 3) {
      locInfo(0);
      showMenu();
    }
    else if (menuPos == 4) {
      locInfo(2);
      showMenu();
    }
    else if (menuPos == 5) {
      readEeprom();
      showMenu();
    }
    else if (menuPos == 6) {
      locInfo(1);
      showMenu();
    }
    else if (menuPos == 7)
      autoUp();
    else if (menuPos == 8) {
      connectGPRS();
      showMenu();
    }
    else if (menuPos == 9) {
      disConnectGPRS();
      showMenu();
    }
    else if (menuPos == 10)
      toggle();
    else if (menuPos == 11)
      pwrDown();
    else if (menuPos == 12) {
      resetSim800();
      showMenu();
    }
    else if (menuPos == 13) {
      debugMode();
      showMenu();
    }
    delay(100);
    startMillis = currentMillis = millis();
  }
  if (currentMillis - startMillis >= period)
    pwrDown();
}

void waitToReg() {
  display.clearDisplay();
  display.println(F("Waiting to \nregister sim \ncard"));
  display.display();
  do {
    Serial1.print(F("AT+COPS?\r"));
  } while (Serial1.readString().indexOf(F("+COPS: 0,0,\"")) == -1);
}

String openURL(String string, bool ssl) {
  while (!GPRSCon)
    connectGPRS();
  display.clearDisplay();
  Serial1.print(F("AT+HTTPINIT\r"));
  display.println(F("HTTP \nIntialization\n"));
  display.display();
  if (Serial1.readString().indexOf(F("OK")) == -1)
    return;
  Serial1.print(F("AT+HTTPPARA=\"CID\",1\r"));
  Serial1.readString();
  display.print(F("Sending URL\nrequest"));
  display.display();
  Serial1.print(F("AT+HTTPPARA=\"URL\",\""));
  Serial1.print(string + "\"\r");
  if (Serial1.readString().indexOf(F("OK")) == -1)
    return;
  display.print(Serial1.readString());
  display.display();
  display.clearDisplay();
  Serial1.print(F("AT+HTTPPARA=\"REDIR\",1\r"));
  Serial1.readString();
  if (ssl) {
    Serial1.print(F("AT+HTTPSSL=1\r"));
    Serial1.readString();
  }
  else {
    Serial1.print(F("AT+HTTPSSL=0\r"));
    Serial1.readString();
  }
  Serial1.print(F("AT+HTTPACTION=0\r"));
  Serial1.readString();
  while (!Serial1.available());
  Serial1.readString();
  if (Serial1.readString().indexOf(F(",200,")) != -1)
    return;
  display.print(F("Downloading \ndata"));
  display.display();
  Serial1.print(F("AT+HTTPREAD\r"));
  string = Serial1.readString();
  string.trim();
  Serial1.print(F("AT+HTTPTERM\r"));
  Serial1.readString();
  return string;
}

String locInfo(byte save) {
  while (!GPRSCon)
    connectGPRS();
  display.clearDisplay();
  display.println(F("Getting\nlocation info\n"));
  display.display();
  Serial1.print(F("AT+CIPGSMLOC=1,1\r"));
  Serial1.readString();
  while (!Serial1.available());
  String s = Serial1.readString();
  if (s.indexOf(F(",")) == -1) {
    display.println(F("Failed to \nget info!"));
    display.display();
    delay(2000);
  }
  else {
    s = s.substring(s.indexOf(F(",")) + 1, s.indexOf(F("OK")));
    s.trim();
    const String data[4];
    for (byte i = 0; i < 4; i++) {
      data[i] = s.substring(0, s.indexOf(F(",")));
      s = s.substring(s.indexOf(F(",")) + 1, s.length());
    }
    if (save == 0) {
      display.clearDisplay();
      display.print(F("Dt:"));
      display.println(data[2]);
      display.print(F("Time:"));
      display.println(data[3]);
      display.println(F("Latitude: "));
      display.println(data[1]);
      display.println(F("Longitude: "));
      display.println(data[0]);
      display.display();
      while (!isButtonDown(btnEnt) && !isButtonDown(btnUp) && !isButtonDown(btnDwn));
    }
    else if (save == 1) {
      display.print(F("Connecing to\nupload server"));
      display.display();
      display.clearDisplay();
      s = "{\"Date\": \"" + data[2] + "\", \"Time\": \"" + data[3] + "\", \"Location link\": \"www.google.com/maps?q=" + data[1] + "," + data[0] + "\"}";
      Serial1.print(F("AT+HTTPINIT\r"));
      Serial1.readString();
      Serial1.print(F("AT+HTTPPARA=\"CID\",1\r"));
      Serial1.readString();
      Serial1.print(F("AT+HTTPSSL=0 \r"));
      Serial1.readString();
      Serial1.print(F("AT+HTTPPARA=\"URL\",\"api.jsonbin.io/b\"\r"));
      Serial1.readString();
      Serial1.print(F("AT+HTTPPARA=\"CONTENT\",\"application/json\"\r"));
      Serial1.readString();
      // WARNING!!!  YOU MUST CHANGE the secret-key otherwise your location info will be sent to my JSON account!
      Serial1.print(F("AT+HTTPPARA=\"USERDATA\",\"secret-key: $2a$10$/4cwS1j8JzAgdbYKEDbeM.x19a0UM5C612PtEvoBv.hqtGagcY.DG\\r\\nprivate: true\"\r"));
      Serial1.readString();
      Serial1.print(F("AT+HTTPDATA="));
      Serial1.print(String(s.length()) + ",2000\r");
      Serial1.readString();
      Serial1.print(s + "\r");
      Serial1.readString();
      Serial1.print(F("AT+HTTPACTION=1\r"));
      Serial1.readString();
      while (!Serial1.available());
      s = Serial1.readString();
      if (s.indexOf(F(",200,")) == -1 ) {
        display.print(F("Failed to\nupload info!"));
        display.display();
      }
      else {
        display.println(F("Location \nuploaded!"));
        display.display();
      }
      Serial1.print(F("AT+HTTPREAD\r"));
      Serial1.readString();
      Serial1.print(F("AT+HTTPTERM\r"));
      Serial1.readString();
    }
    else if (save == 2) {
      writeEeprom("Dt:" + data[2] + "\nTime:" + data[3] + "\nLongitude:\n" + data[0] + "\nLatitude:\n" + data[1]);
      display.println(F("Info saved \nto Eeprom!:"));
      display.display();
      delay(2000);
    }
    else if (save == 3) {
      s = F("api.openweathermap.org/data/2.5/weather?lon=");
      s += data[0];
      s += F("&lat=");
      s += data[1];
      s += F("&units=metric&appid=0a3456488cb52d167293ee9ca1f00539"); // Please change the App id to your API key
      return s;
    }
  }
  s = "";
  return s;
}

void netInfo() {
  if (isItSleep) {
    wakeUp();
    isItSleep = false;
  }
  display.clearDisplay();
  display.println(F("Getting\nnetwork info"));
  display.display();
  const String data[2];
  String network;
  do {
    Serial1.print(F("AT+COPS?\r"));
    network = Serial1.readString();
    //Serial.println(network);
  } while (network.indexOf(F("+COPS: 0,0,\"")) == -1);
  network = network.substring(network.lastIndexOf(F(",\"")) + 2, network.lastIndexOf(F("\"")));
  exitBool = false;
  attachInterrupt(digitalPinToInterrupt(btnEnt), exitLoop, FALLING);
  while (!exitBool) {
    Serial1.print(F("AT+CSQ\r"));
    String quality = Serial1.readString();
    quality = quality.substring(quality.indexOf(F(": ")) + 2, quality.indexOf(F(",")));
    if (quality.toInt() < 10)
      quality = "Poor " + quality;
    else if (quality.toInt() < 15)
      quality = "Fair " + quality;
    else if (quality.toInt() < 20)
      quality = "Good " + quality;
    else
      quality = "Excellent " + quality;
    Serial1.print(F("AT+CCLK?\r"));
    const String s = Serial1.readString();
    char am_pm[] = "AM";
    byte hrs = 12;
    data[0] = s.substring(s.indexOf(F("\"")) + 1, s.indexOf(F(",")));
    data[1] = s.substring(s.indexOf(F(",")) + 1, s.indexOf(F("-")));
    if (data[1].substring(0, 2).toInt() > hrs) {
      am_pm[0] = 'P';
      hrs = data[1].substring(0, 2).toInt() - hrs;
    }
    else if (data[1].substring(0, 2).toInt() == hrs)
      am_pm[0] = 'P';
    else if (data[1].substring(0, 2).toInt() == 0);
    else if (data[1].substring(0, 2).toInt() < hrs)
      hrs = data[1].substring(0, 2).toInt();
    display.clearDisplay();
    display.println(network);
    display.println(F("Sig. Strength:"));
    display.println(quality);
    display.println(F("Date & Time:"));
    display.print(F("20"));
    display.println(data[0]);
    display.println(String(hrs) + data[1].substring(2, data[1].length() ) + " " + am_pm);
    display.display();
  }
}

void exitLoop() {
  if (isButtonDown(btnEnt)) {
    detachInterrupt(btnEnt);
    exitBool = true;
  }
}

bool checkGPRS() {
  Serial1.print(F("AT+SAPBR=2,1\r"));
  if (Serial1.readString().indexOf(F("+SAPBR: 1,1,")) != -1)
    return true;
  return false;
}

void connectGPRS() {
  if (isItSleep) {
    wakeUp();
    isItSleep = false;
  }
  if (checkGPRS()) {
    display.clearDisplay();
    display.println(F("Already \nconnected!"));
    display.display();
    delay(2000);
  }
  else {
    display.clearDisplay();
    display.println(F("Initializing \nSim800L\n"));
    display.display();
    Serial1.print(F("AT+CSCLK=0\r"));
    while (!Serial1.available());
    Serial1.readString();
    Serial1.print(F("AT+SAPBR=3,1,\"APN\",\"pwg\"\r"));   // Need to be changed to your APN
    Serial1.readString();
    display.println(F("Trying to\nconnect to the\naccess point"));
    display.display();
    display.clearDisplay();
    Serial1.print(F("ATE0\r"));
    Serial1.readString();
    Serial1.print(F("AT+SAPBR=1,1\r"));
    while (!Serial1.available());
    if (Serial1.readString().indexOf(F("OK")) != -1) {
      display.print(F("Connected!"));
      GPRSCon = true;
    }
    else {
      display.print(F("Failed to \nconnect!"));
      display.display();
      delay(1000);
      resetSim800();
      waitToReg();
    }
    Serial1.print(F("ATE1\r"));
    Serial1.readString();
  }
}

void disConnectGPRS() {
  if (!checkGPRS()) {
    display.clearDisplay();
    display.println(F("Already \ndisconnected!"));
    display.display();
    delay(2000);
  }
  else {
    display.clearDisplay();
    display.print(F("Disconnecting \nGPRS"));
    display.display();
    Serial1.print(F("AT+SAPBR=0,1\r"));
    Serial1.readString();
    delay(100);
    Serial1.print(F("AT+CSCLK=2\r"));
    Serial1.readString();
    GPRSCon = false;
  }
}

void readEeprom() {
  String s;
  for (int i = 0; EEPROM.read(i) != 0 && i < EEPROM.length(); i++)
    s += (char)EEPROM.read(i);
  display.clearDisplay();
  display.print(s);
  display.display();
  delay(100);
  while (!isButtonDown(btnEnt) && !isButtonDown(btnUp) && !isButtonDown(btnDwn));
}

void writeEeprom(String s) {
  for (int i = 0; i < s.length() && i < EEPROM.length(); i++) {
    EEPROM.update(i, s.charAt(i));
  }
}

void resetSim800() {
  if (isItSleep) {
    wakeUp();
    isItSleep = false;
  }
  else {
    display.clearDisplay();
    display.println(F("Restarting"));
    display.display();
    digitalWrite(resetPin, LOW);
    delay(100);
    digitalWrite(resetPin, HIGH);
    GPRSCon = false;
    delay(2000);
    waitToReg();
  }
}

void autoUp() {
  display.clearDisplay();
  display.println(F("To disable \nautoupload\nplease restart\nthe device"));
  display.display();
  delay(3000);
  while (true) {
    if (isItSleep)
      connectGPRS();
    locInfo(1);
    Serial1.print(F("AT+CPOWD=0\r"));
    Serial1.readString();
    digitalWrite(lcdBL, HIGH);  // keep the LCD backlight off during sleep time and wakeups to reduce power consumption
    display.clearDisplay();
    display.display();
    display.command( PCD8544_FUNCTIONSET | PCD8544_POWERDOWN);
    digitalWrite(pwrPin, LOW);
    for (int i = 0; i < COUNTER; i++)
      myWatchdogEnable (0b100001);  // 8 seconds
    //myWatchdogEnable (0b100000);  // 4
    sleep_disable();
    power_all_enable();
    display.begin();
    isItSleep = true;
  }
}

void toggle() {
  if (isButtonDown(btnEnt))
    digitalWrite(lcdBL, !digitalRead(lcdBL));
}

bool isButtonDown(byte pin) {
  if (digitalRead(pin) == LOW) {
    delay(30);
    if (digitalRead(pin) == LOW)
      return true;
    return false;
  }
  return false;
}

void showMenu() {
  for (byte i = menuStartAt; i < (menuStartAt + LCD_ROWS); i++) {
    byte markerY = (i - menuStartAt) * MENU_ROW_HEIGHT;
    if (i == menuPos) {
      display.setTextColor(WHITE, BLACK);
      display.fillRect(0, markerY, display.width(), MENU_ROW_HEIGHT, BLACK);
    }
    else {
      display.setTextColor(BLACK, WHITE);
      display.fillRect(0, markerY, display.width(), MENU_ROW_HEIGHT, WHITE);
    }
    if (i >= MENU_LENGTH)
      continue;
    display.setCursor(3, markerY + 2);
    display.print((char*)pgm_read_word(&(menu[i])));
  }
  display.display();
}

bool checkSim800() {
  Serial1.begin(9600);
  while (Serial1.available() > 0)
    Serial1.read();
  Serial1.print(F("AT\r"));
  delay(100);
  if (Serial1.available() > 0) {
    Serial1.read();
    return true;
  }
  else
    return false;
}

void wakeUp() {
  digitalWrite(resetPin, HIGH);
  digitalWrite(pwrPin, HIGH);
  display.clearDisplay();
  display.println(F("Waking up \nSim800L"));
  display.display();
  delay(4000);
  while (!checkSim800()) {
    display.clearDisplay();
    display.println(F("Sim800L is \nturned off or \nnot responding"));
    display.display();
    delay(2000);
    resetSim800();
  }
  waitToReg();
}

void pwrDown() {
  delay(250);   //debouncing
  isItSleep = true;
  GPRSCon = false;
  digitalWrite(lcdBL, HIGH);
  display.clearDisplay();
  display.display();
  display.command( PCD8544_FUNCTIONSET | PCD8544_POWERDOWN);
  digitalWrite(pwrPin, LOW);
  attachInterrupt(digitalPinToInterrupt(btnEnt), pinInterrupt, RISING);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_enable();
  savePower();
  sleep_mode();
  sleep_disable();
  power_all_enable();
  MENU_LENGTH =  13;
  display.begin();
  digitalWrite(lcdBL, LOW);
  startMillis = currentMillis = millis();
  showMenu();
}

void debugMode() {
  Serial.begin(9600);
  display.clearDisplay();
  display.println(F("Press enter to\nexit debug \nmode"));
  display.display();
  exitBool = false;
  delay(250);   //debouncing
  attachInterrupt(digitalPinToInterrupt(btnEnt), exitLoop, FALLING);
  while (!exitBool) {
    if (Serial.available()) {
      Serial1.write(Serial.read());
    }
    if (Serial1.available()) {
      Serial.write(Serial1.read());
    }
  }
}

void pinInterrupt(void) {
  detachInterrupt(btnEnt);
}

void ledTx( boolean on) {
  if (on)  {
    pinMode( LED_BUILTIN_TX, OUTPUT);    // pin as output.
    digitalWrite( LED_BUILTIN_TX, LOW);  // pin low
  }
  else {
    pinMode( LED_BUILTIN_TX, INPUT);
  }
}

void ledRx( boolean on) {
  if (on) {
    pinMode( LED_BUILTIN_RX, OUTPUT);
    digitalWrite( LED_BUILTIN_RX, LOW);
  }
  else {
    pinMode( LED_BUILTIN_RX, INPUT);
  }
}

ISR(WDT_vect) {
  wdt_disable();
}

void myWatchdogEnable(const byte interval) {
  MCUSR = 0;                          // reset various flags
  WDTCSR |= 0b00011000;               // see docs, set WDCE, WDE
  WDTCSR =  0b01000000 | interval;    // set WDIE, and appropriate delay
  set_sleep_mode (SLEEP_MODE_PWR_DOWN);
  wdt_reset();
  savePower();
  sleep_mode();            // now goes to Sleep and waits for the interrupt
}

void savePower() {
  ADCSRA = 0;
  power_adc_disable();
  ACSR |= (1 << ACD); // disable Analog comparator, saves 4 uA
  DIDR0 = 0x3F; //Disable digital input buffers on all ADC0-ADC5 pins
  DIDR1 = (1 << AIN1D) | (1 << AIN0D);
  power_usart0_disable();
  power_usart1_disable();
  power_spi_disable();
  power_twi_disable();
  power_timer0_disable();  // Do not disable if you need millis()!!!
  power_timer1_disable();
  power_timer3_disable();
  PRR1 |= (uint8_t)(1 << 4);  //PRTIM4
  power_usart1_disable();
  // Disable the USB interface
  USBCON &= ~(1 << USBE);
  // Disable the VBUS transition enable bit
  USBCON &= ~(1 << VBUSTE);
  // Disable the VUSB pad
  USBCON &= ~(1 << OTGPADE);
  // Freeze the USB clock
  USBCON &= ~(1 << FRZCLK);
  // Disable USB pad regulator
  UHWCON &= ~(1 << UVREGE);
  // Clear the IVBUS Transition Interrupt flag
  USBINT &= ~(1 << VBUSTI);
  // Physically detact USB (by disconnecting internal pull-ups on D+ and D-)
  UDCON |= (1 << DETACH);
  power_usb_disable();  // Keep it here, after the USB power down
  // Disable functions
  power_all_disable();
}