Quick Start Guide for SERCOM I2C Master - Basic

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

• Master mode
• 100KHz operation speed
• Not operational in standby
• 10000 packet timeout value
• 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 send, a sample buffer to read:

  #define DATA_LENGTH 10
  static uint8_t write_buffer[DATA_LENGTH] = {
          0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
  };
  
  static uint8_t read_buffer[DATA_LENGTH];

• Slave address to access:

  #define SLAVE_ADDRESS 0x12

• Number of times to try to send packet if it fails:

  #define TIMEOUT 1000

• Globally accessible module structure:

  struct i2c_master_module i2c_master_instance;

• Function for setting up the module:

  void configure_i2c_master(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 = 10000;
  #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. */
      i2c_master_init(&i2c_master_instance, CONF_I2C_MASTER_MODULE, &config_i2c_master);
  
      i2c_master_enable(&i2c_master_instance);
  }

• Add to user application main():

      /* Configure device and enable. */
      configure_i2c_master();
  
      /* Timeout counter. */
      uint16_t timeout = 0;
  
      /* Init i2c packet. */
      struct i2c_master_packet packet = {
          .address     = SLAVE_ADDRESS,
          .data_length = DATA_LENGTH,
          .data        = write_buffer,
          .ten_bit_address = false,
          .high_speed      = false,
          .hs_master_code  = 0x0,
      };

Workflow

1. Configure and enable module.

   void configure_i2c_master(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 = 10000;
   #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. */
       i2c_master_init(&i2c_master_instance, CONF_I2C_MASTER_MODULE, &config_i2c_master);
   
       i2c_master_enable(&i2c_master_instance);
   }

   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 = 10000;
      #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.

          i2c_master_init(&i2c_master_instance, CONF_I2C_MASTER_MODULE, &config_i2c_master);

   4. Enable the module.

          i2c_master_enable(&i2c_master_instance);

2. Create a variable to see when we should stop trying to send packet.

       uint16_t timeout = 0;

3. Create a packet to send.

       struct i2c_master_packet packet = {
           .address     = SLAVE_ADDRESS,
           .data_length = DATA_LENGTH,
           .data        = write_buffer,
           .ten_bit_address = false,
           .high_speed      = false,
           .hs_master_code  = 0x0,
       };

Implementation

Code

Add to user application main():

    /* Write buffer to slave until success. */
    while (i2c_master_write_packet_wait(&i2c_master_instance, &packet) !=
            STATUS_OK) {
        /* Increment timeout counter and check if timed out. */
        if (timeout++ == TIMEOUT) {
            break;
        }
    }

    /* Read from slave until success. */
    packet.data = read_buffer;
    while (i2c_master_read_packet_wait(&i2c_master_instance, &packet) !=
            STATUS_OK) {
        /* Increment timeout counter and check if timed out. */
        if (timeout++ == TIMEOUT) {
            break;
        }
    }

Workflow

1. Write packet to slave.

       while (i2c_master_write_packet_wait(&i2c_master_instance, &packet) !=
               STATUS_OK) {
           /* Increment timeout counter and check if timed out. */
           if (timeout++ == TIMEOUT) {
               break;
           }
       }

   The module will try to send the packet TIMEOUT number of times or until it is successfully sent.
2. Read packet from slave.

       packet.data = read_buffer;
       while (i2c_master_read_packet_wait(&i2c_master_instance, &packet) !=
               STATUS_OK) {
           /* Increment timeout counter and check if timed out. */
           if (timeout++ == TIMEOUT) {
               break;
           }
       }

   The module will try to read the packet TIMEOUT number of times or until it is successfully read.