Old-School Two-Way Pager with Arduino

/**
 * Two-way pager system with Arduino and Hologram cellular service
 * Mike Schaus
 * Dec 28, 2016
 * Made as part of the Hologram Hacker-In-Residence program
 * 
 * This project sends and receives text (SMS) messages via 
 * an arduino with cellular modem built into a small enclosure 
 * with an LCD display and simple control buttons.
 * 
 * Note that code is included to function via the LCD shield OR
 * the serial monitor, so you can use this code even without
 * an LCD shield.
 */

#include <GSM.h>

#define PINNUMBER ""

// include the LCD library code:
#include <Wire.h>
#include <Adafruit_RGBLCDShield.h>
#include <utility/Adafruit_MCP23017.h>

// The shield uses the I2C SCL and SDA pins. On classic Arduinos
// this is Analog 4 and 5 so you can't use those for analogRead() anymore
// However, you can connect other I2C sensors to the I2C bus and share
// the I2C bus.
Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();

// These #defines make it easy to set the backlight color
#define OFF 0x0
#define ON 0x1

// make the arrow special character on the LCD
const byte arrow[8] =
{
 B00000, B00000, B01000, B01100, B01110, B01100, B01000, B00000
};

// initialize the GSM library instance
GSM gsmAccess(false); // include a 'true' parameter for debug enabled
GSM_SMS sms;

// char array of the telephone number to send SMS
// change the number 12125551212 to a number
// you have access to
char remoteNumber[20]= "12125551212";

// Array to hold the number a SMS is retreived from
char senderNumber[20];

// char array of the possible outgoing messages to choose from the menu
char* responses[]={"Mike=Awesome!", "Yes", "No", "Howdy!"};
//#define NUMRESPONSES 4 // if someone knows how to calculate this instead, I'm all ears
#define NUMRESPONSES (sizeof(responses)/sizeof(char *)) // thanks to Steve Kemp's comment!

int position=-1; // this way the first button press will always show first option of the menu

int inByte = 0; // incoming serial byte for keyboard interface

boolean backlight = true; // track backlight status for toggling

unsigned long previousMillis = 0; // will store last time messages were checked
#define CHECKINTERVAL 1500 // how often to check for text messages

void setup() {
  // put your setup code here, to run once:

  // initialize serial communications
  Serial.begin(9600);
  Serial.println(F("SMS Message Sender -- starting up..."));

  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);

  // Print a message to the LCD
  lcd.print(F("Hello, Hologram!"));
  lcd.setCursor(0, 1);
  lcd.print(F("Starting up..."));
  lcd.setBacklight(ON);

  // set up the arrow character for display
  lcd.createChar(0, arrow);

  // connection state
  boolean notConnected = true;

  // Start GSM shield
  // If your SIM has PIN, pass it as a parameter of begin() in quotes
  while(notConnected)
  {
    if(gsmAccess.begin(PINNUMBER)==GSM_READY) {
      notConnected = false;
      Serial.println(F("GSM is connected because you are so awesome"));
      Serial.println(F("Waiting for messages, or send with \"s\""));
      Serial.println();

      lcd.clear();
      lcd.setCursor(0,0);
      homeScreen();

    }
    else
    {
      Serial.println(F("Not connected"));
      lcd.clear();
      lcd.setCursor(0,0);
      lcd.print(F("Not connected"));
      delay(1000);
    }
  }
}

// this is the menu system function
void showResponses() {
//  Serial.println(position); // only for debugging menu system

  lcd.clear();
  lcd.setCursor(0,0);
  
  // make sure cursor position is legal
  if (position<0) position=0;
  if (position>NUMRESPONSES-1) position = NUMRESPONSES-1;

  // write current selection and next option if there is another option
  lcd.write(0); //arrow character
  lcd.print(position+1);
  lcd.print("-");
  lcd.print(responses[position]);
  if (position < NUMRESPONSES-1) {
    lcd.setCursor(0,1);
    lcd.print(" ");
    lcd.print(position+2);
    lcd.print("-");
    lcd.print(responses[position+1]);
  }
}


void homeScreen() {
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("SMS Messenger!");
  lcd.setCursor(0,1);
  lcd.print("Ready; up/dn snd");

  position=-1; //reset response selection
}


void receiveSMS(){
  
  char c;

  // If there are any SMSs available()
  if (sms.available()) {
    Serial.println("Message received from:");

    // Get remote number
    sms.remoteNumber(senderNumber, 20);
    Serial.println(senderNumber);

    lcd.clear();
    lcd.setCursor(0,0);
    backlight = true;
    lcd.setBacklight(ON);

    // An example of message disposal
    // Any messages starting with # should be discarded
    if (sms.peek() == '#') {
      Serial.println("Discarded SMS");
      sms.flush();
    }

    // Read message bytes and print them
    // because sms.read only returns one character at a time
    int i=0;
    while (c = sms.read()) {
      i++;
      Serial.print(c);
      if (i==17) lcd.setCursor(0, 1); // move to next line if needed
      if (i<33) lcd.print(c); // don't try to print more than 32 chars just in case
    }

    Serial.println("\nEND OF MESSAGE");

    // Delete message from modem memory
    sms.flush();
    Serial.println("MESSAGE DELETED");
    Serial.println();

    // wait for right button to acknowlege before letting program continue
    boolean acknowledged = false;
    while(!acknowledged) {
      uint8_t buttons = lcd.readButtons();
      if (buttons & BUTTON_RIGHT) acknowledged = true;
      delay(50); //short delay for troubleshooting -- without this it behaves strangely
    }
    homeScreen();
    delay(400); // prevent multiple presses in a row
  }
}

// function to show message options in the serial monitor
void printResponseOptions(){
  for(int i=0; i<NUMRESPONSES; i++){
    Serial.print(i);
    Serial.print("-");
    Serial.println(responses[i]);
  }
  Serial.println();
}


void sendSMS(const char* txtMsg){

  Serial.print("Message to mobile number: ");
  Serial.println(remoteNumber);

  // print sms text info
  Serial.println("SENDING");
  Serial.println("Message:");
  Serial.println(txtMsg);

  // send the message
  sms.beginSMS(remoteNumber);
  sms.print(txtMsg);
  // next, add a signature to the chosen message
  sms.print(" --Be sure to connect with me on my blog http://mschausprojects.blogspot.com");
  // call endSMS function to finish sending; it will return 1 if successful
  if (sms.endSMS()==1) {
    Serial.println("\nCOMPLETE!\n");
    homeScreen();
  }
  else {
    Serial.println("\nERROR\n");
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print("error");
  }
  Serial.println();
}



void loop() {
  // put your main code here, to run repeatedly:

  uint8_t buttons = lcd.readButtons();

  if (buttons) {
    if (buttons & BUTTON_UP) {
      position--;
      showResponses();
      backlight = true;
      lcd.setBacklight(ON);
    }
    if (buttons & BUTTON_DOWN) {
      position++;
      showResponses();
      backlight = true;
      lcd.setBacklight(ON);
    }
    if (buttons & BUTTON_LEFT) {
      homeScreen();
      backlight = true;
      lcd.setBacklight(ON);
    }
    if (buttons & BUTTON_RIGHT) {
      backlight = !backlight; // toggle the backlight state
      if (backlight) lcd.setBacklight(ON);
      else lcd.setBacklight(OFF);
      homeScreen(); // have to write to screen after turning light off, otherwise it goes blank
    }
    if (buttons & BUTTON_SELECT) {
      // make sure cursor selected position is legal
      if (position<0) position=0;
      
      lcd.clear();
      lcd.setCursor(0,0);
      lcd.print("Sending...");
      lcd.setCursor(0,1);
      lcd.print(responses[position]);
      backlight = true;
      lcd.setBacklight(ON);
      sendSMS(responses[position]);
    }
    delay(200); // prevent multiple presses in a row
  }


  // this is for serial interface only, not related to LCD and buttons
  // send a message when I type "s" in serial monitor
  // then wait for my selection of the response number
  if (Serial.available() > 0) {
    inByte = Serial.read(); // get incoming byte
    if (inByte == 's') {
      printResponseOptions();

      while (Serial.available() > 0) {  // clear the keyboard buffer just in case
        char junk = Serial.read();
      }
  
      while (Serial.available() == 0) ;  // Wait here until input buffer has a character
      inByte = Serial.parseInt();
      // would want to check for valid choice here to be more robust
      sendSMS(responses[inByte]);
    }
  }

  // check for new messages only once every few seconds to keep interface more responsive
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= CHECKINTERVAL) {
    previousMillis = currentMillis;
    receiveSMS(); // takes about 26ms when there are no messages
  }
}