Mbed OS Reference | us_ticker

 
 /** \addtogroup hal */
 /** @{*/
 /* mbed Microcontroller Library
  * Copyright (c) 2006-2015 ARM Limited
  * SPDX-License-Identifier: Apache-2.0
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 #ifndef MBED_US_TICKER_API_H
 #define MBED_US_TICKER_API_H
 
 #include <stdint.h>
 #include "hal/ticker_api.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /**
  * \defgroup hal_us_ticker Microsecond Ticker
  * Low level interface to the microsecond ticker of a target
  *
  * # Defined behavior
  * * Has a reported frequency between 250KHz and 8MHz - Verified by test ::us_ticker_info_test
  * * Has a counter that is at least 16 bits wide - Verified by test ::us_ticker_info_test
  * * All behavior defined by the @ref hal_ticker_shared "ticker specification"
  *
  * # Undefined behavior
  * * See the @ref hal_ticker_shared "ticker specification"
  *
  * @see hal_us_ticker_tests
  *
  * # Compile-time optimization macros
  *
  * To permit compile-time optimization, particularly of wait_us, the following macros should
  * be defined by a target's device.h:
  *
  * US_TICKER_PERIOD_NUM, US_TICKER_PERIOD_DEN: These denote the ratio (numerator, denominator)
  * of the ticker period to a microsecond. For example, an 8MHz ticker would have NUM = 1, DEN = 8;
  * a 1MHz ticker would have NUM = 1, DEN = 1; a 250kHz ticker would have NUM = 4, DEN = 1.
  * Both numerator and denominator must be 16 bits or less.
  *
  * US_TICKER_MASK: The value mask for the ticker - eg 0x07FFFFFF for a 27-bit ticker.
  *
  * If any are defined, all 3 must be defined, and the macros are checked for consistency with
  * us_ticker_get_info by test ::us_ticker_info_test.
 
  * @{
  */
 
 /**
  * \defgroup hal_us_ticker_tests Microsecond Ticker tests
  * Tests to validate the proper implementation of the microsecond ticker
  *
  * To run the microsecond ticker hal tests use the command:
  *
  *     mbed test -t <toolchain> -m <target> -n tests-mbed_hal-common_ticker*,tests-mbed_hal-us_ticker*
  *
  * @see hal_ticker_tests
  *
  */
 
 /**
  * \defgroup hal_ticker_shared Ticker Hal
  * Low level interface to the ticker of a target
  *
  * # Defined behavior
  * * The function ticker_init is safe to call repeatedly - Verified by test ::ticker_init_test
  * * The function ticker_init allows the ticker to keep counting and disables the ticker interrupt - Verified by test ::ticker_init_test
  * * Ticker frequency is non-zero and counter is at least 8 bits - Verified by ::ticker_info_test
  * * The ticker rolls over at (1 << bits) and continues counting starting from 0 - Verified by ::ticker_overflow_test
  * * The ticker counts at the specified frequency +- 10% - Verified by ::ticker_frequency_test
  * * The ticker increments by 1 each tick - Verified by ::ticker_increment_test
  * * The ticker interrupt fires only when the ticker times increments to or past the value set by ticker_set_interrupt.
  * Verified by ::ticker_interrupt_test and ::ticker_past_test
  * * It is safe to call ticker_set_interrupt repeatedly before the handler is called - Verified by ::ticker_repeat_reschedule_test
  * * The function ticker_fire_interrupt causes ticker_irq_handler to be called immediately from interrupt context -
  * Verified by ::ticker_fire_now_test
  * * The ticker operations ticker_read, ticker_clear_interrupt, ticker_set_interrupt and ticker_fire_interrupt
  * take less than 20us to complete - Verified by ::ticker_speed_test
  * * The ticker operations ticker_init and ticker_read are atomic.
  *
  * # Undefined behavior
  * * Calling any function other than ticker_init before the initialization of the ticker
  * * Whether ticker_irq_handler is called a second time if the time wraps and matches the value set by ticker_set_interrupt again
  * * Calling ticker_set_interrupt with a value that has more than the supported number of bits
  * * Calling any function other than us_ticker_init after calling us_ticker_free
  *
  * # Potential bugs
  * * Drift due to reschedule - Verified by ::ticker_repeat_reschedule_test
  * * Incorrect overflow handling of timers - Verified by ::ticker_overflow_test
  * * Interrupting at a time of 0 - Verified by ::ticker_overflow_test
  * * Interrupt triggered more than once - Verified by ::ticker_interrupt_test
  *
  * @ingroup hal_us_ticker
  * @ingroup hal_lp_ticker
  */
 
 /**
  * \defgroup hal_ticker_tests Ticker Tests
  * Tests to validate the proper implementation of a ticker
  *
  * To run the ticker hal tests use the command:
  *
  *     mbed test -t <toolchain> -m <target> -n tests-mbed_hal-common_ticker*
  *
  * @ingroup hal_us_ticker
  * @ingroup hal_lp_ticker
  */
 
 
 typedef void (*ticker_irq_handler_type)(const ticker_data_t *const);
 
 /** Set ticker IRQ handler
  *
  * @param ticker_irq_handler IRQ handler to be connected
  *
  * @return previous ticker IRQ handler
  *
  * @note by default IRQ handler is set to ::ticker_irq_handler
  * @note this function is primarily for testing purposes and it's not required part of HAL implementation
  *
  */
 ticker_irq_handler_type set_us_ticker_irq_handler(ticker_irq_handler_type ticker_irq_handler);
 
 /** Get ticker's data
  *
  * @return The microsecond ticker data
  */
 const ticker_data_t *get_us_ticker_data(void);
 
 
 /** The wrapper for ticker_irq_handler, to pass us ticker's data
  *
  */
 void us_ticker_irq_handler(void);
 
 /* HAL us ticker */
 
 /** Initialize the ticker
  *
  * Initialize or re-initialize the ticker. This resets all the
  * clocking and prescaler registers, along with disabling
  * the compare interrupt.
  *
  * @note Initialization properties tested by ::ticker_init_test
  *
  * Pseudo Code:
  * @code
  * void us_ticker_init()
  * {
  *     // Enable clock gate so processor can read TIMER registers
  *     POWER_CTRL |= POWER_CTRL_TIMER_Msk;
  *
  *     // Disable the timer and ensure it is powered down
  *     TIMER_CTRL &= ~(TIMER_CTRL_ENABLE_Msk | TIMER_CTRL_COMPARE_ENABLE_Msk);
  *
  *     // Configure divisors
  *     uint32_t prescale = SystemCoreClock / 1000000;
  *     TIMER_PRESCALE = prescale - 1;
  *     TIMER_CTRL |= TIMER_CTRL_ENABLE_Msk;
  *
  *     // Install the interrupt handler
  *     NVIC_SetVector(TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
  *     NVIC_EnableIRQ(TIMER_IRQn);
  * }
  * @endcode
  */
 void us_ticker_init(void);
 
 /** Deinitialize the us ticker
  *
  * Powerdown the us ticker in preparation for sleep, powerdown, or reset.
  *
  * After this function is called, no other ticker functions should be called
  * except us_ticker_init(), calling any function other than init is undefined.
  *
  * @note This function stops the ticker from counting.
  *
  * Pseudo Code:
  * @code
  * uint32_t us_ticker_free()
  * {
  *     // Disable timer
  *     TIMER_CTRL &= ~TIMER_CTRL_ENABLE_Msk;
  *
  *     // Disable the compare interrupt
  *     TIMER_CTRL &= ~TIMER_CTRL_COMPARE_ENABLE_Msk;
  *
  *     // Disable timer interrupt
  *     NVIC_DisableIRQ(TIMER_IRQn);
  *
  *     // Disable clock gate so processor cannot read TIMER registers
  *     POWER_CTRL &= ~POWER_CTRL_TIMER_Msk;
  * }
  * @endcode
  *
  */
 void us_ticker_free(void);
 
 /** Read the current counter
  *
  * Read the current counter value without performing frequency conversions.
  * If no rollover has occurred, the seconds passed since us_ticker_init()
  * was called can be found by dividing the ticks returned by this function
  * by the frequency returned by ::us_ticker_get_info.
  *
  * @return The current timer's counter value in ticks
  *
  * Pseudo Code:
  * @code
  * uint32_t us_ticker_read()
  * {
  *     return TIMER_COUNT;
  * }
  * @endcode
  */
 uint32_t (us_ticker_read)(void);
 
 /** Set interrupt for specified timestamp
  *
  * @param timestamp The time in ticks to be set
  *
  * @note no special handling needs to be done for times in the past
  * as the common timer code will detect this and call
  * us_ticker_fire_interrupt() if this is the case
  *
  * @note calling this function with timestamp of more than the supported
  * number of bits returned by ::us_ticker_get_info results in undefined
  * behavior.
  *
  * Pseudo Code:
  * @code
  * void us_ticker_set_interrupt(timestamp_t timestamp)
  * {
  *     TIMER_COMPARE = timestamp;
  *     TIMER_CTRL |= TIMER_CTRL_COMPARE_ENABLE_Msk;
  * }
  * @endcode
  */
 void us_ticker_set_interrupt(timestamp_t timestamp);
 
 /** Disable us ticker interrupt
  *
  * Pseudo Code:
  * @code
  * void us_ticker_disable_interrupt(void)
  * {
  *     // Disable the compare interrupt
  *     TIMER_CTRL &= ~TIMER_CTRL_COMPARE_ENABLE_Msk;
  * }
  * @endcode
  */
 void us_ticker_disable_interrupt(void);
 
 /** Clear us ticker interrupt
  *
  * Pseudo Code:
  * @code
  * void us_ticker_clear_interrupt(void)
  * {
  *     // Write to the ICR (interrupt clear register) of the TIMER
  *     TIMER_ICR = TIMER_ICR_COMPARE_Msk;
  * }
  * @endcode
  */
 void us_ticker_clear_interrupt(void);
 
 /** Set pending interrupt that should be fired right away.
  *
  * The ticker should be initialized prior calling this function.
  *
  * Pseudo Code:
  * @code
  * void us_ticker_fire_interrupt(void)
  * {
  *     NVIC_SetPendingIRQ(TIMER_IRQn);
  * }
  * @endcode
  */
 void us_ticker_fire_interrupt(void);
 
 /** Get frequency and counter bits of this ticker.
  *
  * Pseudo Code:
  * @code
  * const ticker_info_t* us_ticker_get_info()
  * {
  *     static const ticker_info_t info = {
  *         1000000,    // 1 MHz
  *         32          // 32 bit counter
  *     };
  *     return &info;
  * }
  * @endcode
  */
 const ticker_info_t *us_ticker_get_info(void);
 
 /**@}*/
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif
 
 /** @}*/
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