Quick Start Guide for TCC - Double Buffering and Circular

The supported board list:

• SAM D21/R21/L21/L22/DA1/C21/HA1G16A Xplained Pro

In this use case, the TCC will be used to generate a PWM signal. Here the pulse width alters in one quarter and three quarter of the period. When the PWM signal connects to LED, LED will light. To see the waveform, you may need an oscilloscope. SAMHA1G16A Xpro LED is PA00 which isn't connected out, use PA04 instead, so we can't see LED blink but only see the waveform from oscilloscope.

The PWM output is set up as follows:

Board	Pin	Connect to
SAM D21 Xpro	PB30	LED0
SAM R21 Xpro	PA19	LED0
SAM L21 Xpro	PB10	LED0
SAM L22 Xpro	PC27	LED0
SAM DA1 Xpro	PB30	LED0
SAM C21 Xpro	PA15	LED0
SAM HA1G16A Xpro	PA04	NULL

The TCC module will be set up as follows:

• GCLK generator 0 (GCLK main) clock source
• Use double buffering write when set top, compare, or pattern through API
• No dithering on the counter or compare
• Prescaler is set to 1024
• Single Slope PWM wave generation
• GCLK reload action
• Don't run in standby
• No fault or waveform extensions
• 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
• Counter top set to 8000
• Capture compare channel set to 8000/4
• Capture compare channel buffer set to 8000*3/4
• Circular option for compare channel is enabled so that the compare values keep switching on update condition

Quick Start

Prerequisites

There are no prerequisites for this use case.

Code

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

#if SAMR30G

#define CONF_PWM_MODULE      LED_0_PWM3CTRL_MODULE

#define CONF_PWM_CHANNEL     LED_0_PWM3CTRL_CHANNEL

#define CONF_PWM_OUTPUT      LED_0_PWM3CTRL_OUTPUT

#define CONF_PWM_OUT_PIN     LED_0_PWM3CTRL_PIN

#define CONF_PWM_OUT_MUX     LED_0_PWM3CTRL_MUX

#elif SAMR30E

#define CONF_PWM_MODULE      LED_1_PWM2CTRL_MODULE

#define CONF_PWM_CHANNEL     LED_1_PWM2CTRL_CHANNEL

#define CONF_PWM_OUTPUT      LED_1_PWM2CTRL_OUTPUT

#define CONF_PWM_OUT_PIN     LED_1_PWM2CTRL_PIN

#define CONF_PWM_OUT_MUX     LED_1_PWM2CTRL_MUX

#else

#define CONF_PWM_MODULE      LED_0_PWM4CTRL_MODULE

#define CONF_PWM_CHANNEL     LED_0_PWM4CTRL_CHANNEL

#define CONF_PWM_OUTPUT      LED_0_PWM4CTRL_OUTPUT

#define CONF_PWM_OUT_PIN     LED_0_PWM4CTRL_PIN

#define CONF_PWM_OUT_MUX     LED_0_PWM4CTRL_MUX
#endif

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

struct tcc_module tcc_instance;

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

static void configure_tcc(void)
{
    struct tcc_config config_tcc;
    tcc_get_config_defaults(&config_tcc, CONF_PWM_MODULE);

    config_tcc.counter.clock_prescaler = TCC_CLOCK_PRESCALER_DIV1024;
    config_tcc.counter.period = 8000;
    config_tcc.compare.wave_generation = TCC_WAVE_GENERATION_SINGLE_SLOPE_PWM;
    config_tcc.compare.match[CONF_PWM_CHANNEL] = (8000 / 4);

    config_tcc.pins.enable_wave_out_pin[CONF_PWM_OUTPUT] = true;
    config_tcc.pins.wave_out_pin[CONF_PWM_OUTPUT]        = CONF_PWM_OUT_PIN;
    config_tcc.pins.wave_out_pin_mux[CONF_PWM_OUTPUT]    = CONF_PWM_OUT_MUX;

    tcc_init(&tcc_instance, CONF_PWM_MODULE, &config_tcc);

    tcc_set_compare_value(&tcc_instance,
            (enum tcc_match_capture_channel)CONF_PWM_CHANNEL, 8000*3/4);
    tcc_enable_circular_buffer_compare(&tcc_instance,
            (enum tcc_match_capture_channel)CONF_PWM_CHANNEL);

    tcc_enable(&tcc_instance);
}

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

    configure_tcc();

Workflow

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

   struct tcc_module tcc_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 TCC module.
   1. Create a TCC module configuration struct, which can be filled out to adjust the configuration of a physical TCC peripheral.

          struct tcc_config config_tcc;

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

          tcc_get_config_defaults(&config_tcc, CONF_PWM_MODULE);

      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 TCC settings to configure the counter width, wave generation mode, and the compare channel 0 value.

          config_tcc.counter.clock_prescaler = TCC_CLOCK_PRESCALER_DIV1024;
          config_tcc.counter.period = 8000;
          config_tcc.compare.wave_generation = TCC_WAVE_GENERATION_SINGLE_SLOPE_PWM;
          config_tcc.compare.match[CONF_PWM_CHANNEL] = (8000 / 4);

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

          config_tcc.pins.enable_wave_out_pin[CONF_PWM_OUTPUT] = true;
          config_tcc.pins.wave_out_pin[CONF_PWM_OUTPUT]        = CONF_PWM_OUT_PIN;
          config_tcc.pins.wave_out_pin_mux[CONF_PWM_OUTPUT]    = CONF_PWM_OUT_MUX;

   5. Configure the TCC module with the desired settings.

          tcc_init(&tcc_instance, CONF_PWM_MODULE, &config_tcc);

   6. Set to compare buffer value and enable circular of double buffered compare values.

          tcc_set_compare_value(&tcc_instance,
                  (enum tcc_match_capture_channel)CONF_PWM_CHANNEL, 8000*3/4);
          tcc_enable_circular_buffer_compare(&tcc_instance,
                  (enum tcc_match_capture_channel)CONF_PWM_CHANNEL);

   7. Enable the TCC module to start the timer and begin PWM signal generation.

          tcc_enable(&tcc_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 PWM wave is generated via the TCC module.

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