ATSAMD10 - ASF - I2C im Slave Callback Mode läuft nicht

#include <asf.h>

#define DATA_LENGTH 2

#define SLAVE_ADDRESS 0x59

static uint8_t write_buffer[DATA_LENGTH] = { 0x00, 0x01 };

static uint8_t read_buffer [DATA_LENGTH];

struct i2c_slave_module i2c_slave_instance;

static struct i2c_slave_packet packet;

void configure_i2c_slave(void);

void i2c_read_request_callback(struct i2c_slave_module *const module);

void i2c_write_request_callback(struct i2c_slave_module *const module);

void configure_i2c_slave_callbacks(void);

int main (void)

{

  system_init();

  configure_i2c_slave();

  configure_i2c_slave_callbacks();

  while(1) {

    ;

  }

}

void configure_i2c_slave(void)

{

  /* Initialize config structure and module instance */

  struct i2c_slave_config config_i2c_slave;

  i2c_slave_get_config_defaults(&config_i2c_slave);

  /* Change address and address_mode */

  config_i2c_slave.address = SLAVE_ADDRESS;

  config_i2c_slave.address_mode = I2C_SLAVE_ADDRESS_MODE_MASK;

  /* Initialize and enable device with config */

  i2c_slave_init(&i2c_slave_instance, SERCOM2, &config_i2c_slave);

  i2c_slave_enable(&i2c_slave_instance);

  struct system_pinmux_config config_pinmux;

  system_pinmux_get_config_defaults(&config_pinmux);

  config_pinmux.mux_position = PINMUX_PA14D_SERCOM2_PAD0;

  system_pinmux_pin_set_config(PIN_PA14, &config_pinmux);

  system_pinmux_get_config_defaults(&config_pinmux);

  config_pinmux.mux_position = PINMUX_PA15D_SERCOM2_PAD1;

  system_pinmux_pin_set_config(PIN_PA15, &config_pinmux);

}

void i2c_read_request_callback(struct i2c_slave_module *const module)

{

  /* Init i2c packet */

  packet.data_length = DATA_LENGTH;

  packet.data = write_buffer;

  /* Write buffer to master */

  i2c_slave_write_packet_job(module, &packet);

}

void i2c_write_request_callback(struct i2c_slave_module *const module)

{

  /* Init i2c packet */

  packet.data_length = DATA_LENGTH;

  packet.data = read_buffer;

  /* Read buffer from master */

  if (i2c_slave_read_packet_job(module, &packet) != STATUS_OK) {

  }

}

void configure_i2c_slave_callbacks(void)

{

  /* Register and enable callback functions */

  i2c_slave_register_callback(&i2c_slave_instance, i2c_read_request_callback, I2C_SLAVE_CALLBACK_READ_REQUEST);

  i2c_slave_enable_callback(&i2c_slave_instance, I2C_SLAVE_CALLBACK_READ_REQUEST);

  i2c_slave_register_callback(&i2c_slave_instance, i2c_write_request_callback, I2C_SLAVE_CALLBACK_WRITE_REQUEST);

  i2c_slave_enable_callback(&i2c_slave_instance, I2C_SLAVE_CALLBACK_WRITE_REQUEST);

}