Pfthb

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.