SAM OSC8MHz Calibration Application.

#include <asf.h>
#include "conf_example.h"

Macros
#define	CALIBRATION_RESOLUTION CONF_CALIBRATION_RESOLUTION
	Resolution of the calibration binary divider; lower powers of two will reduce the calibration resolution. More...

#define	COMM_CAL_MAX 0x7F

#define	COMM_CAL_MIN 0x00

#define	FRANGE_CAL_MAX 0x03

#define	FRANGE_CAL_MIN 0x00
	OSC8M calibration info. More...

#define	REFERENCE_CLOCK GCLK_GENERATOR_3
	Calibration reference clock generator index. More...

#define	REFERENCE_CLOCK_HZ 32768
	Frequency of the calibration reference clock in Hz. More...

#define	TARGET_FREQUENCY 8000000
	Target OSC8M calibration frequency. More...

#define	TEMP_CAL_MAX 0x1F

#define	TEMP_CAL_MIN 0x00

#define	TEMP_CAL_OFFSET 0x07

Functions
static uint32_t	get_osc_frequency (void)
	Retrieves the current system clock frequency, computed from the reference clock. More...

int	main (void)

static void	setup_clock_out_pin (void)
	Set up the clock output pin so that the current system clock frequency can be monitored via an external frequency counter or oscilloscope. More...

static void	setup_events (struct events_resource *event)
	Set up the event system, linking the measurement and comparison timers so that events generated from the reference timer are linked to the measurement timer. More...

static void	setup_tc_channels (void)
	Set up the measurement and comparison timers for calibration. More...

static void	setup_tc_events (void)
	Set up the measurement and comparison timer events. More...

static void	setup_usart_channel (void)
	Set up the USART for transmit-only communication at a fixed baud rate. More...

Variables
static struct tc_module	tc_calib
	Software instance of the TC module used for calibration measurement. More...

static struct tc_module	tc_comp
	Software instance of the TC module used for calibration comparison. More...

static struct usart_module	usart_edbg
	Software instance of the USART upon which to transmit the results. More...

#define CALIBRATION_RESOLUTION CONF_CALIBRATION_RESOLUTION

Resolution of the calibration binary divider; lower powers of two will reduce the calibration resolution.

Referenced by get_osc_frequency(), and setup_tc_channels().

#define COMM_CAL_MAX 0x7F

Referenced by main().

#define COMM_CAL_MIN 0x00

Referenced by main().

#define FRANGE_CAL_MAX 0x03

Referenced by main().

#define FRANGE_CAL_MIN 0x00

OSC8M calibration info.

Referenced by main().

#define REFERENCE_CLOCK GCLK_GENERATOR_3

Calibration reference clock generator index.

Referenced by setup_tc_channels().

#define REFERENCE_CLOCK_HZ 32768

Frequency of the calibration reference clock in Hz.

Referenced by get_osc_frequency().

#define TARGET_FREQUENCY 8000000

Target OSC8M calibration frequency.

Referenced by main().

#define TEMP_CAL_MAX 0x1F

Referenced by main().

#define TEMP_CAL_MIN 0x00

Referenced by main().

#define TEMP_CAL_OFFSET 0x07

Referenced by main().

static uint32_t get_osc_frequency ( void )

static

Retrieves the current system clock frequency, computed from the reference clock.

Returns: Current system clock frequency in Hz.

References CALIBRATION_RESOLUTION, REFERENCE_CLOCK_HZ, tc_calib, tc_clear_status(), tc_comp, TC_COMPARE_CAPTURE_CHANNEL_0, tc_get_capture_value(), tc_get_status(), tc_start_counter(), and TC_STATUS_CHANNEL_0_MATCH.

Referenced by main().

static void setup_clock_out_pin ( void )

static

Set up the clock output pin so that the current system clock frequency can be monitored via an external frequency counter or oscilloscope.

References CONF_CLOCK_PIN_MUX, CONF_CLOCK_PIN_OUT, system_pinmux_config::mux_position, system_pinmux_get_config_defaults(), and system_pinmux_pin_set_config().

Referenced by main().

static void setup_events ( struct events_resource * event )

static

Set up the event system, linking the measurement and comparison timers so that events generated from the reference timer are linked to the measurement timer.

References CONF_EVENT_GENERATOR_ID, CONF_EVENT_USED_ID, events_config::edge_detect, events_allocate(), events_attach_user(), EVENTS_EDGE_DETECT_RISING, events_get_config_defaults(), EVENTS_PATH_SYNCHRONOUS, events_config::generator, and events_config::path.

Referenced by main().

static void setup_tc_channels ( void )

static

Set up the measurement and comparison timers for calibration.

Configure the measurement timer to run from the CPU clock, in capture mode.
Configure the reference timer to run from the reference clock, generating a capture every time the calibration resolution count is met.

References CALIBRATION_RESOLUTION, tc_config::clock_prescaler, tc_config::clock_source, tc_16bit_config::compare_capture_channel, CONF_TC_MEASUREMENT, CONF_TC_REFERENCE, tc_config::counter_16_bit, tc_config::counter_size, tc_config::enable_capture_on_channel, REFERENCE_CLOCK, tc_calib, TC_CLOCK_PRESCALER_DIV1, tc_comp, TC_COUNTER_SIZE_16BIT, TC_COUNTER_SIZE_32BIT, tc_get_config_defaults(), tc_init(), TC_WAVE_GENERATION_NORMAL_FREQ, and tc_config::wave_generation.

Referenced by main().

static void setup_tc_events ( void )

static

Set up the measurement and comparison timer events.

Configure the reference timer to generate an event upon comparison match with channel 0.
Configure the measurement timer to trigger a capture when an event is received.

References tc_events::generate_event_on_compare_channel, tc_events::on_event_perform_action, tc_calib, tc_comp, tc_enable(), and tc_enable_events().

Referenced by main().

static void setup_usart_channel ( void )

static

Set up the USART for transmit-only communication at a fixed baud rate.

References usart_config::baudrate, EDBG_CDC_MODULE, EDBG_CDC_SERCOM_MUX_SETTING, EDBG_CDC_SERCOM_PINMUX_PAD0, EDBG_CDC_SERCOM_PINMUX_PAD1, EDBG_CDC_SERCOM_PINMUX_PAD2, EDBG_CDC_SERCOM_PINMUX_PAD3, usart_config::mux_setting, usart_config::pinmux_pad0, usart_config::pinmux_pad1, usart_config::pinmux_pad2, usart_config::pinmux_pad3, usart_edbg, usart_enable(), and usart_get_config_defaults().