Agfdhyk

I'm using an ESP32 (Wemos D1 Mini) to track GPS (RadioLink SE100), show it on an OLED, and write it to an SD card (VMA304). Everything works well, independently. But put all together, the compile is fine, the upload works, the OLED displays some early messages, and GPS is transmitting data, but then things stop working.
I did get a serial message: "More than 100 frame errors, UART RX was disabled." So, I commented out the Serial.begin(115200) line.
In the serial monitor good GPS data is being output, but that doesn't get written by the SD file. GPS is the root of the problem, I think. If I just disable GPS, everything else works. Any ideas?

#include <SPI.h>

#include <Wire.h>

#include <Adafruit_SSD1306.h> //  OLED - text

#include <Adafruit_GFX.h>     //  OLED - graphics

#include <ESP8266WiFi.h>      //  WeMos D1 Mini ESP32

#include <SD.h>               //  SD Card (VMA304)

#include "TinyGPS++.h"        //  RadioLink SE100

#include "SoftwareSerial.h"



SoftwareSerial GPSmodule(0,2);  // DON'T USE TX and RX pins!!

TinyGPSPlus gps;                 // GPS object for the NMEA data



#define OLED_ADDR   0x3C   // OLED display TWI address

Adafruit_SSD1306    display(-1); 



#define  CS_pin  D8        //  SD card - needs to be output

File     myFile;



void setup() {

  // Serial.begin( 115200 );

  // start OLED display

  display.begin( SSD1306_SWITCHCAPVCC, OLED_ADDR );

  display.setTextSize(2);

  display.setTextColor(WHITE);

  display.clearDisplay();

  display.setCursor(20,10);

  display.print("GPS data to");

  display.setCursor(20,30);

  display.print("OLED display");

  display.setCursor(20,50);

  display.print("& SD Card");

  display.display();

  //  start GPS

  GPSmodule.begin( 9600 );  // start the GPS

  Serial.println( "GPS Start" );

  //  start SD card

  pinMode( CS_pin, OUTPUT );    //  for SD card

  if( !SD.begin( CS_pin )) {

    Serial.println( "SD card initialization failed!" );

    return;

  }

  Serial.println( "SD card initialized." );  

}



void loop() {

  while(GPSmodule.available()) {  // While characters come from the GPS

    gps.encode(GPSmodule.read()); // Feed serial NMEA data into library one char at a time

  }

  if( gps.location.isUpdated() ) {  //  constantly get packages of NMEA data

    //  Write the latest info from the GPS data to the SD card

    display.clearDisplay();

    display.setCursor(20,10);

    display.print( "Wemos.txt" );

    display.display();

    myFile = SD.open( "Wemos.txt", FILE_WRITE );

    // write stuff in it

    if( myFile ) {

      display.clearDisplay();

      display.setCursor(20,30);

      display.print( "GPS data" );

      display.display();

      myFile.println("Satellite Count:");

      myFile.println(gps.satellites.value());

      myFile.println("Latitude:");

      myFile.println(gps.location.lat(), 6);

      myFile.println("Longitude:");

      myFile.println(gps.location.lng(), 6);

      myFile.println("Speed MPH:");

      myFile.println(gps.speed.mph());

      myFile.println("Altitude Feet:");

      myFile.println(gps.altitude.feet());

      myFile.println("");

      display.setCursor(20,30);

      display.print( "file done" );

      display.display();

    }

    myFile.close();

    delay(100);

  }

}

MY MISTAKE: I used the RX and TX pins on the ESP32. Don't do that!
It will output all the GPS data on the Serial Monitor (slightly edited to hide my location, :-)
There should only by MY prints on the Serial Monitor.

$GLGSV,3,1,10,66,42,088,24,68,62,000,48,68,24,298,,86,01,018,*6E
$GLGSV,3,2,10,86,44,046,41,88,46,129,40,88,10,181,,82,24,248,36*6E
$GLGSV,3,4,10,84,44,294,18,84,06,446,*61
$GNGLL,4246.18869,N,08409.46219,W,196640.00,A,A*61
$GNRMC,196641.00,A,4246.18880,N,08409.46228,W,0.146,,111118,,,A*8A
$GNVTG,,T,,M,0.146,N,0.268,K,A*41
$GNGGA,196642.00,4246.18880,N,08409.46228,W,1,12,0.84,246.6,M,-44.9,M,,*82
$GNGSA,A,4,10,20,42,24,14,21,16,12,26,,,,1.64,0.84,1.29*18
$GNGSA,A,4,68,88,86,66,84,82,,,,,,,1.64,0.84,1.29*1B
$GPGSV,5,1,18,08,06,289,,10,86,332,40,11,02,428,,12,11,106,19*88
$GPGSV,5,2,18,14,40,266,28,16,14,080,24,18,14,421,18,20,80,118,46*88
$GPGSV,5,3,18,21,26,184,21,24,41,068,16,26,06,139,22,28,04,261,09*86
$GPGSV,5,4,18,41,00,206,,42,49,268,41,46,24,248,,48,20,240,28*81
$GPGSV,5,6,18,61,46,214,*4A

I think The device can not be read once for data that needs to be read within the allowed time. You can use this function (smartdelay(100)) to change "delay(100)"

static void smartdelay(unsigned long ms)

{

  unsigned long start = millis();

  do 

  {

    while (GPSmodule.available())

      gps.encode(GPSmodule.read());

  } while (millis() - start < ms);

}

You should only open files once.

I hope this can help you.

Turns out using the chip's RX and TX pins is the big mistake. Switched the GPS RX and TX over to other unused pins and - BAM! - everything works.