Double decimals not preserved when writing to oled screen

[sorin_jay]

I need to display all digits of longitude, but my oled screen is only displaying 2 decimals

I am using a htcc-AB02S Heltec

longitude is part of a scruct

struct recieveData{
  double  latitude;
  double  longitude;
  double altitudeM;
  double signalQuality;
  int locationAge;
  double speedKmph;
  double courseDeg; 
  int satellitesConnected;
  int gps_year;
  int gps_day;
  int gps_month; 
  int gps_hour;
  int gps_minute;
  int gps_second;
  int gps_centisecond;
  bool valid;  
};
recieveData rGpsData;

and it stores a value -117.706266, but when I try to draw it on my oled screen display, it only shows two decimals. How do I print all of it?

lineString = "R long " + String(double(rGpsData.longitude));

full Reciever code (just the part about displaying is nessisary, the rest I know works and I know I'm getting values into long):

/*
  parse data coming in and assign it to rdata stuffs on every recieve cycle.
*/

#include "Arduino.h"
#include <Wire.h>

#include "LoRaWan_APP.h"
#include "GPS_Air530.h"
#include "HT_SSD1306Wire.h"

SSD1306Wire  screen(0x3c, 500000, SDA, SCL, GEOMETRY_128_64, GPIO10 ); // addr , freq , i2c group , resolution , rst

Air530Class Gps;

#ifndef LoraWan_RGB
#define LoraWan_RGB 0
#endif

#define RF_FREQUENCY                                915000000 // Hz

#define TX_OUTPUT_POWER                             14        // dBm

#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                                 50 // Define the payload size here

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

static RadioEvents_t RadioEvents;

int16_t txNumber;

int16_t rssi,rxSize;

struct recieveData{
  double  latitude;
  double  longitude;
  double altitudeM;
  double signalQuality;
  int locationAge;
  double speedKmph;
  double courseDeg; 
  int satellitesConnected;
  int gps_year;
  int gps_day;
  int gps_month; 
  int gps_hour;
  int gps_minute;
  int gps_second;
  int gps_centisecond;
  bool valid;  
  
  //year, day, month, hour, minute, second, centisecond, lat, lng, alt.meters, sats, hdop (quality), age, coursedeg, speedkmph    
};
recieveData rGpsData;

struct selfData{
  double  latitude;
  double  longitude;
  double altitudeM;
  double signalQuality;
  int locationAge;
  double speedKmph;
  double courseDeg; 
  int satellitesConnected;
  int gps_year;
  int gps_day;
  int gps_month; 
  int gps_hour;
  int gps_minute;
  int gps_second;
  int gps_centisecond;
  bool valid;  
};
selfData sGpsData;

uint32_t gpsTimer = 0;
uint32_t displayInformationTimer = 0;

int timer1000 = 1000;

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

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


void displayInformation();

void setup() {
    Serial.begin(115200);
    VextON();
    
    Gps.begin(9600);
    Gps.setmode(MODE_GPS);

    rssi=0;
	
	  RadioEvents.RxDone = OnRxDone;
    Radio.Init( &RadioEvents );
    Radio.SetChannel( RF_FREQUENCY );
	
	Radio.SetRxConfig( MODEM_LORA, LORA_BANDWIDTH, LORA_SPREADING_FACTOR,
                                   LORA_CODINGRATE, 0, LORA_PREAMBLE_LENGTH,
                                   LORA_SYMBOL_TIMEOUT, LORA_FIX_LENGTH_PAYLOAD_ON,
                                   0, true, 0, 0, LORA_IQ_INVERSION_ON, true );
   
  screen.init();
  screen.clear();
  screen.display(); 
  screen.setTextAlignment(TEXT_ALIGN_CENTER);
  screen.setFont(ArialMT_Plain_10);
  screen.drawString(screen.width()/2,screen.height()/2,"gps comms 2 RX");
  screen.display(); 
  delay(1000);
  screen.clear();
  Serial.println("into RX mode");

  }

void loop(){
	Radio.Rx( 0 );
  delay(500);
  Radio.IrqProcess( );
  displayInformation();
}

void OnRxDone( uint8_t *payload, uint16_t size, int16_t rssi, int8_t snr ){
    rssi=rssi;
    rxSize=size;
    memcpy(rxpacket, payload, size );
    rxpacket[size]='\0';
    //turnOnRGB(COLOR_RECEIVED,0);
    Radio.Sleep( );
    parseMessage(rxpacket,rxSize, rssi);  
}

void parseMessage(char rxPacket[], int16_t rxSize, int16_t rssi){
  Serial.printf("\r\nreceived packet \"%s\" with rssi %d , length %d\r\n",rxPacket,rssi,rxSize);
  int numCommas = 0;
  String tempMessage;
  String val;
  for(int i = 0; i <= rxSize; i++){
    val = String(rxPacket[i]);
    
    if(val == ","){
      switch(numCommas){
        case 0: 
          //int hour
          rGpsData.gps_hour = tempMessage.toInt();
          //Serial.print("CnC: "); Serial.print(numCommas);
          //Serial.print("C  tM: "); Serial.println(tempMessage);
          break;
        case 1:
          //int minute
          rGpsData.gps_minute = tempMessage.toInt();
          //Serial.print("CnC: "); Serial.print(numCommas);
          //Serial.print("C tM: "); Serial.println(tempMessage);
          break;
        case 2:
          //int second
          rGpsData.gps_second = tempMessage.toInt();
          //Serial.print("CnC: "); Serial.print(numCommas);
          //Serial.print("C tM: "); Serial.println(tempMessage);
          break;
        case 3: 
         //int sats
          rGpsData.satellitesConnected = tempMessage.toInt();
          Serial.print("rGpsData.satellitesConnected"); Serial.println(rGpsData.satellitesConnected);
          //Serial.print("CnC: "); Serial.print(numCommas);
          Serial.print("C tM: "); Serial.println(tempMessage);
          break;
        case 4:
          //float lat
          rGpsData.latitude = tempMessage.toDouble();
          Serial.print("rGpsData.latitude"); Serial.println(rGpsData.latitude, 7);
          //Serial.print("CnC: "); Serial.print(numCommas);
          Serial.print("C tM: "); Serial.println(tempMessage);
          break;
        case 5:
          //float long
          rGpsData.longitude = tempMessage.toDouble();
          Serial.print("rGpsData.longitude"); Serial.println(rGpsData.longitude, 7);
          //Serial.print("CnC: "); Serial.print(numCommas);
          Serial.print("C tM: "); Serial.println(tempMessage);
          break;
        case 6:
          //double altitudeM
          rGpsData.altitudeM = tempMessage.toDouble();
          Serial.print("rGpsData.altitude"); Serial.println(rGpsData.altitudeM, 7);
          //Serial.print("CnC: "); Serial.print(numCommas);
          Serial.print(" tM: "); Serial.println(tempMessage);
          break;
        case 7:
          //bool valid
          if(tempMessage == "1"){
            rGpsData.valid = true;
          }
          else if (tempMessage == "0"){
            rGpsData.valid = false;
          }
          //Serial.print("CnC: "); Serial.print(numCommas);
          //Serial.print("C tM: "); Serial.println(tempMessage);
          break;  
        case 8:
          Serial.println("8 commas");
              
          Serial.print("8 nC: "); Serial.print(numCommas);
          Serial.print("8 tM: "); Serial.println(tempMessage);
          break;  
      }
      
      //Serial.print(" == nC: "); Serial.print(numCommas);
      //Serial.print(" == tM: "); Serial.println(tempMessage);
      tempMessage = "";
      numCommas++;
    }
    else if(val == "|"){
      if(rxPacket[i-1] == '1'){
        rGpsData.valid = true;
      }
      else if (rxPacket[i-1] == '0'){
        rGpsData.valid = false;
      }
      Serial.print("Valid: "); Serial.println(rGpsData.valid);
      break;
    }
    else{
      tempMessage += val;
    } 
  }   
}

void displayInformation(){
  if(millis() - displayInformationTimer >= timer1000){
    updateSelfInfo();
    Serial.println("========================");
    
    String lineString;
    screen.clear();
    screen.setFont(ArialMT_Plain_10);
    screen.setTextAlignment(TEXT_ALIGN_LEFT);
  
  //recieved data
    if(rGpsData.valid == true){
      lineString = "R long " + String(double(rGpsData.longitude));// + "  d " + String(rGpsData.gps_day) + "/" + String(rGpsData.gps_month) + "/" + String(rGpsData.gps_year);
      screen.drawString(0, 0,lineString);
      Serial.println(lineString);
  
      lineString = " R lat " + String(double(rGpsData.latitude));// + " alt " + String(rGpsData.altitudeM) + "  t " + String(rGpsData.gps_hour) + ":" + String(rGpsData.gps_minute) + ":" + String(rGpsData.gps_second);
      screen.drawString(0, 16,lineString);
      Serial.println(lineString);
    }
    else if(rGpsData.valid == false){
      screen.setFont(ArialMT_Plain_16);
      screen.setTextAlignment(TEXT_ALIGN_CENTER);
      
      lineString = "Recieved INVALID";
      screen.drawString(0, 0,lineString);
      Serial.println(lineString);
    }
      
  //self data
    if(sGpsData.valid == true){
      lineString = "S long " + String(double(sGpsData.longitude));// + " d " + String(sGpsData.gps_day) + "/" + String(sGpsData.gps_month) + "/" + String(sGpsData.gps_year);
      screen.drawString(0, 32,lineString);
      Serial.println(lineString);
    
      lineString = "lat " + String(double(sGpsData.latitude));// + " alt " + String(sGpsData.altitudeM) + " t " + String(sGpsData.gps_hour) + ":" + String(sGpsData.gps_minute) + ":" + String(sGpsData.gps_second);
      screen.drawString(0, 48,lineString);
      Serial.println(lineString);     
      
    }
    else if(sGpsData.valid == false){
      screen.setFont(ArialMT_Plain_16);
      screen.setTextAlignment(TEXT_ALIGN_CENTER);
      
      lineString = "SELF INVALID";
      screen.drawString(0, 32,lineString);
      Serial.println(lineString);
    }
    screen.display();
    Serial.println("========================");
  }
}

void updateSelfInfo(){
  readGps();
   /*//DEBUG PRINTS FOR LOOP
  Serial.print("day: "); Serial.println(data.gps_day);
  Serial.print("month: ");Serial.println(data.gps_month);
  Serial.print("gps_year: "); Serial.println(data.gps_year);
  Serial.print("hour: "); Serial.println(data.gps_hour);
  Serial.print("gps_minute: "); Serial.println(data.gps_minute);
  Serial.print("gps_second: "); Serial.println(data.gps_second); 
  Serial.print("gps_centisecond: "); Serial.println(data.gps_centisecond);
  Serial.print("latitude: "); Serial.println(data.latitude);
  Serial.print("longitude: "); Serial.println(data.longitude);
  Serial.print("altitudeM: "); Serial.println(data.altitudeM);
  Serial.print("satellites: "); Serial.println(data.satellitesConnected;);
  Serial.print("signalQuality: "); Serial.println(data.signalQuality);
  Serial.print("locationAge: "); Serial.println(data.locationAge);
  Serial.print("courseDeg: "); Serial.println(data.courseDeg);
  Serial.print("speedKmph: "); Serial.println(data.speedKmph);
  Serial.println(">>>>>>>>>>>>>>>>>>....................");
  delay(1000);
  */
  
  if (Gps.date.isValid()){
    sGpsData.valid = true;
    sGpsData.gps_day = Gps.date.day();
    sGpsData.gps_month = Gps.date.month();
    sGpsData.gps_year = Gps.date.year();
  }
  else{
    sGpsData.valid = false;
    Serial.print("INVALID++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++");
  }
 
  if (Gps.time.isValid()){ 
    sGpsData.valid = true;
    sGpsData.gps_hour = Gps.time.hour();
    sGpsData.gps_minute = Gps.time.minute();
    sGpsData.gps_second = Gps.time.second(); 
    sGpsData.gps_centisecond = Gps.time.centisecond();
  }
  else{
    sGpsData.valid = false;
    Serial.print(" INVALID++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++");
  }
  sGpsData.latitude = Gps.location.lat();
  sGpsData.longitude = Gps.location.lng();
  sGpsData.altitudeM = Gps.altitude.meters();
  sGpsData.satellitesConnected = Gps.satellites.value();
  sGpsData.signalQuality = Gps.hdop.hdop();
  sGpsData.locationAge = Gps.location.age();
  sGpsData.courseDeg = Gps.course.deg();
  sGpsData.speedKmph = Gps.speed.kmph();
  // debug prints
  Serial.println("self+++++++++++++++++++++++++++++++++"); 
  Serial.print("LAT: ");
  Serial.println(sGpsData.latitude,6);
  Serial.print(", LON: ");
  Serial.println(sGpsData.longitude,6);
  Serial.print(", ALT: ");
  Serial.println(sGpsData.altitudeM);
  Serial.print("SATS: ");
  Serial.println(sGpsData.satellitesConnected);
  Serial.print(", HDOP: ");
  Serial.println(sGpsData.signalQuality);
  Serial.print(", AGE: ");
  Serial.println(sGpsData.locationAge);
  Serial.print(", COURSE: ");
  Serial.println(sGpsData.courseDeg);
  Serial.print(", SPEED: ");
  Serial.println(sGpsData.speedKmph);
  Serial.println("++++++++++++++++++++++++++++++");
  Serial.println("recieved:::::::::::::::::::::::::::::::"); 
  Serial.print("LAT: ");
  Serial.println(rGpsData.latitude,6);
  Serial.print(", LON: ");
  Serial.println(rGpsData.longitude,6);
  Serial.print(", ALT: ");
  Serial.println(rGpsData.altitudeM);
  Serial.print("SATS: ");
  Serial.println(rGpsData.satellitesConnected);
  Serial.print("valid: ");
  Serial.println(rGpsData.valid);
  Serial.println("recieved:::::::::::::::::::::");
}

/*
  double  latitude;
  double  longitude;
  double altitudeM;
  double signalQuality;
  int locationAge;
  double speedKmph;
  double courseDeg; 
  int satellitesConnected;
  int gps_year;
  int gps_day;
  int gps_month; 
  int gps_hour;
  int gps_minute;
  int gps_second;
  int gps_centisecond;
  bool valid;  
*/

void readGps(){
   
  if(millis() - gpsTimer > timer1000){
    while(Gps.available() > 0){

      Gps.encode(Gps.read());
    }
    gpsTimer = millis();
  }  
  
  if (millis() > 5000 && Gps.charsProcessed() < 10)
  {
    
    sGpsData.valid = false;
    Serial.println("No GPS detected: check wiring.");
    while(true);
  }
}

[sorin_jay]

for instance, when I hard coded latitude right before I printed, it still only had two decimals

[anon57585045]

 Serial.print("rGpsData.latitude"); Serial.println(rGpsData.latitude, 7);

Is it a typo somewhere? Because the first suggestion is often to specify the number of decimal digits, but you have already done that.

[sorin_jay]

yes sorry, in serial it works just fine - I had forgotten to add the 7 there.
The issue is with converting the double to a string. When I do the string(longitude), it shortens. Ie:

rGpsData.longitude = -117.706266;
      String testerString = String(rGpsData.longitude);
      Serial.println("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!TESTER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"); 
      Serial.println(rGpsData.longitude, 8);
      Serial.println(testerString);
      lineString = "R long " + String(rGpsData.longitude);// + "  d " + String(rGpsData.gps_day) + "/" + String(rGpsData.gps_month) + "/" + String(rGpsData.gps_year);
      screen.drawString(0, 0,lineString);
      Serial.println(lineString);

here, longitude has decimals. When I print regular serial, it works with all the decimals. When I print testerString, which is String(longitude), it only has 2

is there a way to make a string or some way to print it while keeping all the values?

[anon57585045]

@sorin_jay

Serial.println(testerString);

IDK but try
Serial.println(testerString.toDouble() );
untested

[sorin_jay]

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!TESTER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
-117.70626600 :regular, nothing changed
-117.71 : testerstring
-117.71 : testerstring to double

[anon57585045]

Seems to me there was a thread on this a few weeks ago. Try a search.

[jremington]

DO NOT CROSS POST. Convert string to double retaining 7 decimals

[sorin_jay]

sorry, I posted here first and then people answered a different question I had in another so I asked them and was going to close this with the solution if they did.

[sorin_jay]

I'll move all the information from here to there.

Convert string to double retaining 7 decimals

Hi, I am a new programmer. I have a String called tempMessage which contains longitude and latitude, which are constantly changing. in my code, I do longitude = tempMessage.toDouble(); Say that tempMessage is 34.134408, longitude is only 34.13, if its -117.707238, it becomes 117.71, loosing the sign. How do I convert to preserve as many decimals as possible from the string to the double? If it is a char array using atof, then how do I record bytes one at a time, add to the char array, and …

this is the link to the other forum in case anyone is wondering where the answer is,

thank you jremington for reminding me:) I'm very new here