SAML21走起7：TC回调方式

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 

#define PWM_MODULE EXT2_PWM_MODULE

#define PWM_OUT_PIN EXT2_PWM_0_PIN

#define PWM_OUT_MUX EXT2_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();