Quick Start Guide for TC - Match Frequency Wave Generation

In this use case, the TC will be used to generate a match frequency.

The TC module will be set up as follows:

• GCLK generator 0 (GCLK main) clock source
• 16-bit resolution on the counter
• No prescaler
• Match frequency 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
• Capture compare channel 0 set to 4000

When system clock is 8MHz, and the compare channel 0 is 4000, the output frequency will be about 1KHz ( 8000000/4000/2 ).

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

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

  struct tc_module tc_instance;

  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_MATCH_FREQ;
      config_tc.counter_16_bit.compare_capture_channel[0] = 4000;
  
      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);
  }

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

      configure_tc();

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_MATCH_FREQ;
          config_tc.counter_16_bit.compare_capture_channel[0] = 4000;

   4. Alter the TC settings to configure the match frequency 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 match frequency wave generation.

          tc_enable(&tc_instance);

Use Case

Code

Copy-paste the following code to your user application:

    while (true) {
        /* Infinite loop */
    }

Workflow

1. Enter an infinite loop while the match frequency wave is generated via the TC module.

       while (true) {
           /* Infinite loop */
       }