Quick Start Guide for TC - Timer

In this use case, the TC will be used as a timer to generate overflow and compare match callbacks.

In the callbacks the on-board LED is toggled.

The TC module will be set up as follows:

• GCLK generator 1 (GCLK 32K) clock source
• 16-bit resolution on the counter
• Prescaler is divided by 64
• GCLK reload action
• Count upward
• Don't run in standby
• No waveform outputs
• No capture enabled
• Don't perform one-shot operations
• No event input enabled
• No event action
• No event generation enabled
• Counter starts on 0
• Counter top set to 2000 (about 4s) and generate overflow callback
• Channel 0 is set to compare and match value 900 and generate callback
• Channel 1 is set to compare and match value 930 and generate callback

Quick Start

Prerequisites

For this use case, XOSC32K should be enabled and available through GCLK generator 1 clock source selection. Within Atmel Software Framework (ASF) it can be done through modifying conf_clocks.h. See System Clock Management Driver for more details about clock configuration.

Code

Add to the main application source file, before any functions, according to the kit used:

• SAM D20 Xplained Pro.

  #define CONF_TC_MODULE TC3

• SAM D21 Xplained Pro.

  #define CONF_TC_MODULE TC3

• SAM R21 Xplained Pro.

  #define CONF_TC_MODULE TC3

• SAM D11 Xplained Pro.

  #define CONF_TC_MODULE TC1

• SAM L21 Xplained Pro.

  #define CONF_TC_MODULE TC3

• SAM L22 Xplained Pro.

  #define CONF_TC_MODULE TC3

• SAM DA1 Xplained Pro.

  #define CONF_TC_MODULE TC3

• SAM HA1G16A Xplained Pro.

  #define CONF_TC_MODULE TC3

• SAM C21 Xplained Pro.

  #define CONF_TC_MODULE TC3

  Add to the main application source file, outside of any functions:

  struct tc_module tc_instance;

  Copy-paste the following callback function code to your user application:

  void tc_callback_to_toggle_led(
          struct tc_module *const module_inst)
  {
      port_pin_toggle_output_level(LED0_PIN);
  }

  Copy-paste the following setup code to your user application:

  void configure_tc(void)
  {
      struct tc_config config_tc;
      tc_get_config_defaults(&config_tc);
  
      config_tc.counter_size = TC_COUNTER_SIZE_8BIT;
      #if (SAMR30E)
      config_tc.clock_source = GCLK_GENERATOR_0;
      #else
      config_tc.clock_source = GCLK_GENERATOR_1;
      #endif
      config_tc.clock_prescaler = TC_CLOCK_PRESCALER_DIV1024;
      config_tc.counter_8_bit.period = 100;
      config_tc.counter_8_bit.compare_capture_channel[0] = 50;
      config_tc.counter_8_bit.compare_capture_channel[1] = 54;
  
      tc_init(&tc_instance, CONF_TC_MODULE, &config_tc);
  
      tc_enable(&tc_instance);
  }
  
  void configure_tc_callbacks(void)
  {
      tc_register_callback(&tc_instance, tc_callback_to_toggle_led,
              TC_CALLBACK_OVERFLOW);
      tc_register_callback(&tc_instance, tc_callback_to_toggle_led,
              TC_CALLBACK_CC_CHANNEL0);
      tc_register_callback(&tc_instance, tc_callback_to_toggle_led,
              TC_CALLBACK_CC_CHANNEL1);
  
      tc_enable_callback(&tc_instance, TC_CALLBACK_OVERFLOW);
      tc_enable_callback(&tc_instance, TC_CALLBACK_CC_CHANNEL0);
      tc_enable_callback(&tc_instance, TC_CALLBACK_CC_CHANNEL1);
  }

  Add to user application initialization (typically the start of main()):

      configure_tc();
      configure_tc_callbacks();

Workflow

1. Create a module software instance structure for the TC module to store the TC driver state while it is in use.

   struct tc_module tc_instance;

   Note

   This should never go out of scope as long as the module is in use. In most cases, this should be global.

2. Configure the TC module.
   1. Create a TC module configuration struct, which can be filled out to adjust the configuration of a physical TC peripheral.

          struct tc_config config_tc;

   2. Initialize the TC configuration struct with the module's default values.

          tc_get_config_defaults(&config_tc);

      Note

      This should always be performed before using the configuration struct to ensure that all values are initialized to known default settings.

   3. Alter the TC settings to configure the GCLK source, prescaler, period, and compare channel values.

          config_tc.counter_size = TC_COUNTER_SIZE_8BIT;
          #if (SAMR30E)
          config_tc.clock_source = GCLK_GENERATOR_0;
          #else
          config_tc.clock_source = GCLK_GENERATOR_1;
          #endif
          config_tc.clock_prescaler = TC_CLOCK_PRESCALER_DIV1024;
          config_tc.counter_8_bit.period = 100;
          config_tc.counter_8_bit.compare_capture_channel[0] = 50;
          config_tc.counter_8_bit.compare_capture_channel[1] = 54;

   4. Configure the TC module with the desired settings.

          tc_init(&tc_instance, CONF_TC_MODULE, &config_tc);

   5. Enable the TC module to start the timer.

          tc_enable(&tc_instance);

3. Configure the TC callbacks.
   1. Register the Overflow and Compare Channel Match callback functions with the driver.

          tc_register_callback(&tc_instance, tc_callback_to_toggle_led,
                  TC_CALLBACK_OVERFLOW);
          tc_register_callback(&tc_instance, tc_callback_to_toggle_led,
                  TC_CALLBACK_CC_CHANNEL0);
          tc_register_callback(&tc_instance, tc_callback_to_toggle_led,
                  TC_CALLBACK_CC_CHANNEL1);

   2. Enable the Overflow and Compare Channel Match callbacks so that it will be called by the driver when appropriate.

          tc_enable_callback(&tc_instance, TC_CALLBACK_OVERFLOW);
          tc_enable_callback(&tc_instance, TC_CALLBACK_CC_CHANNEL0);
          tc_enable_callback(&tc_instance, TC_CALLBACK_CC_CHANNEL1);

Use Case

Code

Copy-paste the following code to your user application:

    system_interrupt_enable_global();

    while (true) {
    }

Workflow

1. Enter an infinite loop while the timer is running.

       while (true) {
       }