With this setup it works

  Wire.begin(26, 32);  // (sda, sck)
  M5.begin(true, false, true);
  Serial.begin(115200);

#include <M5Atom.h>
#include <M5UnitScroll.h>

M5UnitScroll unitScroll;

void setup() {
  M5.begin();
  Serial.begin(115200);

  if (!unitScroll.begin()) {
  // if (!unitScroll.begin(&Wire, 0x40, 26, 32, 400000U)) {
  // if (!unitScroll.begin(&Wire, 0x40, 32, 26, 400000U)) {
    Serial.println("Errore nell'inizializzazione del sensore");
    while (1);  // Ferma il programma in caso di errore
  }

  // LED
  unitScroll.setLEDColor(0x0000FF);
}

void loop() {
  int32_t encoderValue = unitScroll.getEncoderValue();
  Serial.print("Valore encoder: ");
  Serial.println(encoderValue);

  if (unitScroll.getButtonStatus()) {
    Serial.println("Pulsante premuto!");
    unitScroll.setLEDColor(0xFF0000);  // Rosso
    delay(500);
    unitScroll.setLEDColor(0x00FF00);  // Verde
    delay(500);
  }

  delay(100);
}

but I need to connect the unit to the Atom grove port.... some tips??

#include <Wire.h>

void setup()
{
  Wire.begin(26, 32);  
  
  Serial.begin(115200);
  while (!Serial);             // Leonardo: wait for serial monitor
  Serial.println("\nI2C Scanner");
}

void loop()
{
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for(address = 1; address < 127; address++ ) 
  {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0)
    {
      Serial.print("I2C device found at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.print(address,HEX);
      Serial.println("  !");

      nDevices++;
    }
    else if (error==4) 
    {
      Serial.print("Unknown error at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.println(address,HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000);           // wait 5 seconds for next scan
}

and I can see 0x40

next I tried to put in two tab the modified library M5UnitScroll.h (for scl end sda atom pin) and M5UnitScroll.cpp..

M5UnitScroll.h

/*
 * SPDX-FileCopyrightText: 2024 M5Stack Technology CO LTD
 *
 * SPDX-License-Identifier: MIT
 */
#ifndef _M5UNITSCROLL_H_
#define _M5UNITSCROLL_H_

#include "Arduino.h"
#include "Wire.h"
#include "pins_arduino.h"

#define SCROLL_ADDR            0x40
#define ENCODER_REG             0x10
#define BUTTON_REG             0x20
#define RGB_LED_REG            0x30
#define RESET_REG              0x40
#define INC_ENCODER_REG         0x50
#define BOOTLOADER_VERSION_REG 0xFC
#define JUMP_TO_BOOTLOADER_REG 0xFD
#define FIRMWARE_VERSION_REG   0xFE
#define I2C_ADDRESS_REG        0xFF

class M5UnitScroll {
   private:
    uint8_t _addr;
    TwoWire* _wire;
    uint8_t _scl;
    uint8_t _sda;
    uint32_t _speed;
    void writeBytes(uint8_t addr, uint8_t reg, uint8_t* buffer, uint8_t length);
    void readBytes(uint8_t addr, uint8_t reg, uint8_t* buffer, uint8_t length);

   public:
    bool begin(TwoWire* wire = &Wire, uint8_t addr = SCROLL_ADDR, uint8_t sda = 26, uint8_t scl = 32, uint32_t speed = 400000U);
    int32_t getEncoderValue(void);
    int32_t getIncEncoderValue(void);
    bool getButtonStatus(void);
    void setLEDColor(uint32_t color, uint8_t index = 0);
    uint32_t getLEDColor(void);
    void setEncoderValue(int32_t encoder);
    void resetEncoder(void);
    bool getDevStatus(void);
    uint8_t getBootloaderVersion(void);
    uint8_t getFirmwareVersion(void);
    uint8_t setI2CAddress(uint8_t addr);
    uint8_t getI2CAddress(void);
    void jumpBootloader(void);
};

#endif

and M5UnitScroll.cpp

/*
 * SPDX-FileCopyrightText: 2024 M5Stack Technology CO LTD
 *
 * SPDX-License-Identifier: MIT
 */
#include "M5UnitScroll.h"

/*! @brief Initialize the Encoder. */
bool M5UnitScroll::begin(TwoWire *wire, uint8_t addr, uint8_t sda, uint8_t scl, uint32_t speed) {
    _wire  = wire;
    _addr  = addr;
    _sda   = sda;
    _scl   = scl;
    _speed = speed;
    _wire->begin(_sda, _scl);
    _wire->setClock(_speed);
    delay(10);
    _wire->beginTransmission(_addr);
    uint8_t error = _wire->endTransmission();
    if (error == 0) {
        return true;
    } else {
        return false;
    }
}

/*! @brief Write a certain length of data to the specified register address. */
void M5UnitScroll::writeBytes(uint8_t addr, uint8_t reg, uint8_t *buffer, uint8_t length) {
    _wire->beginTransmission(addr);
    _wire->write(reg);
    for (int i = 0; i < length; i++) {
        _wire->write(*(buffer + i));
    }
    _wire->endTransmission();
}

/*! @brief Read a certain length of data to the specified register address. */
void M5UnitScroll::readBytes(uint8_t addr, uint8_t reg, uint8_t *buffer, uint8_t length) {
    uint8_t index = 0;
    _wire->beginTransmission(addr);
    _wire->write(reg);
    _wire->endTransmission(false);
    _wire->requestFrom(addr, length);
    for (int i = 0; i < length; i++) {
        buffer[index++] = _wire->read();
    }
}

/*! @brief Read the encoder value.
    @return The value of the encoder that was read */
int32_t M5UnitScroll::getEncoderValue(void) {
    int32_t value = 0;

    readBytes(_addr, ENCODER_REG, (uint8_t *)&value, 4);
    return value;
}

/*! @brief Read the encoder inc value.
    @return The value of the encoder that was read */
int32_t M5UnitScroll::getIncEncoderValue(void) {
    int32_t value = 0;

    readBytes(_addr, INC_ENCODER_REG, (uint8_t *)&value, 4);
    return value;
}

/*! @brief Get the current status of the rotary encoder button.
    @return true if the button was pressed, otherwise false. */
bool M5UnitScroll::getButtonStatus(void) {
    uint8_t data;
    readBytes(_addr, BUTTON_REG, &data, 1);
    return data == 0x00;
}

/*! @brief Set the color of the LED (HEX). */
void M5UnitScroll::setLEDColor(uint32_t color, uint8_t index) {
    uint8_t data[4];
    data[3] = color & 0xff;
    data[2] = (color >> 8) & 0xff;
    data[1] = (color >> 16) & 0xff;
    data[0] = index;
    writeBytes(_addr, RGB_LED_REG, data, 4);
}

/*! @brief Get the color of the LED (HEX).
    @return The value of the led that was read */
uint32_t M5UnitScroll::getLEDColor(void) {
    uint8_t data[4];
    uint32_t value = 0;

    readBytes(_addr, RGB_LED_REG, data, 4);
    value = (data[3] | (data[2] << 8) | (data[1] << 16));
    return value;
}

void M5UnitScroll::setEncoderValue(int32_t encoder) {
    writeBytes(_addr, ENCODER_REG, (uint8_t *)&encoder, 4);
}

void M5UnitScroll::resetEncoder(void) {
    uint8_t data = 1;
    writeBytes(_addr, 0x40, &data, 1);
}

/*! @brief Get the dev status.
    @return 1 if the dev working, otherwise 0.. */
bool M5UnitScroll::getDevStatus(void) {
    _wire->beginTransmission(_addr);
    if (_wire->endTransmission() == 0)
        return true;
    else
        return false;
}

uint8_t M5UnitScroll::getBootloaderVersion(void) {
    _wire->beginTransmission(_addr);
    _wire->write(BOOTLOADER_VERSION_REG);
    _wire->endTransmission(false);

    uint8_t RegValue;

    _wire->requestFrom(_addr, 1);
    RegValue = _wire->read();
    return RegValue;
}

uint8_t M5UnitScroll::getFirmwareVersion(void) {
    _wire->beginTransmission(_addr);
    _wire->write(FIRMWARE_VERSION_REG);
    _wire->endTransmission(false);

    uint8_t RegValue;

    _wire->requestFrom(_addr, 1);
    RegValue = _wire->read();
    return RegValue;
}

uint8_t M5UnitScroll::setI2CAddress(uint8_t addr) {
    uint8_t temp[2] = {0};

    temp[0] = I2C_ADDRESS_REG;

    _wire->beginTransmission(_addr);
    _wire->write(temp[0]);
    _wire->write(addr);
    _wire->endTransmission();
    _addr = addr;
    return _addr;
}

uint8_t M5UnitScroll::getI2CAddress(void) {
    uint8_t temp[2] = {0};

    temp[0] = I2C_ADDRESS_REG;

    _wire->beginTransmission(_addr);
    _wire->write(temp[0]);
    _wire->endTransmission(false);

    uint8_t RegValue;

    _wire->requestFrom(_addr, 1);
    RegValue = _wire->read();
    return RegValue;
}

void M5UnitScroll::jumpBootloader(void) {
    uint8_t value = 1;

    writeBytes(_addr, JUMP_TO_BOOTLOADER_REG, (uint8_t *)&value, 1);
}

but this code outputs "error"

#include <M5Atom.h>
#include <Wire.h>
#include "M5UnitScroll.h"
// #include <M5UnitScroll.h>

M5UnitScroll unitScroll;

void setup() {
  M5.begin();

  Serial.begin(115200);
  Wire.begin(26, 32);  

  if (!unitScroll.begin()) {
    Serial.println("Error");
    while (1);
  }

  unitScroll.setLEDColor(0x0000FF);
}

void loop() {
  int32_t encoderValue = unitScroll.getEncoderValue();
  Serial.print("Valore encoder: ");
  Serial.println(encoderValue);

  if (unitScroll.getButtonStatus()) {
    Serial.println("Pulsante premuto!");
    unitScroll.setLEDColor(0xFF0000);  // Red
    delay(500);
    unitScroll.setLEDColor(0x00FF00);  // Green
    delay(500);
  }

  delay(100);  
}

#include <M5Atom.h>
#include "M5UnitScroll.h"

M5UnitScroll Scroll;

bool scrolla;

void setup() {
  M5.begin();
  Serial.begin(115200);
  Scroll.begin();
}

void loop() {
  scrolla = Scroll.begin();
  Serial.println(scrolla);
  delay(1000);
  scrolla = Scroll.begin(&Wire, SCROLL_ADDR, 32, 26);
  Serial.println(scrolla);
  delay(1000);
  scrolla = Scroll.begin(&Wire, SCROLL_ADDR, 26, 32);
  Serial.println(scrolla);
  delay(1000);
}

and the output in the serial monitor is:

10:56:20.024 -> 0
10:56:21.044 -> 0
10:56:22.062 -> 0
10:56:23.084 -> 0
10:56:24.071 -> 0
10:56:25.092 -> 0
10:56:26.081 -> 0
10:56:27.102 -> 0
10:56:28.129 -> 0

#include <M5Atom.h>
#include <M5UnitScroll.h>

M5UnitScroll Scroll;

int myVariable = 0;
int previousEncoderValue = 0;
bool buttonPressed = false;

void setup() {
  M5.begin();
  Serial.begin(115200);
  Scroll.begin(&Wire, 0x40, 26, 32);
}

void loop() {
  int currentEncoderValue = Scroll.getEncoderValue();
  int difference = currentEncoderValue - previousEncoderValue;
  myVariable += difference;
  previousEncoderValue = currentEncoderValue;

  if (Scroll.getButtonStatus()) {
    if (!buttonPressed) {
      myVariable = 0;
      buttonPressed = true;
    }
  } else {
    buttonPressed = false;
  }
  Serial.print("myVariable ");
  Serial.println(myVariable);
  Serial.print("buttonPressed ");
  Serial.println(buttonPressed);
}

some tips?