Quick Start Guide for TC - Callback

In this use case, the TC will be used to generate a PWM signal, with a varying duty cycle.

Here the pulse width is increased each time the timer count matches the set compare value. The TC module will be set up as follows:

• GCLK generator 0 (GCLK main) clock source
• 16-bit resolution on the counter
• No prescaler
• Normal PWM wave generation
• GCLK reload action
• Don't run in standby
• No inversion of waveform output
• No capture enabled
• Count upward
• Don't perform one-shot operations
• No event input enabled
• No event action
• No event generation enabled
• Counter starts on 0

Quick Start

Prerequisites

There are no prerequisites for this use case.

Code

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

• SAM D21 Xplained Pro.

  
  #define PWM_MODULE      EXT1_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT1_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT1_PWM_0_MUX

• SAM D20 Xplained Pro.

  
  #define PWM_MODULE      EXT1_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT1_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT1_PWM_0_MUX

• SAM R21 Xplained Pro.

  
  #define PWM_MODULE      EXT1_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT1_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT1_PWM_0_MUX

• SAM D11 Xplained Pro.

  
  #define PWM_MODULE      EXT1_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT1_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT1_PWM_0_MUX

• SAM L21 Xplained Pro.

  
  #define PWM_MODULE      EXT2_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT2_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT2_PWM_0_MUX

• SAM L22 Xplained Pro.

  
  #define PWM_MODULE      EXT3_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT3_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT3_PWM_0_MUX

• SAM DA1 Xplained Pro.

  
  #define PWM_MODULE      EXT1_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT1_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT1_PWM_0_MUX

• SAM HA1G16A Xplained Pro.

  
  #define PWM_MODULE      EXT1_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT1_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT1_PWM_0_MUX

• SAM C21 Xplained Pro.

  
  #define PWM_MODULE      EXT1_PWM_MODULE
  
  #define PWM_OUT_PIN     EXT1_PWM_0_PIN
  
  #define PWM_OUT_MUX     EXT1_PWM_0_MUX

  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_change_duty_cycle(
          struct tc_module *const module_inst)
  {
      static uint16_t i = 0;
  
      i += 128;
      tc_set_compare_value(module_inst, TC_COMPARE_CAPTURE_CHANNEL_0, i + 1);
  }

  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_16BIT;
      config_tc.wave_generation = TC_WAVE_GENERATION_NORMAL_PWM;
      config_tc.counter_16_bit.compare_capture_channel[0] = 0xFFFF;
  
      config_tc.pwm_channel[0].enabled = true;
      config_tc.pwm_channel[0].pin_out = PWM_OUT_PIN;
      config_tc.pwm_channel[0].pin_mux = PWM_OUT_MUX;
  
      tc_init(&tc_instance, PWM_MODULE, &config_tc);
  
      tc_enable(&tc_instance);
  }
  
  void configure_tc_callbacks(void)
  {
      tc_register_callback(
              &tc_instance,
              tc_callback_to_change_duty_cycle,
              TC_CALLBACK_CC_CHANNEL0);
  
      tc_enable_callback(&tc_instance, TC_CALLBACK_CC_CHANNEL0);
  }

  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 counter width, wave generation mode, and the compare channel 0 value.

          config_tc.counter_size    = TC_COUNTER_SIZE_16BIT;
          config_tc.wave_generation = TC_WAVE_GENERATION_NORMAL_PWM;
          config_tc.counter_16_bit.compare_capture_channel[0] = 0xFFFF;

   4. Alter the TC settings to configure the PWM output on a physical device pin.

          config_tc.pwm_channel[0].enabled = true;
          config_tc.pwm_channel[0].pin_out = PWM_OUT_PIN;
          config_tc.pwm_channel[0].pin_mux = PWM_OUT_MUX;

   5. Configure the TC module with the desired settings.

          tc_init(&tc_instance, PWM_MODULE, &config_tc);

   6. Enable the TC module to start the timer and begin PWM signal generation.

          tc_enable(&tc_instance);

3. Configure the TC callbacks.
   1. Register the Compare Channel 0 Match callback functions with the driver.

          tc_register_callback(
                  &tc_instance,
                  tc_callback_to_change_duty_cycle,
                  TC_CALLBACK_CC_CHANNEL0);

   2. Enable the Compare Channel 0 Match callback so that it will be called by the driver when appropriate.

          tc_enable_callback(&tc_instance, TC_CALLBACK_CC_CHANNEL0);

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 PWM wave is generated via the TC module.

       while (true) {
       }