My configuration is a Core2 stacked to a M5Stack GNSS Module, newly bought on M5Stack Store.

I don't manage to receive valid data from the GPS Module. The Serial stream and the source code are copied below.

Thank you in advance for your support,

Regards,
Philippe

``
--- Settings: /dev/cu.usbserial-57130480381 115200,8,N,1
--- RTS: active DTR: active BREAK: inactive
--- CTS: inactive DSR: inactive RI: inactive CD: inactive
--- software flow control: inactive
--- hardware flow control: inactive
--- serial input encoding: UTF-8
--- serial output encoding: UTF-8
--- EOL: CRLF
--- filters: default
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 9960 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 11392 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 12828 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 14268 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 15710 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 17152 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 18599 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 20048 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 21519 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 22972 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 24435 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 25906 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 27544 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 29184 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 30819 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 32460 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 34108 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 35775 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 37424 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 39081 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 40724 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 42372 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 44017 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 45657 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 47299 0 0
**** ***** 0.000000 *********** **** ********** ******** **** ****** ****** ***** *** ******** ****** *** 48941 0 0

The Code is below :

#include <M5Core2.h>
#include "M5Module_GNSS.h"
#include <TinyGPSPlus.h>
#include <Adafruit_BMP280.h>
#include <WiFiManager.h> // https://github.com/tzapu/WiFiManager
#include <SPI.h>
#include <WiFi.h>
#include <MQTT.h>


static void smartDelay(unsigned long ms);
static void printFloat(float val, bool valid, int len, int prec);
static void printInt(unsigned long val, bool valid, int len);
static void printDateTime(TinyGPSDate &d, TinyGPSTime &t);
static void printStr(const char *str, int len);

TinyGPSPlus gps;
static const double LONDON_LAT = 51.508131, LONDON_LON = -0.128002;


//Fonction pour MQTT
unsigned long lastMillis = 0;

void setup()
{
    //M5.begin(true, true, true, false, kMBusModeInput);  
    //M5.begin(); 
    M5.begin();
    
    Serial.begin(115200);
    while (!Serial)
        ;


    //Connexion du GPS
    Serial2.begin(115200, SERIAL_8N1, 13, 14);

    M5.Lcd.println();
    M5.Lcd.println(F(
        "Sats HDOP  Latitude   Longitude   Fix  Date       Time     Date Alt   "
        " Course Speed Card  Distance Course Card  Chars Sentences Checksum"));
    M5.Lcd.println(
        F("           (deg)      (deg)       Age                      Age  (m) "
          "   --- from GPS ----  ---- to London  ----  RX    RX        Fail"));
    M5.Lcd.println(F(
        "----------------------------------------------------------------------"
        "------------------------------------------------------------------"));
  
   

}

void loop()
{
  
    printInt(gps.satellites.value(), gps.satellites.isValid(), 5);
    printFloat(gps.hdop.hdop(), gps.hdop.isValid(), 6, 1);
    //printFloat(gps.location.lat(), gps.location.isValid(), 11, 6);
    printFloat(gps.location.lat(), true, 11, 6);

    printFloat(gps.location.lng(), gps.location.isValid(), 12, 6);
    printInt(gps.location.age(), gps.location.isValid(), 5);
    printDateTime(gps.date, gps.time);
    printFloat(gps.altitude.meters(), gps.altitude.isValid(), 7, 2);
    printFloat(gps.course.deg(), gps.course.isValid(), 7, 2);
    printFloat(gps.speed.kmph(), gps.speed.isValid(), 6, 2);
    printStr(
        gps.course.isValid() ? TinyGPSPlus::cardinal(gps.course.deg()) : "*** ",
        6);

    unsigned long distanceKmToLondon =
        (unsigned long)TinyGPSPlus::distanceBetween(
            gps.location.lat(), gps.location.lng(), LONDON_LAT, LONDON_LON) /
        1000;
    printInt(distanceKmToLondon, gps.location.isValid(), 9);

    double courseToLondon = TinyGPSPlus::courseTo(
        gps.location.lat(), gps.location.lng(), LONDON_LAT, LONDON_LON);

    printFloat(courseToLondon, gps.location.isValid(), 7, 2);

    const char *cardinalToLondon = TinyGPSPlus::cardinal(courseToLondon);

    printStr(gps.location.isValid() ? cardinalToLondon : "*** ", 6);

    printInt(gps.charsProcessed(), true, 6);
    printInt(gps.sentencesWithFix(), true, 10);
    printInt(gps.failedChecksum(), true, 9);
    Serial.println();

    smartDelay(1000);

    if (millis() > 5000 && gps.charsProcessed() < 10)
        Serial.println(F("No GPS data received: check wiring"));

    
        
}

// This custom version of delay() ensures that the gps object
// is being "fed".
static void smartDelay(unsigned long ms) {
    unsigned long start = millis();
    do {
        while (Serial2.available()) gps.encode(Serial2.read());
    } while (millis() - start < ms);
}

static void printFloat(float val, bool valid, int len, int prec) {
    if (!valid) {
        while (len-- > 1) Serial.print('*');
        Serial.print(' ');
    } else {
        Serial.print(val, prec);
        int vi   = abs((int)val);
        int flen = prec + (val < 0.0 ? 2 : 1);  // . and -
        flen += vi >= 1000 ? 4 : vi >= 100 ? 3 : vi >= 10 ? 2 : 1;
        for (int i = flen; i < len; ++i) Serial.print(' ');
    }
    smartDelay(0);
}

static void printInt(unsigned long val, bool valid, int len) {
    char sz[32] = "*****************";
    if (valid) sprintf(sz, "%ld", val);
    sz[len] = 0;
    for (int i = strlen(sz); i < len; ++i) sz[i] = ' ';
    if (len > 0) sz[len - 1] = ' ';
    Serial.print(sz);
    smartDelay(0);
}

static void printDateTime(TinyGPSDate &d, TinyGPSTime &t) {
    if (!d.isValid()) {
        Serial.print(F("********** "));
    } else {
        char sz[32];
        sprintf(sz, "%02d/%02d/%02d ", d.month(), d.day(), d.year());
        Serial.print(sz);
    }

    if (!t.isValid()) {
        Serial.print(F("******** "));
    } else {
        char sz[32];
        sprintf(sz, "%02d:%02d:%02d ", t.hour(), t.minute(), t.second());
        Serial.print(sz);
    }

    printInt(d.age(), d.isValid(), 5);
    smartDelay(0);
}

static void printStr(const char *str, int len) {
    int slen = strlen(str);
    for (int i = 0; i < len; ++i) Serial.print(i < slen ? str[i] : ' ');
    smartDelay(0);
}