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. 2.1.
  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. 2.2.
  Initialize the TCC configuration struct with the module's default values.
```
tcc_get_config_defaults(&config_tcc, TCC0);
```
  Note: This should always be performed before using the configuration struct to ensure that all values are initialized to known default settings.
3. 2.3.
  Alter the TCC settings to configure the GCLK source, prescaler, period and compare channel values.
```
config_tcc.counter.clock_source = GCLK_GENERATOR_1;
config_tcc.counter.clock_prescaler = TCC_CLOCK_PRESCALER_DIV64;
config_tcc.counter.period =   2000;
config_tcc.compare.match[0] =  900;
config_tcc.compare.match[1] =  930;
config_tcc.compare.match[2] = 1100;
config_tcc.compare.match[3] = 1250;
```
4. 2.4.
  Configure the TCC module with the desired settings.
```
tcc_init(&tcc_instance, TCC0, &config_tcc);
```
5. 2.5.
  Enable the TCC module to start the timer.
```
tcc_enable(&tcc_instance);
```

Configure the TCC callbacks.

3.1.

tcc_register_callback(&tcc_instance, tcc_callback_to_toggle_led,
        TCC_CALLBACK_OVERFLOW);
tcc_register_callback(&tcc_instance, tcc_callback_to_toggle_led,
        TCC_CALLBACK_CHANNEL_0);
tcc_register_callback(&tcc_instance, tcc_callback_to_toggle_led,
        TCC_CALLBACK_CHANNEL_1);
tcc_register_callback(&tcc_instance, tcc_callback_to_toggle_led,
        TCC_CALLBACK_CHANNEL_2);
tcc_register_callback(&tcc_instance, tcc_callback_to_toggle_led,
        TCC_CALLBACK_CHANNEL_3);

3.2.

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

tcc_enable_callback(&tcc_instance, TCC_CALLBACK_OVERFLOW);
tcc_enable_callback(&tcc_instance, TCC_CALLBACK_CHANNEL_0);
tcc_enable_callback(&tcc_instance, TCC_CALLBACK_CHANNEL_1);
tcc_enable_callback(&tcc_instance, TCC_CALLBACK_CHANNEL_2);
tcc_enable_callback(&tcc_instance, TCC_CALLBACK_CHANNEL_3);