Quick Start Guide for SERCOM I2C Master - Callback

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

• Master mode
• 100KHz operation speed
• Not operational in standby
• 65535 unknown bus state timeout value

Prerequisites

The device must be connected to an I²C slave.

Setup

Code

The following must be added to the user application:

A sample buffer to write from, a reversed buffer to write from and length of buffers.

#define DATA_LENGTH 8

static uint8_t wr_buffer[DATA_LENGTH] = {
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07
};

static uint8_t wr_buffer_reversed[DATA_LENGTH] = {
    0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01, 0x00
};

static uint8_t rd_buffer[DATA_LENGTH];

Address of slave:

#define SLAVE_ADDRESS 0x12

Globally accessible module structure:

struct i2c_master_module i2c_master_instance;

Globally accessible packet:

struct i2c_master_packet wr_packet;
struct i2c_master_packet rd_packet;

Function for setting up module:

void configure_i2c(void)
{
    /* Initialize config structure and software module */
    struct i2c_master_config config_i2c_master;
    i2c_master_get_config_defaults(&config_i2c_master);

    /* Change buffer timeout to something longer */
    config_i2c_master.buffer_timeout = 65535;
#if SAMR30
    config_i2c_master.pinmux_pad0    = CONF_MASTER_SDA_PINMUX;
    config_i2c_master.pinmux_pad1    = CONF_MASTER_SCK_PINMUX;
#endif

    /* Initialize and enable device with config */
    while(i2c_master_init(&i2c_master_instance, CONF_I2C_MASTER_MODULE, &config_i2c_master)     \
            != STATUS_OK);

    i2c_master_enable(&i2c_master_instance);
}

Callback function for write complete:

void i2c_write_complete_callback(
        struct i2c_master_module *const module)
{
    /* Initiate new packet read */
    i2c_master_read_packet_job(&i2c_master_instance,&rd_packet);
}

Function for setting up the callback functionality of the driver:

void configure_i2c_callbacks(void)
{
    /* Register callback function. */
    i2c_master_register_callback(&i2c_master_instance, i2c_write_complete_callback,
            I2C_MASTER_CALLBACK_WRITE_COMPLETE);
    i2c_master_enable_callback(&i2c_master_instance,
            I2C_MASTER_CALLBACK_WRITE_COMPLETE);
}

Add to user application main():

    /* Configure device and enable. */
    configure_i2c();
    /* Configure callbacks and enable. */
    configure_i2c_callbacks();

Workflow

1. Configure and enable module.

       configure_i2c();

   1. Create and initialize configuration structure.

          struct i2c_master_config config_i2c_master;
          i2c_master_get_config_defaults(&config_i2c_master);

   2. Change settings in the configuration.

          config_i2c_master.buffer_timeout = 65535;
      #if SAMR30
          config_i2c_master.pinmux_pad0    = CONF_MASTER_SDA_PINMUX;
          config_i2c_master.pinmux_pad1    = CONF_MASTER_SCK_PINMUX;
      #endif

   3. Initialize the module with the set configurations.

          while(i2c_master_init(&i2c_master_instance, CONF_I2C_MASTER_MODULE, &config_i2c_master)     \
                  != STATUS_OK);

   4. Enable the module.

          i2c_master_enable(&i2c_master_instance);

2. Configure callback functionality.

       configure_i2c_callbacks();

   1. Register write complete callback.

          i2c_master_register_callback(&i2c_master_instance, i2c_write_complete_callback,
                  I2C_MASTER_CALLBACK_WRITE_COMPLETE);

   2. Enable write complete callback.

          i2c_master_enable_callback(&i2c_master_instance,
                  I2C_MASTER_CALLBACK_WRITE_COMPLETE);

3. Create a packet to send to slave.

       wr_packet.address     = SLAVE_ADDRESS;
       wr_packet.data_length = DATA_LENGTH;
       wr_packet.data        = wr_buffer;

Implementation

Code

Add to user application main():

    while (true) {
        /* Infinite loop */
        if (!port_pin_get_input_level(BUTTON_0_PIN)) {
            while (!port_pin_get_input_level(BUTTON_0_PIN)) {
                /* Waiting for button steady */ 
            }
            /* Send every other packet with reversed data */
            if (wr_packet.data[0] == 0x00) {
                wr_packet.data = &wr_buffer_reversed[0];
            } else {
                wr_packet.data = &wr_buffer[0];
            }
            i2c_master_write_packet_job(&i2c_master_instance, &wr_packet);
        }
    }

Workflow

1. Write packet to slave.

       wr_packet.address     = SLAVE_ADDRESS;
       wr_packet.data_length = DATA_LENGTH;
       wr_packet.data        = wr_buffer;

2. Infinite while loop, while waiting for interaction with slave.

       while (true) {
           /* Infinite loop */
           if (!port_pin_get_input_level(BUTTON_0_PIN)) {
               while (!port_pin_get_input_level(BUTTON_0_PIN)) {
                   /* Waiting for button steady */ 
               }
               /* Send every other packet with reversed data */
               if (wr_packet.data[0] == 0x00) {
                   wr_packet.data = &wr_buffer_reversed[0];
               } else {
                   wr_packet.data = &wr_buffer[0];
               }
               i2c_master_write_packet_job(&i2c_master_instance, &wr_packet);
           }
       }

Callback

Each time a packet is sent, the callback function will be called.

Workflow

• Write complete callback:
  1. Send every other packet in reversed order.

                 if (wr_packet.data[0] == 0x00) {
                     wr_packet.data = &wr_buffer_reversed[0];
                 } else {
                     wr_packet.data = &wr_buffer[0];
                 }

  2. Write new packet to slave.

         wr_packet.address     = SLAVE_ADDRESS;
         wr_packet.data_length = DATA_LENGTH;
         wr_packet.data        = wr_buffer;