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esp_err_t I2C_MASTER_MODB_init(void)
{
    int i2c_master_port = I2C_MASTER_MODB_NUM;

    ESP_ERROR_CHECK(gpio_set_direction(I2C_MASTER_MODB_SCL_IO, GPIO_MODE_INPUT_OUTPUT_OD)); 
    ESP_ERROR_CHECK(gpio_set_direction(I2C_MASTER_MODB_SDA_IO, GPIO_MODE_INPUT_OUTPUT_OD));

    ESP_ERROR_CHECK(gpio_set_pull_mode(I2C_MASTER_MODB_SCL_IO, GPIO_PULLUP_ONLY));
    ESP_ERROR_CHECK(gpio_set_pull_mode(I2C_MASTER_MODB_SDA_IO, GPIO_PULLUP_ONLY));

    ESP_ERROR_CHECK(gpio_set_direction(I2C_MASTER_MODB_ADDCS_IO, GPIO_MODE_INPUT));
    ESP_ERROR_CHECK(gpio_set_pull_mode(I2C_MASTER_MODB_ADDCS_IO, GPIO_PULLUP_ONLY));

    i2c_config_t conf = {
        .mode = I2C_MODE_MASTER,
        .sda_io_num = I2C_MASTER_MODB_SDA_IO,
        .scl_io_num = I2C_MASTER_MODB_SCL_IO,
        .sda_pullup_en = GPIO_PULLUP_ENABLE,
        .scl_pullup_en = GPIO_PULLUP_ENABLE,
        .master.clk_speed = I2C_MASTER_FREQ_HZ,
    };

    i2c_param_config(i2c_master_port, &conf);

    // raised interrupt priority - TBD test
    return i2c_driver_install(i2c_master_port, conf.mode, I2C_MASTER_RX_BUF_DISABLE, I2C_MASTER_TX_BUF_DISABLE,  ESP_INTR_FLAG_LOWMED | ESP_INTR_FLAG_IRAM);
}

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unsigned char glob_i2c_iLastModbusReadSize = 0;
unsigned char arr_i2c_ucLastModbusReadBuf[256];
void IRAM_ATTR i2c_PIC24_UART485_read(unsigned char* getc, short size_getc, unsigned short* sI2CModbusResponse)
{
    i2c_port_t i2c_num = I2C_MASTER_MODB_NUM;
    unsigned char i2c_writecount_or_read = 2;
    
    unsigned short i2c_ResponseSize = 3;
    unsigned char i2c_writecount_buffer_response = size_getc + 2;

    unsigned char i2c_reg = I2C_REG_MODBUS_READ;
    unsigned short i2c_response = I2C_MODBUS_Negative_Acknowledge;

    if(((size_getc + i2c_ResponseSize) < 256) && (size_getc > 0) )
    {
        if(size_getc >= 9)
        {
            volatile short TBDBreakpoint = 5; // In diesem Fall Problem
            TBDBreakpoint = 6;
        }

        TaskHandle_t taskHandle = xGetCurrentTaskHandle();
        UBaseType_t taskPrior = uxTaskPriorityGet(taskHandle);

        vTaskDelay(20 / portTICK_PERIOD_MS);

        i2c_cmd_handle_t cmd = i2c_cmd_link_create();
        i2c_master_start(cmd);
        i2c_master_write_byte(cmd, (IO_EXP_BOARD_ADDR << 1) | WRITE_BIT, ACK_CHECK_EN);
        i2c_master_write_byte(cmd, i2c_writecount_or_read, ACK_CHECK_EN);
        i2c_master_write_byte(cmd, i2c_reg, ACK_CHECK_EN);
        i2c_master_write_byte(cmd, i2c_writecount_buffer_response, ACK_CHECK_EN);
        
        i2c_master_stop(cmd);

        esp_err_t ret = i2c_master_cmd_begin(i2c_num, cmd, 3000 / portTICK_PERIOD_MS);
        i2c_cmd_link_delete(cmd);
        if (ret != ESP_OK) {
            *sI2CModbusResponse = I2C_MODBUS_Negative_Acknowledge;

            vTaskDelay(100 / portTICK_PERIOD_MS);
            return;
        }

        vTaskDelay(30 / portTICK_PERIOD_MS);
        
        cmd = i2c_cmd_link_create();
        i2c_master_start(cmd);
        i2c_master_write_byte(cmd, (IO_EXP_BOARD_ADDR << 1) | READ_BIT, ACK_CHECK_EN);

        i2c_master_read_byte(cmd, (unsigned char*) &glob_i2c_iLastModbusReadSize, ACK_VAL);
        //i2c_master_read(cmd, (unsigned char*)&i2c_response, 2, ACK_VAL);

        i2c_master_read_byte(cmd,  (unsigned char*)&i2c_response, ACK_VAL);
        i2c_master_read_byte(cmd, (unsigned char*)(((unsigned char*)&i2c_response) +1), ACK_VAL);
        // anscheinend kann Read nur einmal pro command verwendet werden

       // size_getc verwenden
        if (size_getc > 1) {
            i2c_master_read(cmd, (unsigned char*)arr_i2c_ucLastModbusReadBuf, size_getc-1, ACK_VAL);
        }
        i2c_master_read_byte(cmd, &(((unsigned char*)arr_i2c_ucLastModbusReadBuf)[size_getc-1]), NACK_VAL);

        i2c_master_stop(cmd);

        ret = i2c_master_cmd_begin(i2c_num, cmd, 5000 / portTICK_PERIOD_MS);
        i2c_cmd_link_delete(cmd);

        vTaskDelay(50 / portTICK_PERIOD_MS);    // stattdessen pollen, könnte länger dauern... dynamische Zeit
        
        if (ret != ESP_OK) {
            *sI2CModbusResponse = I2C_MODBUS_Negative_Acknowledge;

            vTaskDelay(100 / portTICK_PERIOD_MS);
            return;
        }

        *sI2CModbusResponse = i2c_response;
        memcpy( getc, arr_i2c_ucLastModbusReadBuf, min(size_getc, glob_i2c_iLastModbusReadSize));


        vTaskDelay(10 / portTICK_PERIOD_MS);

        return;
    }
    else
    {
        // error overflow
        *sI2CModbusResponse = I2C_MODBUS_Negative_Acknowledge;
        return;
    }
}

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#define I2C_MASTER_FREQ_HZ          50000    // 100000        /*!< I2C master clock frequency */
#define I2C_MASTER_TX_BUF_DISABLE   0                          /*!< I2C master doesn't need buffer */
#define I2C_MASTER_RX_BUF_DISABLE   0                          /*!< I2C master doesn't need buffer */

#define I2C_MASTER_MODB_SCL_IO           16                          /*CONFIG_I2C_MASTER_SCL*/  /*!< GPIO number used for I2C master clock */
#define I2C_MASTER_MODB_SDA_IO           32                          /*CONFIG_I2C_MASTER_SDA*/  /*!< GPIO number used for I2C master data  */
#define I2C_MASTER_MODB_NUM              0                          /*!< I2C master i2c port number, the number of i2c peripheral interfaces available will depend on the chip */
#define I2C_MASTER_MODB_TIMEOUT_MS       1000

#define I2C_MASTER_MODB_ADDCS_IO           4                          /*!< GPIO number used for I2C additional CS  */

#define ESP_I2C_ADDR                         0x11         // Address of this ESP32
#define IO_EXP_BOARD_ADDR                    0x12         // Address of IO_EXP

#define REGISTER_IDENTIFICATION_ADDR          0x1         // Address of Identification Register 

#define REGISTER_PWR_MGMT_1_REG_ADDR          0xA         // Address of the power managment register
#define REGISTER_PWR_MGMT_1_RESET_BIT           7

#define WRITE_BIT       I2C_MASTER_WRITE                /*!< I2C master write */
#define READ_BIT        I2C_MASTER_READ                 /*!< I2C master read */

#define ACK_CHECK_EN    0x1                             /*!< I2C master will check ack from slave*/
#define ACK_CHECK_DIS   0x0                             /*!< I2C master will not check ack from slave */
#define ACK_VAL         0x0                             /*!< I2C ack value */
#define NACK_VAL        0x1                             /*!< I2C nack value */

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        i2c_master_write_byte(cmd, (IO_EXP_BOARD_ADDR << 1) | WRITE_BIT, ACK_CHECK_EN);
        i2c_master_write_byte(cmd, i2c_writecount_or_read, ACK_CHECK_EN);
        i2c_master_write_byte(cmd, i2c_reg, ACK_CHECK_EN);
        i2c_master_write_byte(cmd, i2c_writecount_buffer_response, ACK_CHECK_EN);

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const uint8_t data[4] = {(IO_EXP_BOARD_ADDR << 1) | WRITE_BIT, i2c_writecount_or_read, i2c_reg, i2c_writecount_buffer_response};
i2c_master_write(cmd, data, sizeof(data), ACK_CHECK_EN);