Quick Start Guide for SERCOM I2C Slave - Basic

In this use case, the I²C will used and set up as follows:

• Slave mode
• 100KHz operation speed
• Not operational in standby
• 10000 packet timeout value

Prerequisites

The device must be connected to an I²C master.

Setup

Code

The following must be added to the user application:

A sample buffer to write from, a sample buffer to read to and length of buffers:

#define DATA_LENGTH 10

uint8_t write_buffer[DATA_LENGTH] = {
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09
};
uint8_t read_buffer[DATA_LENGTH];

Address to respond to:

#define SLAVE_ADDRESS 0x12

Globally accessible module structure:

struct i2c_slave_module i2c_slave_instance;

Function for setting up the module:

void configure_i2c_slave(void)
{
    /* Create and initialize config_i2c_slave structure */
    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;
#if SAMR30  
    config_i2c_slave.pinmux_pad0    = CONF_SLAVE_SDA_PINMUX;
    config_i2c_slave.pinmux_pad1    = CONF_SLAVE_SCK_PINMUX;
#endif
    config_i2c_slave.buffer_timeout = 1000;

    /* Initialize and enable device with config_i2c_slave */
    i2c_slave_init(&i2c_slave_instance, CONF_I2C_SLAVE_MODULE, &config_i2c_slave);

    i2c_slave_enable(&i2c_slave_instance);
}

Add to user application main():

    configure_i2c_slave();

    enum i2c_slave_direction dir;
    struct i2c_slave_packet packet = {
        .data_length = DATA_LENGTH,
        .data        = write_buffer,
    };

Workflow

1. Configure and enable module.

       configure_i2c_slave();

   1. Create and initialize configuration structure.

          struct i2c_slave_config config_i2c_slave;
          i2c_slave_get_config_defaults(&config_i2c_slave);

   2. Change address and address mode settings in the configuration.

          config_i2c_slave.address        = SLAVE_ADDRESS;
          config_i2c_slave.address_mode   = I2C_SLAVE_ADDRESS_MODE_MASK;
      #if SAMR30  
          config_i2c_slave.pinmux_pad0    = CONF_SLAVE_SDA_PINMUX;
          config_i2c_slave.pinmux_pad1    = CONF_SLAVE_SCK_PINMUX;
      #endif
          config_i2c_slave.buffer_timeout = 1000;

   3. Initialize the module with the set configurations.

          i2c_slave_init(&i2c_slave_instance, CONF_I2C_SLAVE_MODULE, &config_i2c_slave);

   4. Enable the module.

          i2c_slave_enable(&i2c_slave_instance);

2. Create variable to hold transfer direction.

       enum i2c_slave_direction dir;

3. Create packet variable to transfer.

       struct i2c_slave_packet packet = {
           .data_length = DATA_LENGTH,
           .data        = write_buffer,
       };

Implementation

Code

Add to user application main():

    while (true) {
        /* Wait for direction from master */
        dir = i2c_slave_get_direction_wait(&i2c_slave_instance);

        /* Transfer packet in direction requested by master */
        if (dir == I2C_SLAVE_DIRECTION_READ) {
            packet.data = read_buffer;
            i2c_slave_read_packet_wait(&i2c_slave_instance, &packet);
        } else if (dir == I2C_SLAVE_DIRECTION_WRITE) {
            packet.data = write_buffer;
            i2c_slave_write_packet_wait(&i2c_slave_instance, &packet);
        }
    }

Workflow

1. Wait for start condition from master and get transfer direction.

           dir = i2c_slave_get_direction_wait(&i2c_slave_instance);

2. Depending on transfer direction, set up buffer to read to or write from, and write or read from master.

           if (dir == I2C_SLAVE_DIRECTION_READ) {
               packet.data = read_buffer;
               i2c_slave_read_packet_wait(&i2c_slave_instance, &packet);
           } else if (dir == I2C_SLAVE_DIRECTION_WRITE) {
               packet.data = write_buffer;
               i2c_slave_write_packet_wait(&i2c_slave_instance, &packet);
           }