lightmeter/lightmeter.ino

//STM32F103C,  64k flash
//upload method: serial (A9 to RX, A10 to TX)
//To upload set Boot0 jumper to 1 (the one further away from reset btn) and press reset (stm will boot from flash wich contains uart to flash uploader)
//upload via arduino IDE
//To boot program after restart set Boot0 jumper to 0

//Letters 5x7 at Size 1


//#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h> // http://www.instructables.com/id/Monochrome-096-i2c-OLED-display-with-arduino-SSD13/
//128 x 64 px

#include <BH1750.h>   //from: https://github.com/mysensors/MySensorsArduinoExamples/tree/master/libraries/BH1750
BH1750 lightMeter;

#define PIN_LDR 0 //A0
#define PIN_BRIGHTMODE 1 //A1
#define PIN_VBAT 2 //A2

#define PIN_TRIGGER PB8
#define PIN_BTNLEFT PA15
#define PIN_BTNCENTER PB4
#define PIN_BTNRIGHT PB5

#define PIN_ON PB9
#define TIME_AUTOPOWEROFF 120000
#define LDRDELAY 50 //minimum delay between ldr readings. Transistor for lower value pulldown resistor switches in between
#define INCIDENTDELAY 100 //minimum delay between incident sensor (BH1750) readings
#define DEBOUNCETIME 50 //time to not check for inputs after key press
#define BUTTONTIMEHOLD 750 //time for button hold

#define voltage_warn 3.4 //voltage per cell   //TODO implement warning

//float shuttertimes1[]={1,1.0/2, 1.0/4, 1.0/8, 1.0/15, 1.0/30, 1.0/60, 1.0/125, 1.0/250, 1.0/500, 1.0/1000, 1.0/2000, 1.0/4000, 1.0/8000};
float shuttertimes1[]={64,32,16,8,4,2,1,1.0/2, 1.0/4, 1.0/8, 1.0/15, 1.0/30, 1.0/60, 1.0/125, 1.0/250, 1.0/500, 1.0/1000, 1.0/2000, 1.0/4000, 1.0/8000};
#define SHUTTERTIMES1_MAXINDEX 19
String settingsnameShutterSelectionMode[]={"Analog"}; //names for tables
#define MAXIMUM_SHUTTERSELECTIONMODES 1

float aperaturesFull[]={1,1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32};
#define APERATURESFULL_MAXINDEX 10
float aperaturesHalf[]={1, 1.2, 1.4, 1.7, 2, 2.4, 2.8, 3.4, 4, 4.8, 5.6, 6.7, 8, 9.5, 11, 13, 16, 19, 22};
#define APERATURESHALF_MAXINDEX 18
float aperaturesThird[]={1, 1.1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.5, 2.8, 3.2, 3.5, 4, 4.5, 5.0, 5.6, 6.3, 7.1, 8, 9, 10, 11, 13, 14, 16, 18, 20, 22, 25, 29, 32, 36, 40, 45};
#define APERATURESTHIRD_MAXINDEX 33
String settingsnameAperatureSelectionMode[]={"Full","Half","Third"}; //names for tables
#define MAXIMUM_APERATURESELECTIONMODES 3

float isoFull[]={12,25,50,100,200,400,800,1600,3200,6400,12500,25600};
float isoThird[]={12,16,20,25,32,40,50,64,80,100,125,160,200,250,320,400,500,640,800,1000,1250,1600,2000,2500,3200,4000,5000,6400,8000,10000,12500,16000,20000,25600};



long loopmillis=0; //only use one millis reading each loop
long last_ldrReading=0;
long last_incidentReading=0;
long millis_lastchange=0;
long millis_lastinput=0;

long timebuttonpressed_trigger;
long timebuttonpressed_left;
long timebuttonpressed_center;
long timebuttonpressed_right;

//Short press (true when button short pressed, on release)
boolean button_trigger=false;
boolean button_left=false;
boolean button_center=false;
boolean button_right=false;

//long press (true when button is held down for BUTTONTIMEHOLD, on time elapsed)
boolean button_hold_trigger=false;
boolean button_hold_left=false;
boolean button_hold_center=false;
boolean button_hold_right=false;

float vbat=0;

struct Settings {
  uint8_t minimumAperatureIndex; //see corresponding aperatures table
  uint8_t aperatureSelectionMode; //1=Full, 2=Half, 3=Third
  uint8_t shutterSelectionMode; //index for which shuttertimes table to use
  uint8_t ISOSelectionMode; //1=Full, 2=Thirds
};

Settings userSettings= {1,1, 1,2};




#define OLED_RESET 4
Adafruit_SSD1306 display(OLED_RESET);

uint16_t incident=0; //incident reading from bh1750
uint16_t analog_low=0; //better for low light
uint16_t analog_high=0; //better for bright light (higher pulldown resistor for ldr)
float ev=0; //calculated EV from LDR readings (reflected) or from Luxmeter (incident)

float ev_min=6,ev_max=12,ev_last=8;

float showAperature=0;
float showShutter=0;

//Usersettings
float setAperature=8; //set to use aperature. 0 for auto
float setShutter=0; //set to use shutter time, 0 for auto
uint16_t setISO=100; //set to ISO

enum displaymode {
  lightmeter,
  settings
};
displaymode displaymode=lightmeter;
uint8_t settings_selectedItem=0; //in settings display
String settingStrings[]={"ISO:","F-Stops:","Timetable:","Turn Off"};
#define SETTINGS_SELECTEDITEM_MAX 3 //inclusive. 2 means 3 items available
boolean settings_itemActive=false; //item in settings selected to change value

#define METERINGMODE_REFLECTIVE 0
#define METERINGMODE_INCIDENT 1
uint8_t meteringmode=METERINGMODE_REFLECTIVE;


char tempstring[16]; //for dtostrf  //dtostrf(modefactor,1,3,tempstring);

#if (SSD1306_LCDHEIGHT != 64)
#error("Height incorrect, please fix Adafruit_SSD1306.h!");
#endif

void setup()   {                
  Serial.begin(9600);
  Serial.println("Started");

  Serial.println("Init Display");
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
  display.display();

  Serial.println("Init BH1750");
  lightMeter.begin(BH1750_CONTINUOUS_HIGH_RES_MODE_2); //max reading=54612
  //set measurement time (for higher resolution) http://www.raspberry-pi-geek.de/Magazin/2015/04/Digital-Light-Sensor-BH1750-am-Raspberry-Pi
  //lightMeter.write8(71); //01000111 //high bit: 01000xxx   bits 7,6,5
  //lightMeter.write8(126); //01111110 //log bit: 011xxxxx   bits 4,3,2,1,0

  pinMode(PIN_LDR, INPUT_ANALOG);
  pinMode(PIN_VBAT, INPUT_ANALOG);
  pinMode(PIN_TRIGGER, INPUT_PULLUP);
  pinMode(PIN_BTNLEFT, INPUT_PULLUP);
  pinMode(PIN_BTNCENTER, INPUT_PULLUP);
  pinMode(PIN_BTNRIGHT, INPUT_PULLUP);
  pinMode(PIN_BRIGHTMODE, OUTPUT);
  digitalWrite(PIN_BRIGHTMODE, LOW);
  pinMode(PIN_ON, OUTPUT);
  digitalWrite(PIN_ON, HIGH);
  millis_lastchange=millis();

  
  Serial.println("Initialized");


  //display.drawPixel(10, 10, WHITE);
  
}


void loop() {
  loopmillis=millis(); //read millis for this cycle


  
  handleInputs();
  
  calculateEV();

  updateDisplay();

  

}


void handleInputs()
{
  //Short press (true when button short pressed, on release)
  button_trigger=false;
  button_left=false;
  button_center=false;
  button_right=false;

  //long press (true when button is held down for BUTTONTIMEHOLD, on time elapsed)
  button_hold_trigger=false;
  button_hold_left=false;
  button_hold_center=false;
  button_hold_right=false;

  if (millis()-millis_lastinput>DEBOUNCETIME) //Button debouncing
  {
    //Trigger
    if (timebuttonpressed_trigger == 0 && !digitalRead(PIN_TRIGGER)){ //first time pressed down. (low when pressed)
      timebuttonpressed_trigger=loopmillis; //set time of button press
    }else if(timebuttonpressed_trigger != 0 && digitalRead(PIN_TRIGGER)){ //button released (was pressed)
      if (loopmillis-timebuttonpressed_trigger < BUTTONTIMEHOLD){ //short press
        button_trigger=true;
      }
      timebuttonpressed_trigger=0; //re-enable after short press and release from hold
    }else if(loopmillis-timebuttonpressed_trigger >= BUTTONTIMEHOLD && timebuttonpressed_trigger>0){ //held down long enough and not already hold triggered
      button_hold_trigger=true;
      timebuttonpressed_trigger=-1; //-1 as flag for hold triggered
    }
  
    //Left
    if (timebuttonpressed_left == 0 && !digitalRead(PIN_BTNLEFT)){ //first time pressed down. (low when pressed)
      timebuttonpressed_left=loopmillis; //set time of button press
    }else if(timebuttonpressed_left != 0 && digitalRead(PIN_BTNLEFT)){ //button released (was pressed)
      if (loopmillis-timebuttonpressed_left < BUTTONTIMEHOLD){ //short press
        button_left=true;
      }
      timebuttonpressed_left=0; //re-enable after short press and release from hold
    }else if(loopmillis-timebuttonpressed_left >= BUTTONTIMEHOLD && timebuttonpressed_left>0){ //held down long enough and not already hold triggered
      button_hold_left=true;
      timebuttonpressed_left=-1; //-1 as flag for hold triggered
    }
  
    //Center
    if (timebuttonpressed_center == 0 && !digitalRead(PIN_BTNCENTER)){ //first time pressed down. (low when pressed)
      timebuttonpressed_center=loopmillis; //set time of button press
    }else if(timebuttonpressed_center != 0 && digitalRead(PIN_BTNCENTER)){ //button released (was pressed)
      if (loopmillis-timebuttonpressed_center < BUTTONTIMEHOLD){ //short press
        button_center=true;
      }
      timebuttonpressed_center=0; //re-enable after short press and release from hold
    }else if(loopmillis-timebuttonpressed_center >= BUTTONTIMEHOLD && timebuttonpressed_center>0){ //held down long enough and not already hold triggered
      button_hold_center=true;
      timebuttonpressed_center=-1; //-1 as flag for hold triggered
    }
  
    //Right
    if (timebuttonpressed_right == 0 && !digitalRead(PIN_BTNRIGHT)){ //first time pressed down. (low when pressed)
      timebuttonpressed_right=loopmillis; //set time of button press
    }else if(timebuttonpressed_right != 0 && digitalRead(PIN_BTNRIGHT)){ //button released (was pressed)
      if (loopmillis-timebuttonpressed_right < BUTTONTIMEHOLD){ //short press
        button_right=true;
      }
      timebuttonpressed_right=0; //re-enable after short press and release from hold
    }else if(loopmillis-timebuttonpressed_right >= BUTTONTIMEHOLD && timebuttonpressed_right>0){ //held down long enough and not already hold triggered
      button_hold_right=true;
      timebuttonpressed_right=-1; //-1 as flag for hold triggered
    }
  }

  /*
  if (button_trigger || button_left || button_center || button_right){
  Serial.println("Buttons short:");
  Serial.print(button_trigger);
  Serial.print(button_left);
  Serial.print(button_center);
  Serial.println(button_right);
  }
  if (button_hold_trigger || button_hold_left || button_hold_center || button_hold_right){
  Serial.println("Buttons long:");
  Serial.print(button_hold_trigger);
  Serial.print(button_hold_left);
  Serial.print(button_hold_center);
  Serial.println(button_hold_right);
  }
  */
  
  //Voltage
  vbat=map(analogRead(PIN_VBAT), 0,3910,0,8400)/1000.0; //180k and 300k voltage divider. 8,4V -> 3,15V=3910

  //LDR
  if ( loopmillis-last_ldrReading>LDRDELAY )
  {
    if (!digitalRead(PIN_BRIGHTMODE)){
      analog_low=analogRead(PIN_LDR);
    }else{
      analog_high=analogRead(PIN_LDR);
    }
    digitalWrite(PIN_BRIGHTMODE, !digitalRead(PIN_BRIGHTMODE)); //switch modes
    last_ldrReading=loopmillis;
  }

  

  //Lightsensor BH1750
  if ( loopmillis-last_incidentReading>INCIDENTDELAY )
  {
    incident = lightMeter.readLightLevel(); //value in lux from sensor
    last_incidentReading=loopmillis;
  }
  

  
  //Test  asdf
  /*
  if ( !digitalRead(PIN_TRIGGER)  ) {
    Serial.println("roundAperature");
    for (float i=0.1;i<30;i+=0.5){
      Serial.print(i);
      Serial.print(" -> ");
      Serial.println(roundAperature(i,1));
    }
    Serial.println("roundShutter");
    for (float i=1.0/8000;i<32;i*=2){
      Serial.print(i,6);
      Serial.print(" -> ");
      Serial.print(roundShutter(i,1),6);
      Serial.print(" -- ");
      Serial.println(reciprocFloat(roundShutter(i,1))); 
    }
    

    Serial.println("calculateShutter at iso 100 f8");
    for (int8_t i=-2;i<18;i++){
      Serial.print(i);
      Serial.print(" -> ");
      Serial.println(calculateShutter(i, (uint16_t)100, 8.0),6);
    }

    Serial.println("calculateAperature at iso 100 1/125s");
    for (int8_t i=-2;i<18;i++){
      Serial.print(i);
      Serial.print(" -> ");
      Serial.println(calculateAperature(i, (uint16_t)100, 1.0/125),6);
    }
    
  }
  */


  switch(displaymode){
    case lightmeter:
      handleInputs_Lightmeter();
      break;
    case settings:
      handleInputs_Settings();
      break;
  }
  
  

  if (millis()-millis_lastchange>TIME_AUTOPOWEROFF){
    digitalWrite(PIN_ON, LOW);
  }

  if ( button_trigger || button_left || button_center || button_right ) {
    millis_lastchange=millis(); //for auto poweroff
    millis_lastinput=millis(); //for debouncing
  }
  
}

void handleInputs_Lightmeter()
{
  if ( button_hold_center  ) { //Go to Settings
    displaymode=settings;
  }
  if ( button_center )  { //Change Refelctive - Incident
    if (meteringmode == METERINGMODE_REFLECTIVE){
      meteringmode = METERINGMODE_INCIDENT;
    }else if (meteringmode == METERINGMODE_INCIDENT) {
      meteringmode = METERINGMODE_REFLECTIVE;
    }
  }
  
  if (setShutter==0 && setAperature==0){ //Auto
    //Value Change
    if ( button_left  ) {
      
    }
    if ( button_right  ) {
      
    }
    //Change Mode
    if ( button_hold_left ){ //Auto -> T
      setShutter=showShutter;
      setAperature=0;
    }
    if ( button_hold_right ){ //Auto -> Av
      setAperature=showAperature;
      setShutter=0;
    }
  }else if(setShutter==0){ //Aperature Priority
    //Value Change
    if ( button_left  ) {
      changeAperature(1); //Decrement Aperature
    }
    if ( button_right  ) {
      changeAperature(-1); //Increment Aperature
    }
    //Change Mode
    if ( button_hold_left ){ //change from Aperature Priority to Auto, Av -> Auto
      setAperature=0;
      setShutter=0;
    }
    if ( button_hold_right ){ //Av -> T
      setShutter=showShutter;
      setAperature=0;
    }
  }else if (setAperature==0){ //Shutter Priority
    //Value Change
    if ( button_left  ) {
      changeShutter(1); //Decrement Aperature
    }
    if ( button_right  ) {
      changeShutter(-1); //Increment Aperature
    }
    //Change Mode
    if ( button_hold_left ){ //T -> Av
      setAperature=showAperature;
      setShutter=0;
    }
    if ( button_hold_right ){ //T -> Auto
      setAperature=0;
      setShutter=0;
    }
  }

  
}


void handleInputs_Settings()
{
  if ( button_hold_center  ) { //Go to Lightmeter
    displaymode=lightmeter;
  }

  

  if (!settings_itemActive){ //select items
    if ( button_left  ) {
      if (settings_selectedItem>0){ //not first item
        settings_selectedItem-=1;
      }
    }
    if ( button_right  ) {
      if (settings_selectedItem<SETTINGS_SELECTEDITEM_MAX){ //not last item
        settings_selectedItem+=1;
      }
    }
    if ( button_center ){
      settings_itemActive=true; //select item to change value
    }
    
  }else{  //item selected to change value
    
    switch (settings_selectedItem)
    {
      case 0: //ISO
        if ( button_left  ) {
          changeISO(-1);
        }
        if ( button_right  ) {
          changeISO(1);
        }
        break;

      case 1: //Aperature Selection Mode
        if ( button_left  ) {
          if(userSettings.aperatureSelectionMode>1){
            userSettings.aperatureSelectionMode-=1;
          }
        }
        if ( button_right  ) {
          if (userSettings.aperatureSelectionMode<MAXIMUM_APERATURESELECTIONMODES){
            userSettings.aperatureSelectionMode+=1;
          }
        }
        break;

      case 2: //Shutter Selection Mode
        if ( button_left  ) {
          if(userSettings.shutterSelectionMode>1){
            userSettings.shutterSelectionMode-=1;
          }
        }
        if ( button_right  ) {
          if (userSettings.shutterSelectionMode<MAXIMUM_SHUTTERSELECTIONMODES){
            userSettings.shutterSelectionMode+=1;
          }
        }
        break;

      case 3: //Turn Off
        digitalWrite(PIN_ON, LOW); //set power latch low
        break;
    }
    if ( button_center ){
      settings_itemActive=false; //return to item selection
    }
  }
  
}

float reciprocFloat(float p){
  if (p<1){
    return   (1.0f/( (int)(p*1000000) ) )*1000000 ;
  }else{
    return (1/p);
  }
}

void calculateEV()
{
  if (meteringmode == METERINGMODE_REFLECTIVE){
    //ev=map(analog_low,500, 3500 ,500, 1400)/100.0; //for testing
    double highev=11.7400532 + 0.000216655133*analog_high + 0.00000111372253*pow(analog_high,2) + -0.000000000163800818 *pow(analog_high,3);
    double lowev=-0.763427709 + 0.0138031137*analog_low + -0.00000576990095*pow(analog_low,2) + 0.000000000871611285*pow(analog_low,3);
  
    if (lowev>14){
      ev=highev;
    }else if(lowev<12.5){
      ev=lowev;
    }else{ //mix of both
      float mix=min(1.0, max(0.0,(lowev-12.5)/(14-12.5))); //0 to 1, 0-> use only lowev, 1-> use only highev
      ev=lowev*(1-mix)+highev*mix;
    }
  }else if (meteringmode == METERINGMODE_INCIDENT){
    ev = luxToEv(incident);
  }

  if (setAperature>0){ //Aperature Priority
    showAperature=setAperature; //use user set Aperature
    showShutter=calculateShutter(ev,setISO, setAperature);
  }else if(setShutter>0){ //Shutter Priority
    showShutter=setShutter; //use user set Shutter
    showAperature=calculateAperature(ev, setISO, setShutter);
  }else{ //Auto
    //TODO
    showAperature=42;
    showShutter=42;
  }
  
}

double evToLux(double ev) {
    return pow(2, ev) * 2.5;
}
double luxToEv(uint16_t lux){
  if (lux <= 2){
    return 0;
  }
  return log (lux/2.5) / log (2);
}

float calculateShutter(float pEv, uint16_t pIso, uint16_t pAperature) //returns calculated Shutter speed given Ev, ISO and Aperature
{
  //EV = log2 ( 100* Aperature^2 / (ISO * Time ))
  //100* Aperature^2 / (2^EV * ISO) =  Time
  return (100.0 * pow( pAperature,2) ) / (pow(2,pEv)*pIso);
}
float calculateAperature(float pEv, uint16_t pIso, float pShutter) //returns mathematical aperature in x1
{
  //EV = log2 ( 100* Aperature^2 / (ISO * Time ))
  // sqrt( 2^EV *(ISO * Time ) /100 ) = Aperature
  return sqrt( pow(2,pEv) * pIso * pShutter / 100.0 ) ;
}
float roundShutter(float pShutter, uint8_t pMethod) //round shutter to typical values
{
  uint8_t _index=findShutterIndex(pShutter,pMethod);
  
  //use closest shutter value
  switch(pMethod){
  case 1: //
      return shuttertimes1[_index];
    break;
  }
}

float roundAperature(float pAperature, uint8_t pMethod) //round Aperature (x1) to typical values. method=0 -> leave, 1=full stops, 2=half stops, 3=third stops
{
  if (pMethod==0){
    return pAperature;
  }
  
  uint8_t closest_index=findAperatureIndex(pAperature,pMethod);
  
  //use closest aperature value
  switch(pMethod){
    case 1: //full stops
        return aperaturesFull[closest_index];
      break;
    case 2: //half stops
        //return float ( pow(sqrt(sqrt(2)), _index-2) );
        return aperaturesHalf[closest_index];
      break;
    case 3: //third stops
        return aperaturesThird[closest_index];
        //return float ( pow(cbrt(sqrt(2)), _index-2) );
      break;
  }
}

void changeAperature(int8_t pchange){ //pchange>0 means more light exposure (brighter image)
  uint8_t _newAperatureIndex=findAperatureIndex(setAperature,userSettings.aperatureSelectionMode);

  uint8_t _maximumAperatureIndex=0;
  switch(userSettings.aperatureSelectionMode){ //check max
    case 1: //full stops
        _maximumAperatureIndex=sizeof(aperaturesFull)/sizeof(float); 
      break;
    case 2: //half stops
        _maximumAperatureIndex=sizeof(aperaturesHalf)/sizeof(float);
      break;
    case 3: //third stops
        _maximumAperatureIndex=sizeof(aperaturesThird)/sizeof(float);
      break;
  }
  _newAperatureIndex-=pchange; //change aperature
  _newAperatureIndex=min(_newAperatureIndex,_maximumAperatureIndex-1); //maximum limit
  _newAperatureIndex=max(_newAperatureIndex,userSettings.minimumAperatureIndex); //minimum limit
  
  switch(userSettings.aperatureSelectionMode){
    case 1: //full stops
        setAperature=aperaturesFull[_newAperatureIndex];
      break;
    case 2: //half stops
        setAperature=aperaturesHalf[_newAperatureIndex];
      break;
    case 3: //third stops
        setAperature=aperaturesThird[_newAperatureIndex];
      break;
  }
}
uint8_t findAperatureIndex(float pAperature,uint8_t pMethod) //find index of closest aperature from given aperature tables (pMethod
{
  float _minDistance=90000;
  float _lastminDistance=100000;
  uint8_t _index=userSettings.minimumAperatureIndex;
  uint8_t _maxindexpossible=0;
  
  switch(pMethod){
    case 1:
        _maxindexpossible=APERATURESFULL_MAXINDEX;
      break;
    case 2:
        _maxindexpossible=APERATURESHALF_MAXINDEX;
      break;
    case 3:
        _maxindexpossible=APERATURESTHIRD_MAXINDEX;
      break;
  }

  while (_lastminDistance>_minDistance) //until distance increases
  {
    if (_index>_maxindexpossible){ //this index will be out of bounds
      return _maxindexpossible;
    }
    
    _lastminDistance=_minDistance;
    
    switch(pMethod){
    case 1: //full stops
        _minDistance=abs( pAperature - aperaturesFull[_index] );
      break;
    case 2: //half stops
        _minDistance=abs( pAperature - aperaturesHalf[_index] );
      break;
    case 3: //third stops
        _minDistance=abs( pAperature - aperaturesThird[_index] );
      break;
    }
    _index++; //next
  }
  
  return _index-2; //use index with closest value
}


void changeShutter(int8_t pchange){ //pchange>0 means more light exposure (brighter image)
  
  
  uint8_t _newShutterIndex=findShutterIndex(setShutter,userSettings.shutterSelectionMode);

  uint8_t _maximumShutterIndex=0;
  switch(userSettings.shutterSelectionMode){ //get max index from array
    case 1:
        _maximumShutterIndex=sizeof(shuttertimes1)/sizeof(float);
      break;
  }
  
  if (!( -pchange<0 && _newShutterIndex==0)){ //changed value would not yield negative index
    _newShutterIndex-=pchange; //change aperature
    _newShutterIndex=min(_newShutterIndex,_maximumShutterIndex-1); //maximum limit from array
    //_newShutterIndex=min(_newShutterIndex,maximumShutterIndex); //maximum limit from user settings
  }
  
  switch(userSettings.shutterSelectionMode){
    case 1: //
        setShutter=shuttertimes1[_newShutterIndex];
      break;
  }
}
uint8_t findShutterIndex(float pShutter,uint8_t pMethod) //find index of closest aperature from given aperature tables (pMethod
{
  float _minDistance=abs(pShutter-shuttertimes1[0]);
  float _lastminDistance=_minDistance;
  uint8_t _index=0;
  uint8_t _maxindexpossible=0;
  
  switch(pMethod){
    case 1:
        _maxindexpossible=SHUTTERTIMES1_MAXINDEX;
      break;
  }

  
  while (_lastminDistance>=_minDistance) //until distance increases
  {
    if (_index>_maxindexpossible){ //this index will be out of bounds
      return _maxindexpossible;
    }
    
    _lastminDistance=_minDistance;
    
    switch(pMethod){
    case 1:
        _minDistance=abs(pShutter - shuttertimes1[_index]);
      break;
    }
    _index++; //next
  }
  
  return _index-2; //use index with closest value
}

void changeISO(int8_t pchange){ //pchange>0 means more light exposure (brighter image), higher iso
  
  
  uint8_t _newISOIndex=findISOIndex(setISO,userSettings.ISOSelectionMode);

  uint8_t _maximumISOIndex=0;
  switch(userSettings.ISOSelectionMode){ //get max index from array
    case 1:
        _maximumISOIndex=sizeof(isoFull)/sizeof(float);
      break;
    case 2:
        _maximumISOIndex=sizeof(isoThird)/sizeof(float);
      break;
  }
  if (!( pchange<0 && _newISOIndex==0)){ //changed value would not yield negative index
    _newISOIndex+=pchange; //change iso
    _newISOIndex=min(_newISOIndex,_maximumISOIndex-1); //maximum limit from array
    //_newISOIndex=min(_newISOIndex,maximumISOIndex); //maximum limit from user settings
  }
  
  switch(userSettings.ISOSelectionMode){
    case 1: //
        setISO=isoFull[_newISOIndex];
      break;
    case 2: //
        setISO=isoThird[_newISOIndex];
      break;
  }
}

uint8_t findISOIndex(float pISO,uint8_t pMethod) //find index of closest iso from given iso table (pMethod)
{
  float _minDistance=abs(pISO-isoFull[0]);
  float _lastminDistance=_minDistance;
  uint8_t _index=0;

  
  while (_lastminDistance>=_minDistance) //until distance increases
  {
    _lastminDistance=_minDistance;
    
    switch(pMethod){
    case 1:
        _minDistance=abs(pISO - isoFull[_index]);
      break;
    case 2:
        _minDistance=abs(pISO - isoThird[_index]);
      break;
    }
    _index++; //next
  }
  return _index-2;
}

void updateDisplay()
{
  switch(displaymode){
    case lightmeter:
      updateDisplay_Lightmeter();
      break;
    case settings:
      updateDisplay_Settings();
      break;
  }

  
  display.display();
}

void updateDisplay_Lightmeter() //Lightmeter display
{
  #define xpos_aperature 2
  #define ypos_aperature 29
  #define xpos_shutter 60
  #define ypos_shutter 29

  #define xpos_debug 0
  #define ypos_debug 63-7

  #define xpos_iso 2
  #define ypos_iso 63-7-9
  
  display.clearDisplay();
  display.setTextColor(WHITE);
  
  //Aperature
  float _showAperature=roundAperature(showAperature,userSettings.aperatureSelectionMode);
  display.setTextSize(1);
  display.setCursor(xpos_aperature,ypos_aperature); display.print("F");
  display.setTextSize(2);
  display.setCursor(display.getCursorX(),display.getCursorY()); display.print(int(_showAperature));
  if ( int( (_showAperature-int(_showAperature) )*10  )  !=0){ //has a decimal
    display.setTextSize(1);
    display.setCursor(display.getCursorX()-2,display.getCursorY()+7); display.print("."); display.setCursor(display.getCursorX()+1,display.getCursorY()-7);
    display.setTextSize(2);
    display.setCursor(display.getCursorX()-2,display.getCursorY());
    display.print( (int)round( (_showAperature-int(_showAperature) )*10));
  }
  //Aperature border
  if (setAperature>0){ //Aperature Priority Mode
    display.drawRect(xpos_aperature-2, ypos_aperature-2, 40, 18, WHITE);
  }
  
  
  //Shutter
  display.setCursor(xpos_shutter,ypos_shutter); 
  float _showShutter=roundShutter(showShutter,userSettings.shutterSelectionMode);
  //Serial.print("rounded Shutter from "); Serial.print(showShutter); Serial.print(" to "); Serial.println(_showShutter); //asdf
  if (_showShutter>=1) //check time
  { //show full seconds
    display.print(int(_showShutter));
    if (_showShutter-int(_showShutter)>0){ //has decimals
      display.setTextSize(1);
      display.setCursor(display.getCursorX()-2,display.getCursorY()+7); display.print("."); display.setCursor(display.getCursorX()+1,display.getCursorY()-7);
      display.setTextSize(2);
      display.setCursor(display.getCursorX()-2,display.getCursorY());
      display.print( (int)round( (_showShutter-int(_showShutter))*10)); //show one decimal
    }
    display.setTextSize(1); display.setCursor(display.getCursorX(),display.getCursorY()+7);
    display.print("s");
  }else{ //show fraction of a second
    display.setTextSize(1); display.print("1");
    display.drawLine(display.getCursorX()+1,display.getCursorY(), display.getCursorX()-1, display.getCursorY()+9, WHITE);
    display.setTextSize(2); display.setCursor(display.getCursorX()+2,display.getCursorY());
    int _frac_showShutter = (int) (   (1.0f/( (int)(_showShutter*1000000) ) )*1000000 );
    display.print(  _frac_showShutter );
    display.setTextSize(1); display.setCursor(display.getCursorX(),display.getCursorY()+7);
    display.print("s");
  }
  //Shutter border
  if (setShutter>0){ //Shutter Priority Mode
    display.drawRect(xpos_shutter-2, ypos_shutter-2, 40, 18, WHITE);
  }
  
  //ISO
  display.setCursor(xpos_iso,ypos_iso); display.setTextSize(1); display.print("ISO "); display.print(setISO);
  
  //DEBUG Message
  display.setTextSize(1);
  display.setCursor(xpos_debug,ypos_debug);
  display.print(vbat);
  display.print("V ");
  display.print("Ev=");
  display.print(ev);
  display.print(" |");
  display.print(incident);

  display.setTextSize(1);
  display.setCursor(10,10);
  display.print(meteringmode);
  
}

void updateDisplay_Settings()
{
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setTextSize(1);
  #define SETTINGS_YPOS_INCREMENT 9
  #define SETTINGS_XPOS_OFFSET 1

  
  
  display.setCursor(SETTINGS_XPOS_OFFSET,0); //absolute position for first item

  for (uint8_t _currentItemIndex=0;_currentItemIndex<=SETTINGS_SELECTEDITEM_MAX;_currentItemIndex++)
  {
    if (settings_selectedItem==_currentItemIndex){
      if (settings_itemActive){
        display.drawRect(0, display.getCursorY()-2, 126 , 11, WHITE);
      }else{
        display.fillCircle(2, display.getCursorY()+3,2, WHITE); //x,y,r,color
      }
      display.setCursor(display.getCursorX()+5,display.getCursorY()); //move text to the right
    }
    display.print(settingStrings[_currentItemIndex]); 
    switch(_currentItemIndex){ //if values need to be shown
      case 0: display.print(setISO);
        break;
      case 1: display.print(settingsnameAperatureSelectionMode[userSettings.aperatureSelectionMode-1]);
        break;
      case 2: display.print(settingsnameShutterSelectionMode[userSettings.shutterSelectionMode-1]);
        break;
    }
  
    display.setCursor(SETTINGS_XPOS_OFFSET,display.getCursorY()+SETTINGS_YPOS_INCREMENT); //move cursor to next entry
  }



  /*
  if (settings_selectedItem==1){
    if (settings_itemActive){
      display.drawRect(display.getCursorX()-2, display.getCursorY()-2, 126 , 11, WHITE);
    }else{
      display.drawCircle(0, display.getCursorY()+4,2, display.getCursorY()+6);
    }
  }
  display.print("TestTest");*/

}