The M5StickCPlus2 has a weird behaviour in regards to the I2c bus.

Before my M5Stick arrived, I tested the M5Stack Mini Scale with my Esp32 (Doit Devkit 1) successfully with the following code.

#include <Arduino.h>
#include <M5Unified.h>
#include "UNIT_SCALES.h"

#include <WiFi.h>
#include <PubSubClient.h>

#include <InfluxDbClient.h>
#include <InfluxDbCloud.h>

#define millis_between_readings 500

// WiFi
const char* ssid = ".....";
const char* password = "....";

#if defined(ESP32)
  #include <WiFiMulti.h>
  WiFiMulti wifiMulti;
  #define DEVICE "ESP32"
#elif defined(ESP8266)
  #include <ESP8266WiFiMulti.h>
  ESP8266WiFiMulti wifiMulti;
  #define DEVICE "ESP8266"
#endif


#define INFLUXDB_URL "....."
#define INFLUXDB_TOKEN "....."
#define INFLUXDB_ORG "...."
#define INFLUXDB_BUCKET "...."
  
// Time zone info
#define TZ_INFO "UTC2"
  
// Declare InfluxDB client instance with preconfigured InfluxCloud certificate
InfluxDBClient client(INFLUXDB_URL, INFLUXDB_ORG, INFLUXDB_BUCKET, INFLUXDB_TOKEN, InfluxDbCloud2CACert);
  
// Declare Data point
Point sensorP("ESP32_1");

UNIT_SCALES scales;


void setup()
{

  M5.begin();
  
  // Setup wifi
  Serial.print("Connecting to WiFi: [");
  Serial.print(ssid);
  Serial.print("] password: [");
  Serial.print(password);
  Serial.print("]");
  Serial.println();
  Serial.print("Connecting to wifi");

  WiFi.mode(WIFI_STA);
  wifiMulti.addAP(ssid, password);

  WiFi.disconnect();
  delay(1);
  while (wifiMulti.run() != WL_CONNECTED) {
    Serial.println(WiFi.status());
    Serial.print(" ");
    delay(1000);
  }

  Serial.println("Connected to the Wi-Fi network");
    // Accurate time is necessary for certificate validation and writing in batches
  // We use the NTP servers in your area as provided by: https://www.pool.ntp.org/zone/
  // Syncing progress and the time will be printed to Serial.
  timeSync(TZ_INFO, "pool.ntp.org", "time.nis.gov");

    // Check server connection
  if (client.validateConnection()) {
    Serial.print("Connected to InfluxDB: ");
    Serial.println(client.getServerUrl());
  } else {
    Serial.print("InfluxDB connection failed: ");
    Serial.println(client.getLastErrorMessage());
  }

  sensorP.addTag("device", DEVICE);
  sensorP.addTag("sensorType", "HT711");

  
  while (!scales.begin(&Wire, 21, 22, DEVICE_DEFAULT_ADDR))
  {
    Serial.println("scales connect error");
    M5.Lcd.print("scales connect error");
    delay(1000);
  }
}

char *toCharArray(String str)
{
  return &str[0];
}

void loop()
{
  // Clear fields for reusing the point. Tags will remain the same as set above.
  sensorP.clearFields();


  
  // Delay between measurements.
  sensorP.addField("weight", scales.getWeight());
  sensorP.addField("gap",  scales.getGapValue());
  sensorP.addField("adc",  scales.getRawADC());
  // Write point
  if (!client.writePoint(sensorP)) {
    Serial.print("InfluxDB write failed: ");
    Serial.println(client.getLastErrorMessage());
  }
  
  Serial.println("Pausing till next reading");
  delay(millis_between_readings);
}

Here is a picture of the wiring I used to bridge the gap between the M5 connector and the Devkit 1. (Green: VIN, Gray: GND, Purple: D21, White D22).

Anyone any idea what these two boards work differently?

Greetings Pascal