// This software, known as CarbOnBal is
// Copyright, 2017-2020 L.L.M. (Dennis) Meulensteen. [email protected]
//
// This file is part of CarbOnBal. A combination of software and hardware.
// I hope it may be of some help to you in balancing your carburetors and throttle bodies.
// Always be careful when working on a vehicle or electronic project like this.
// Your life and health are your sole responsibility, use wisely.
//
// CarbOnBal hardware is covered by the CERN Open Hardware License v1.2
// a copy of the text is included with the source code.
//
// CarbOnBal is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// CarbOnBal is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with CarbOnBal.  If not, see <http://www.gnu.org/licenses/>.

//#define DEBUG
#include "Arduino.h"
#include "EEPROM.h"

#include "functions.h"
#include "globals.h"
#include LANGUAGE
#include "lang_generic.h"
#include "lcdWrapper.h"
#include "menu.h"
#include "menuActions.h"
#include "utils.h"
settings_t settings;
uint8_t settingsOffset = 2;

// The software uses a lot of global variables. This may not be elegant but its one way of writing non-blocking code

int refresh_r = 100;
int inputPin[NUM_SENSORS] = { A1, A2 }; //used as a means to access the sensor pins using a counter
int timeBase = 0; //allows us to calculate how long it took to measure and update the display (only used for testing)
unsigned long lastPeak[NUM_SENSORS];
unsigned long lastMin[NUM_SENSORS];
bool freezeDisplay = false; //used to tell when a user wants to freeze the display
unsigned int rpm;                                       //stores the current RPM
int crete = 550;
unsigned int average[NUM_SENSORS]; //used to share the current average for each sensor
unsigned int min_val[NUM_SENSORS] = {1024,1024}; //used to share the current average for each sensor
unsigned int min_val_raw[NUM_SENSORS] = {1024,1024}; //used to share the current average for each sensor
unsigned int max_val_raw[NUM_SENSORS] = {0,0}; //used to share the current average for each sensor
int ambientPressure; //stores current ambient pressure for negative pressure display
unsigned long lastUpdate;
int emaTarget = -1;
unsigned long emaMillis = 0;
longAverages avg[NUM_SENSORS];

uint8_t labelPosition = 0;

unsigned long startTime;

//this does the initial setup on startup.
void setup() {
  lcd_begin(DISPLAY_COLS, DISPLAY_ROWS);
  pinMode(LED_BUILTIN, OUTPUT);

  settings = loadSettings(settings); //load saved settings into memory from FLASH

#ifdef DEBUG
  Serial.begin(BAUD_RATE);
#endif
  setInputActiveLow(SELECT);          //set the pins connected to the switches
  setInputActiveLow(LEFT);             //switches are wired directly and could
  setInputActiveLow(RIGHT);                //short out the pins if setup wrong
  setInputActiveLow(CANCEL);

  analogWrite(brightnessPin, settings.brightness);  //brightness is PWM driven
  analogWrite(contrastPin, settings.contrast); //contrast is PWM with smoothing (R/C network) to prevent flicker

  ambientPressure = detectAmbient(); //set ambient pressure (important because it varies with weather and altitude)

  //set timer1 interrupt at 1Hz
  TCCR1A = 0; // set entire TCCR1A register to 0
  TCCR1B = 0; // same for TCCR1B
  TCNT1 = 0; //initialize counter value to 0
  // set compare match register for 1hz increments
  OCR1A = 249;  // = (16*10^6) / (1*1024) - 1 (must be <65536)
  // turn on CTC mode
  TCCR1B |= (1 << WGM12);
  // Set CS10 and CS11 bits for 64 prescaler
  TCCR1B |= (1 << CS11) | (1 << CS10);
  // enable timer compare interrupt
  TIMSK1 |= (1 << OCIE1A);
  setInterrupt(true);

}

void loop() {
  startTime = micros();

//  if (emaTarget >= 0) {
//    if ((millis() - emaMillis) >= 125) {
//      if (emaTarget > settings.damping) {
//        settings.damping++;
//      } else {
//        emaTarget = -1;
//      }
//      emaMillis = millis();
//    }
//  }

  switch (buttonPressed()) {          //test if a button was pressed
  case SELECT:
    actionDisplayMainMenu();
    break;        //the menu is the only function that does not return asap

  case LEFT:
    settings.damping = (int8_t) (doBasicSettingChanger(txtDampingPerc,0, 100, (int8_t) settings.damping * 6.25, 6) / 6.25);
      actionSaveSettings();
      lcd_clear();
    break;

  case RIGHT:
      settings.rpmDamping = (int8_t) (doBasicSettingChanger(txtRpmDampingPerc, 0, 100,(int8_t) settings.rpmDamping * 6.25, 6) / 6.25);
      actionSaveSettings();
      lcd_clear();
    break;

  case CANCEL:
    lcd_clear();
    do_raw_data();
//     freezeDisplay = !freezeDisplay; //toggle the freezeDisplay option
//      freezeDisplay = false;
//      doRevs();
      break;
  }
  

  if (!freezeDisplay
      && (settings.graphType == 2 || (millis() - lastUpdate) > refresh_r)) {//only update the display every 100ms or so to prevent flickering
  
    switch (settings.graphType) { //there are two types of graph. bar and centered around the value of the master carb
    case 0:
      lcdBarsSmooth(average,0);
      lastUpdate = millis();
      break;          //these functions both draw a graph and return asap
    case 1:
      lcdBarsCenterSmooth(average);
      lastUpdate = millis();
      break;    //
    } 
    printLcdInteger(rpm, 5, 3, 6);
    lcd_setCursor(11, 3);
    lcd_print(F("rpm"));

  } else if (freezeDisplay) {
    //show a little snow flake to indicate the frozen state of the display
    drawSnowFlake();
  }

  timeBase = micros() - startTime; //monitor how long it takes to traverse the main loop
  #ifdef DEBUG
//    Serial.print(timeBase);
//    Serial.print("  ");
  #endif

}

void intRunningAverage(){
  int factor = settings.damping;
  int rpm_factor = settings.rpmDamping;
  int delta[NUM_SENSORS] = {0,0};
  unsigned int value[NUM_SENSORS];
  longAverages rpmAverage;

  for (int sensor = 0; sensor < 2; sensor++) { //loop over all sensors
    value[sensor] = readSensorRaw(sensor);
    if (value[sensor] < min_val[sensor]){
      min_val[sensor] = value[sensor];
      lastMin[sensor] = millis();
    }
    delta[sensor] = millis() - lastPeak[sensor];
    if (value[sensor] > crete && millis() > lastMin[sensor] && delta > 20 ){
      avg[sensor].longVal = longExponentialMovingAverage(factor, avg[sensor].longVal, min_val[sensor]);
      average[sensor] = avg[sensor].intVal[1];

      if (sensor == settings.master-1){
        rpmAverage.longVal = longExponentialMovingAverage(rpm_factor,
          rpmAverage.longVal, 120000/delta[sensor]);
        rpm = rpmAverage.intVal[1]*2;
      }

      if (sensor == 1) average[1] += (int8_t) EEPROM.read(getCalibrationTableOffsetByValue(1, average[1]));
      min_val[sensor]= crete-5;
      lastMin[sensor]= millis() + 1000;
    }
  }

   
  //if (millis() - peak > 2000)
  //rpm = 0;

#ifdef DEBUG
  Serial.println(crete);
//  Serial.print(value[0]);
//  Serial.print(min_val[0]);
//  Serial.print("  ");
//  Serial.println(average[0]);
//  Serial.print(descentCount[0]);
//  Serial.println(descending[0]*1000);
//  Serial.print("  ");
//  Serial.println(descending[1]*1000);
//  Serial.println(value[1]);
//  Serial.println(min_val[1]);
//  Serial.println(average[1]);
//  Serial.println(rpm);
//  Serial.println(delta);
#endif

}

void do_raw_data() {
  setInterrupt(false);
  const int readings = 5;
  unsigned int value[NUM_SENSORS];
  unsigned long lastUpdateTime = millis();

    for (int sensor = 0; sensor < 2; sensor++) { //loop over all sensors
      lcd_setCursor(0, sensor * 3);
      lcd_print(F("min:"));
      lcd_setCursor(10, sensor * 3);
      lcd_print(F("max:"));
      min_val_raw[sensor]= 1024;
      max_val_raw[sensor]= 0;
    }
  while (!(buttonPressed() == CANCEL)) {
    for (int sensor = 0; sensor < 2; sensor++) { //loop over all sensors
      value[sensor]=readSensorRaw(sensor);
      value[1] += (int8_t) EEPROM.read(getCalibrationTableOffsetByValue(1, value[1]));
      if (value[sensor] < min_val_raw[sensor]) min_val_raw[sensor] = value[sensor];
      if (value[sensor] > max_val_raw[sensor]) max_val_raw[sensor] = value[sensor];
    }
    if (millis() - lastUpdateTime > refresh_r) {
      lcdBarsSmooth (value,1);
      for (int sensor = 0; sensor < 2; sensor++) { //loop over all sensors
        printLcdSpace(5, sensor * 3, 4);
        lcd_printFormatted(min_val_raw[sensor]); //display the difference between this sensor and master
        printLcdSpace(15, sensor * 3, 4);
        lcd_printFormatted(max_val_raw[sensor]); //display the difference between this sensor and master
      }
      lastUpdateTime = millis();
    }
  }

  crete = (min_val_raw[settings.master-1] + max_val_raw[settings.master-1])/2;
  lcd_clear();
  setInterrupt(true);
}

void lcdBarsCalib(unsigned int delta) {
  const uint8_t segmentsInCharacter = 5; //we need this number to make the display smooth

  byte bar[4][8];                         //store one custom character per bar

  char bars[DISPLAY_COLS + 1];          //store for the bar of full characters

  int range;          //store the range between the highest and lowest sensors
  int zoomFactor;                              //store the zoom of the display

  const uint8_t hysteresis = 4;

 // int TotalNumberOfLitSegments = delta; //determine the number of lit segments
  int TotalNumberOfLitSegments = constrain(delta,-50,50); //determine the number of lit segments
  int numberOfLitBars = TotalNumberOfLitSegments / segmentsInCharacter; //determine the number of whole characters
  int numberOfLitSegments = TotalNumberOfLitSegments
      % segmentsInCharacter;   //determine the remaining stripes

    makeCenterBars(bars, numberOfLitBars); //give us the bars of whole characters
    lcd_setCursor(0, 1);
    lcd_print(bars);                     //place the bars in the display

    makeChar(bars, numberOfLitSegments); //make a custom char for the remaining stripes
    lcd_createChar(1, bars);

    if (numberOfLitSegments > 0) {
      lcd_setCursor(10 + numberOfLitBars, 1); //place it on the right
    } else {
      lcd_setCursor(9 + numberOfLitBars, 1); //or in the center
    }
    if (numberOfLitBars < 10) lcd_write(byte(2));

}

// display centered bars, centered on the reference carb's reading, because that's the target we are aiming for
//takes an array of current average values for all sensors as parameter
void lcdBarsCenterSmooth(unsigned int value[]) {
  const uint8_t segmentsInCharacter = 5; //we need this number to make the display smooth

  byte bar[4][8];                         //store one custom character per bar

  char bars[DISPLAY_COLS + 1];          //store for the bar of full characters

  unsigned int maximumValue = maxVal(value); //determine the sensor with the highest average
  unsigned int minimumValue = minVal(value); //determine the lowest sensor average
  int range;          //store the range between the highest and lowest sensors
  int zoomFactor;                              //store the zoom of the display

  const uint8_t hysteresis = 4;

  //the range depends on finding the reading farthest from the master carb reading
  if (maximumValue - value[0]
      >= value[0] - minimumValue) {
    range = maximumValue - value[0];
  } else {
    range = value[0] - minimumValue;
  }

  //sets the minimum range before the display becomes 'pixelated' there are 100 segments available, 50 on either side of the master
  int ranges[] = { 50, 100, 150, 300, 512 };
  if (range < ranges[settings.zoom]) {
    range = ranges[settings.zoom];
  }

  zoomFactor = range / 50;

  for (int sensor = 0; sensor < 2; sensor++) { //for each of the sensors the user wants to use
    int delta = value[sensor] - value[0]; //find the difference between it and master
    int TotalNumberOfLitSegments = delta / zoomFactor; //determine the number of lit segments
    int numberOfLitBars = TotalNumberOfLitSegments / segmentsInCharacter; //determine the number of whole characters
    int numberOfLitSegments = TotalNumberOfLitSegments
        % segmentsInCharacter;   //determine the remaining stripes

    if (sensor == 1) { //for all sensors except the master carb sensor
      makeCenterBars(bars, numberOfLitBars); //give us the bars of whole characters
      lcd_setCursor(0, 1);
      lcd_print(bars);                     //place the bars in the display

      makeChar(bar[sensor], numberOfLitSegments); //make a custom char for the remaining stripes
      lcd_createChar(sensor + 2, bar[sensor]);

      if (numberOfLitSegments > 0) {
        lcd_setCursor(10 + numberOfLitBars, 1); //place it on the right
      } else {
        lcd_setCursor(9 + numberOfLitBars, 1); //or in the center
      }
      if (numberOfLitBars < 10)
        lcd_write(byte(sensor + 2));

        printLcdSpace(8, 2, 5);
        lcd_printFormatted(delta); //display the difference between this sensor and master
//      }
    }
  }

}

// this is used to display four plain non-zoomed bars with absolute pressure readings
void lcdBarsSmooth(unsigned int value[],int line) {
  const uint8_t segmentsInCharacter = 5;
  const uint8_t hysteresis = 2;

  byte bar[4][8];
  char bars[DISPLAY_COLS + 1];

  for (int sensor = 0; sensor < 2; sensor++) {
    //int TotalNumberOfLitSegments = 100000L / 1024 * value[sensor] / 1000; // integer math works faster, so we multiply by 1000 and divide later, powers of two would be even faster
    int TotalNumberOfLitSegments = constrain(map(value[sensor],300,600,0,65),0,65); // integer math works faster, so we multiply by 1000 and divide later, powers of two would be even faster
    int numberOfLitBars = TotalNumberOfLitSegments / segmentsInCharacter;
    int numberOfLitSegments = TotalNumberOfLitSegments
        % segmentsInCharacter;

    makeBars(bars, numberOfLitBars, 0); //skip function probably no longer needed
    lcd_setCursor(0, sensor + line);
    lcd_print(bars);

    makeChar(bar[sensor], numberOfLitSegments);
    lcd_createChar(sensor + 2, bar[sensor]);
    lcd_setCursor(numberOfLitBars, sensor + line);
    lcd_write(byte(sensor + 2));

    //if (!settings.silent) {
    //  if (numberOfLitBars < 10 - hysteresis)
        labelPosition = 14;
    //  if (numberOfLitBars > 10 + hysteresis)
    //    labelPosition = 0;
      printLcdSpace(labelPosition, sensor + line, 5);
      lcd_printFormatted(value[sensor]);
    //}
  }

}

//compares freshly loaded settings to the freshly saved verion, if there is a difference the save must have failed
//fail on write is the most common NVRAM failure by far
bool verifySettings() {
  settings_t settingsCopy = settings;
  settings = loadSettings(settingsCopy);
  return memcmp(&settings, &settingsCopy, sizeof(settings));
}

//saves our settings struct
void actionSaveSettings() {
  EEPROM.put(0, versionUID);  //only saves changed bytes!
  EEPROM.put(1, settingsOffset);
  EEPROM.put(settingsOffset, settings);  //only saves changed bytes!
  delay(500);  //eeprom settle time

  //Move our settings up 1 position and retry while memory lasts!
  if (0 != verifySettings()) {
    //if (settingsOffset + sizeof(settings) < 255)
    //  settingsOffset += sizeof(settings);
    //EEPROM.put(1, settingsOffset);
    actionSaveSettings();
    lcd_clear();
    lcd_setCursor(0, 1);
    lcd_print(F("SETTINGS WRITE ERROR"));
    lcd_setCursor(0, 2);
    lcd_print(F("SETTINGS RELOCATED"));
    waitForAnyKey();
  }
}

//loads the settings from EEPROM (Flash)
settings_t loadSettings(settings_t settings) {
  uint8_t compareVersion = 0;
  EEPROM.get(0, compareVersion);
  EEPROM.get(1, settingsOffset);

  if (compareVersion == versionUID) { //only load settings if saved by the current version, otherwise reset to 'factory' defaults
    settings = EEPROM.get(settingsOffset, settings);
  } else {
    settingsOffset = 2;
    settings = fetchFactoryDefaultSettings();
  }

  doContrast(settings.contrast);
  doBrightness(settings.brightness);
  return settings;
}

//does the display while clearing the calibration array
void doZeroCalibrations() {
  lcd_clear();
  lcd_setCursor(3, 1);
  lcd_print(txtWiping);
  zeroCalibrations();
  doConfirmation();
}

//determine where the calibration value is stored in EEPROM depending on the sample value
int getCalibrationTableOffsetByValue(int sensor, int value) {
  return calibrationOffset + ((sensor - 1) * numberOfCalibrationValues)
      + (value >> 2);
}

//determine where in EEPROM the calibration value is stored depending on the position
int getCalibrationTableOffsetByPosition(int sensor, int pos) {
  return calibrationOffset + ((sensor - 1) * numberOfCalibrationValues) + pos;
}

//only write if the value needs writing (saves write cycles)
void eepromWriteIfChanged(int address, int8_t data) {
  if ((uint8_t) data != EEPROM.read(address)) {
    EEPROM.write(address, (uint8_t) data);    //write the data to EEPROM
  }
}

int readSensorRaw(int sensor) {
  return (analogRead(inputPin[sensor]));
}

//clear the flash for a single sensor
void doClearCalibration(int sensor) {
  for (int i = 0; i < numberOfCalibrationValues; i++) {
    eepromWriteIfChanged(getCalibrationTableOffsetByPosition(sensor, i), 0); //write the data directly to EEPROM
  }
}

//actually clears the flash for all the sensors
void zeroCalibrations() {
  for (uint8_t sensor = 1; sensor < (NUM_SENSORS); sensor++) {
    doClearCalibration(sensor);
  }
}

void doClearCalibration1() {
  doClearCalibration(1);
  doConfirmation();
}

void doViewCalibration1() {
  doViewCalibration(1);
}

void doCalibrate1() {
  doCalibrate(1);
}

void doCalibrate(int sensor) {
  const int shift = 5;
  const int factor = 4;
  int maxValue = -127;
  int minValue = 127;
  int lowestCalibratedValue = 4096;
  int readingStandardPre, readingSensor, readingStandardPost;
  unsigned long lastUpdateTime = millis();
  unsigned long textChange = millis();
  bool calText = true;
  setInterrupt(false);

  lcd_clear();

  lcd_setCursor(0, 0);
  lcd_print(txtCalibrationBusy);
      
  lcd_setCursor(0, 3);
  lcd_print(txtPressAnyKey);
  displayKeyPressPrompt();

  delay(500); //otherwise key still pressed, probably need a better solution

  //initialize temp values array, note full ints (16 bits) used
  int values[numberOfCalibrationValues];

  //read existing values from EEPROM and pre-shift them
  //shifting an int left by n bits simply gives us n bits of 'virtual' decimal places
  // this is needed for accuracy because EMA calculation works by adding or subtracting relatively small values
  // which would otherwise all be truncated to '0'
  for (int i = 0; i < numberOfCalibrationValues; i++) {
    values[i] = (int8_t) EEPROM.read(
        getCalibrationTableOffsetByPosition(sensor, i));
    values[i] <<= shift;
  }

  while (!buttonPressed()) {
    readingStandardPre = readSensorRaw(0);  //read master
    readingSensor = readSensorRaw(1); //read calibration sensor
    readingStandardPost = readSensorRaw(0);  //read master again

    int readingStandard = (readingStandardPre + readingStandardPost) >> 1; //average both to increase accuracy on slopes
    int calibrationValue = readingStandard - readingSensor;

    //record some basic quality statistics
    maxValue = max (calibrationValue , maxValue);
    minValue = min (calibrationValue , minValue);
    lowestCalibratedValue = min (readingSensor , lowestCalibratedValue);
    
    values[(readingSensor >> 2)] = intExponentialMovingAverage(shift,
        factor, values[(readingSensor >> 2)], calibrationValue);

    if (millis() - textChange > 2000){
      calText = !calText;
      printLcdSpace(0, 0, 19);
      if (calText) lcd_print(txtCalibrationBusy);
      else lcd_print(txtCalibrationBusy2);
      textChange = millis();
    }
    
    if (millis() - lastUpdateTime > refresh_r) {
      lcdBarsCalib(calibrationValue);      
      lcd_setCursor(0, 0);

      printLcdSpace(1, 2, 4);
      lcd_printFormatted(readingStandard); //display the difference between this sensor and master

      printLcdSpace(8, 2, 4);
      lcd_printFormatted(readingSensor); //display the difference between this sensor and master

      printLcdSpace(15, 2, 4);
      lcd_printFormatted(calibrationValue); //display the difference between this sensor and master

      lastUpdateTime = millis();
    }

  }

  //post_shift the values in preparation of writing back to EEPROM
  // we don't need to save the 'decimal places' because they are not needed anymore.
  // so we lose them by shifting them out of range to the right
  for (int i = 0; i < numberOfCalibrationValues; i++) {
    values[i] >>= shift;
  }

  //save calibrations
  for (int i = 0; i < numberOfCalibrationValues; i++) {
    eepromWriteIfChanged(getCalibrationTableOffsetByPosition(sensor, i),
        (int8_t) values[i]);
  }

  lcd_clear();

  lcd_setCursor(0, 0);
  lcd_print(txtCalibrationDone);

  lcd_setCursor(0, 1);
  lcd_print(txtLowestPressure);
  printLcdInteger(lowestCalibratedValue, 15, 1, 4);
  lcd_setCursor(0, 2);
  lcd_print(txtMinAdjust);
  printLcdInteger(minValue, 16, 2, 3);
  lcd_setCursor(0, 3);
  lcd_print(txtMaxAdjust);
  printLcdInteger(maxValue, 16, 3, 3);

  waitForAnyKey();
  displayCalibratedValues(values);
  setInterrupt(true);
}

void doViewCalibration(int sensor) {
  setInterrupt(false);
  int values[numberOfCalibrationValues];

  for (int i = 0; i < numberOfCalibrationValues; i++) {
    values[i] = (int8_t) EEPROM.read(
        getCalibrationTableOffsetByPosition(sensor, i));
  }

  displayCalibratedValues(values);
  setInterrupt(true);
}

//display indicator arrows and numeric offsets so we don't get lost in the graph of calibration values.
void displayNavArrowsAndOffsets(int valueOffset,
    bool topLeftArrowPositionAvailable,
    bool topRightArrowPositionAvailable) {
  if (valueOffset == 0) {
    (topLeftArrowPositionAvailable) ?
        lcd_setCursor(0, 0) : lcd_setCursor(0, 3);
    lcd_printChar('[');
    lcd_printInt(valueOffset);
  }
  if (valueOffset > 0) {
    (topLeftArrowPositionAvailable) ?
        lcd_setCursor(0, 0) : lcd_setCursor(0, 3);
    lcd_printChar(char(MENUCARET + 1)); //little arrow to the left
    lcd_printInt(valueOffset);
  }
  if (valueOffset == numberOfCalibrationValues - 20) {
    (topRightArrowPositionAvailable) ?
        lcd_setCursor(16, 0) : lcd_setCursor(16, 3);
    lcd_printInt(valueOffset + 20);
    lcd_printChar(']');
  }
  if (valueOffset < numberOfCalibrationValues - 20) {
    (topRightArrowPositionAvailable) ?
        lcd_setCursor(16, 0) : lcd_setCursor(16, 3);
    if ((valueOffset + 20) < 100)
      lcd_printChar(' ');

    lcd_printInt(valueOffset + 20);
    lcd_printChar(char(MENUCARET)); //little arrow to the right
  }
}

// Show a graph of the computed calibration values so the user can get an idea of the quality of the sensors
// and of the calibration. Repeated calibration increases the accuracy.
// Note: if all sensors are showing the same type of displacement that means that sensor 0
// is off by that much in the opposite direction.
void displayCalibratedValues(int values[]) {
  int valueOffset = 0;
  int numberOfColumns = 20;
  int segmentsPerCharacter = 8;
  int numberOfCharacters = 4;
  int numberOfSegments = segmentsPerCharacter * (numberOfCharacters / 2);
  int valuePerSegment = settings.calibrationMax / numberOfSegments; //128 / 16 = 8
  int pressedButton = 0;
  bool dataChanged = true;
  bool topLeftArrowPositionAvailable, topRightArrowPositionAvailable = true;
  makeCalibrationChars();

  while (pressedButton != CANCEL) {
    if (dataChanged) {
      lcd_clear();
      for (int column = 0; column < numberOfColumns; column++) {
        int valueInSegments = values[valueOffset + column]
            / valuePerSegment;

        if (valueInSegments <= segmentsPerCharacter
            && valueInSegments > 0) {
          lcd_setCursor(column, 1);
          lcd_write(byte((byte) 8 - valueInSegments));
        } else if (valueInSegments > 2 * segmentsPerCharacter) {
          lcd_setCursor(column, 0);
          lcd_printChar('|');
          lcd_setCursor(column, 1);
          lcd_printChar('|');
        } else if (valueInSegments > segmentsPerCharacter) {
          lcd_setCursor(column, 0);
          lcd_write(
              byte(
                  (byte) 8
                      - (valueInSegments
                          % segmentsPerCharacter)));
        } else if (valueInSegments < (2 * -segmentsPerCharacter)) {
          lcd_setCursor(column, 2);
          lcd_printChar('|');
          lcd_setCursor(column, 3);
          lcd_printChar('|');
        } else if (valueInSegments < 0
            && (valueInSegments >= -segmentsPerCharacter)) {
          lcd_setCursor(column, 2);
          lcd_write(byte((byte) (-valueInSegments) - 1));
        } else if (valueInSegments < 0
            && (valueInSegments < -segmentsPerCharacter)) {
          lcd_setCursor(column, 3);
          lcd_write(
              byte(
                  (byte) 8
                      - ((valueInSegments + 1)
                          % segmentsPerCharacter)));
        }

        if (column == 0)
          topLeftArrowPositionAvailable = (valueInSegments <= 0);
        if (column == 19)
          topRightArrowPositionAvailable = (valueInSegments <= 0);

      }

      //show arrows to indicate scrolling and our location in the calibration array
      displayNavArrowsAndOffsets(valueOffset,
          topLeftArrowPositionAvailable,
          topRightArrowPositionAvailable);
    }

    //allow the user to scroll through the values from left to right and vice versa
    pressedButton = buttonPressed();
    if ((pressedButton == LEFT) && (valueOffset > 20)) {
      valueOffset -= 20;
      dataChanged = true;
    } else if ((pressedButton == LEFT) && (valueOffset <= 20)) {
      valueOffset = 0;
      dataChanged = true;
    } else if ((pressedButton == RIGHT)
        && (valueOffset < numberOfCalibrationValues - 20 - 20)) {
      valueOffset = (valueOffset + 20);
      dataChanged = true;
    } else if ((pressedButton == RIGHT)
        && (valueOffset >= numberOfCalibrationValues - 20 - 20)) {
      valueOffset = (numberOfCalibrationValues - 20);
      dataChanged = true;
    } else {
      dataChanged = false;
    }
  }
}

//create special characters in LCD memory these contain the horizontal lines
// we use to generate a graph of our calibration data
// using simple lines instead of full bars means we can use the same characters above and below zero
// because we only have 8 special chars, we would run out if we used bars!
void createSpecialCharacter(int number) {
  byte specialCharacter[8];

  for (int i = 0; i < 8; i++) {
    specialCharacter[i] = 0b00000;
  }
  specialCharacter[number - 1] = 0b11111;
  lcd_createChar(number - 1, specialCharacter);
}

// we need 8 characters to use each line in a 5x8 pixel character cell
void makeCalibrationChars() {
  for (int i = 1; i <= 8; i++) {
    createSpecialCharacter(i);
  }
}

void makeCenterBars(char *bars, int8_t number) {
  if (number > 10)
    number = 10;
  if (number < -10)
    number = -10;

  if (number < 0) {
    for (int8_t i = 0; i < 10 + number; i++) {
      bars[i] = ' ';
    }
    for (int8_t i = 10 + number; i < 10; i++) {
      bars[i] = 0xff;
    }
    for (int8_t i = 10; i < 20; i++) {
      bars[i] = ' ';
    }
  }

  if (number == 0) {
    for (int8_t i = 0; i <= 20; i++) {
      bars[i] = ' ';
    }
  }

  if (number > 0) {
    for (int8_t i = 0; i <= 10; i++) {
      bars[i] = ' ';
    }
    for (int8_t i = 10; i <= 10 + number; i++) {
      bars[i] = 0xff;
    }
    for (int8_t i = 10 + number; i < 20; i++) {
      bars[i] = ' ';
    }
  }

  bars[DISPLAY_COLS] = 0x00;
}

//used to detect ambient pressure for readings that ascend with vacuum in stead of going down toward absolute 0 pressure
int detectAmbient() {
  unsigned long total = 0;
  uint8_t numberOfSamples = 200;        //set the number of samples to average

  for (int i = 0; i < numberOfSamples; i++) {

    total += readSensorRaw(0);                      //add the reading we got
  }
  return total / numberOfSamples; //divide the result by the number of samples for the resulting average
}

ISR(TIMER1_COMPA_vect) {
  intRunningAverage();
}